Electric Vehicle Conversion of a Foldable Motorbike

Bjarni Freyr Gudmundsson, s042859

Design state

Synthesis & Special Project, Juni 2010

Bjarni Freyr Gudmundsson, s042859

Electric Vehicle Conversion of a Foldable Motorbike

Design state

Synthesis & Special Project, Juni 2010

Electric Vehicle Conversion of a Foldable Motorbike,Design state

This report was prepared by Bjarni Freyr Gudmundsson, s042859

Supervisors Esben Larsen

Department of Electrical Engineering Centre for Electric Technology (CET) Technical University of Denmark Elektrovej building 325 DK-2800 Kgs. Lyngby Denmark

www.elektro.dtu.dk/cet Tel: (+45) 45 25 35 00 Fax: (+45) 45 88 61 11 E-mail: [email protected]

Release date: 31. August 2010 Category: 2 (conﬁdential) Edition: First Comments: This report is part of the requirements to achieve the Master of Science in Engineering (M.Sc.Eng.) at the Technical University of Denmark. This report represents 20 ECTS points. Rights: c Bjarni Freyr Gudmundsson, 2008

Preface

This report is a part of fulfillment requirements for acquiring the course 31910 Synthesis in electrotechnology and a 10 ECTS credit special course. The aim of the project is to get familiar with electric vehicle technology and to gain understanding on what the major electrical components are needed to propel the vehicle in sophisticated way. Furthermore, the author of the paper will use this project to gain the understanding on the behavior of different DC motor types. The author wants to thank Esben Larsen for all the long discussions we had regarding the project and for the interest shown on the subject. Joachim Hjerl, David Koch Mouritzen and Christian Rottbøll at CityRiders are thanked for bringing the project to DTU, providing the opportunity of this project and thank you for being so flexible when I needed the moped for testing and measurements. Bogi Bech Jensen is thanked for the valuable comments and suggestions regarding motor types and properties. Finally, thanks to my lovingly Edda and my beautiful Freydis for the understanding and moral support after all the long working days during the project. The project was done over the summer period of 2010 and is a part of the authors MSc programme.

Abstract

Electric vehicles have been come more and more popular discussion and seems to be one of the most developing technology today. The society seems to be more than before aware of the influences on nature and environment combustion propelled vehicles are causing. The electric vehicle seems to be something everyone knows of but no one uses and the negative public image of electric vehicle has been less over the recent years. In this project the investigation of electric vehicle conversion is done. An Italian made foldable combustion moped is used as a test subject for the project. The main effecting factors when comes to challenges met by electric vehicle designers are realized and discussed. Evaluation leads to the optimal selection on main electrical components in the electrical mopeds drivetrain. Simulation by MATLAB mathematical modeling is done using data from the electrical components considered to give the vehicle the optimal performance. Variable factors in the vehicle design will be manipulated to realize the effects of the different factors on vehicle performance. The results of MATLAB mathematical modeling show enhanced acceleration and top speed characteristics than on current combustion mope.

Contents

List of Figures ix

List of Tables xiii

1 Introduction 1 1.1 Background ...... 2 1.2 ProblemFormulation...... 2 1.3 DiBlasi’sR7speciﬁcations ...... 3

Nomenclature 3

2 Mechanics 9 2.1 Forceoftractiveeﬀort ...... 10 2.2 Forceofaerodynamicdrag...... 11 2.3 Forceofrollingresistance ...... 13 2.4 Forceofhillclimbing...... 15 2.5 Forceofacceleration ...... 15 2.5.1 Forceoflinearacceleration ...... 16 2.5.2 Forceofcircularacceleration ...... 16 2.6 Thetotaltractiveeﬀort ...... 17

3 Mechanical Transmission 19 3.1 BeltsandPulleys...... 19 3.1.1 V-belts ...... 20 3.1.2 Flatbelts ...... 21 3.1.3 PolyV-belts ...... 22 3.1.4 TimingBelts ...... 22 3.1.5 Lossesinbelttransmissions ...... 23 3.2 Gearsratio ...... 24 3.3 Currenttransmissionsystem ...... 26 3.4 Evaluationofthetransmissionsystem ...... 27

4 DC motors 29 4.1 Brushed DC permanent magnet electric motor ...... 30 4.1.1 Torque...... 32 4.1.2 Controls...... 34 4.1.3 Eﬃciency ...... 35 4.1.4 Regenerativebraking...... 38 4.1.5 LEM-130 ...... 41 4.1.6 PMG132 ...... 45 4.2 WoundﬁeldDCelectricmotors ...... 47 4.2.1 Series ...... 48 4.2.2 Shunt ...... 52 4.2.3 Separatelyexcited ...... 54 4.3 Brushless DC permanent magnet electric motor ...... 55 4.3.1 Wheelhubmotors ...... 58 4.3.2 BLDCsectiondiscussion...... 65 4.4 Motorcomparison ...... 66

5 Battery 69 5.1 Li-ion ...... 71 5.1.1 BatteryManagementSystem ...... 71 5.1.2 Types ...... 72 5.2 Batterydesign ...... 75

6 Modeling of the electric moped 77 6.1 Accelerationcharacteristics ...... 77 6.2 ECE-47circlesimulation...... 79 6.3 LFPLi-ionvoltagecharacteristics...... 80 6.4 Rangetest...... 81

7 Discussion 89

8 Conclusion 91

References 93

Appendix 97

A Matlab codes 97 A.1 Acceleratingcharacteristics ...... 97 A.2 Eﬃciencymap ...... 98 A.3 ECE-47circlesimulation...... 99 A.4 LFPLi-ionvoltagecharacteristics...... 100 A.5 Onetestcycle...... 101 A.6 Rangesimulation ...... 104

B Motor and battery data 107 B.1 LEM-130 from Lynch Motor Company LTD...... 109 B.1.1 MechanicalDrawing ...... 109 B.2 PMG132fromPERMMOTOR ...... 110 B.2.1 MechanicalDrawing ...... 110 B.2.2 Motor-curves ...... 111 B.3 AMGfromIskra ...... 115 viii

B.4 AdvancedMotor&Drives ...... 117 B.4.1 140-07-4001 ...... 117 B.4.2 A00-4009 ...... 121 B.5 MW-16C BLDC hub motor from Golden motor ...... 125 B.5.1 MechanicalDrawing ...... 125 B.5.2 Motorcurvesanddata...... 126 B.6 HDM105E10-51SfromSEM...... 128 B.7 LiFePObatteryfromGoldMotrrs ...... 131

C Motor Comparison 133

D Component ﬁttings into frame 137 D.1 LEM-130 from Lynch Motor Company LTD...... 137 D.2 PMG132fromPERMMOTORGMBHD...... 138 D.3 HDM105E10-51SfromSEM...... 139 D.4 LFPbatteryfromGoldenMotors ...... 141

E E-mails 143 E.1 AdvancedMotor&Drives ...... 143

F Figures of the moped 147 List of Figures

1.1 The Di Blasi moped at folded and unfolded state, from [12] . 4 1.2 Data results of mopeds timing experiment...... 4 1.3 Plotted results from mopeds timing experiment...... 4

2.1 The forces effecting the moped tractive effort...... 9 2.2 Themopedsdrivetrain...... 10 2.3 The frontal areal of the moped among driver ...... 12 2.4 Difference of contact area shape of narrow and wide tire, from [15]...... 14 2.5 Tires with very different rolling resistance, from [5]...... 14 2.6 A figure of the current tire used on the Di Blasi mopeds. . . . 15

3.1 AnexampleofaV-belt ...... 21 3.2 Anexampleofaflatbelt ...... 21 3.3 AnexampleofaPolyV-belt ...... 22 3.4 AnExampleofatimingbelt ...... 23 3.5 The efficiency of different belts at 1450[rpm]. ”Tendrem” is timing belt, ”Fladrem”is flat belt, ”Poly-V rem”is poly V-belt and ”Smalkilerem” is V-belt, figure from [29]...... 23 3.6 The moped’s accelerating characteristics for different gear ratios 25 3.7 The transmission currently on the Di Blasi moped ...... 26 x LIST OF FIGURES

3.8 The mopeds current transmission system...... 27

4.1 Brushed DC permanent magnet electric motor, from [11]... 30 4.2 The magnetic force rotating the armature. The ”X”marks the current direction from the reader and • marks the direction towards the reader, from [35]...... 31 4.3 A theoretical description of a DC motor torque-speed characteristics...... 34 4.4 Eddy current in a solid and layered armature, from [30] ... 37 4.5 An example of efficiency map of a typical brushed DC per- manentmagnetelectricmotor...... 39 4.6 Regenerative braking system with a DC/DC converter, from [31]...... 40 4.7 Increase in fuel efficiency of EVT scooter with varying size of ultracapacitor energy storage. Note: this is useful energy storage, not ultracapacitor maximum energy storage. Also, the motor/generator is rated at 1.5 kW as supplied by manufacturer. Figure from [23] ...... 41 4.8 Dual braking system used on the VX-1 electric motorbike, from [16]...... 42 4.9 LEM-130 motor from Lynch Motor Company Ltd. approx weight3kg...... 42 4.10 LEM-130 motors torque-speed characteristics ...... 43 4.11 The moped’s acceleration characteristics using LEM-130 motor 45 4.12 The moped’s acceleration characteristics using PMG 132 motor 46 4.13 Wound field motor’s torque-speed characteristics ...... 48 4.14 Series connected wound field DC electric motor ...... 49 4.15 A typical torque-speed and torque-current characteristics of a series motor, from [40]...... 50 4.16 Modeling the mopeds top speed at different gear ratios using the 140-07 motor from Advanced Motors Inc...... 52 4.17 Parallel connected wound field DC electric motor ...... 53 4.18 A typical torque-speed and torque-current characteristics of a shunt motor, from [40]...... 54 LIST OF FIGURES xi

4.19 The separately excited DC motor has independent input terminals for the wound ﬁeld and the armature ...... 54

4.20 TheconstructionoftheBLDCmotor...... 56

4.21 ThebasicoperationofBLDCmotor ...... 57

4.22 VoltageappliedtotheBLDCmotor ...... 57

4.23 The mopeds maximum speed capabilities using the HDM mo- torfromSEM...... 59

4.24 BLDChubmotor...... 60

4.25 Modeling the mopeds top speed at diﬀerent gear ratios using the MW-16C BLDC hub motor from Golden Motors . . . . . 62

4.26 Modeling the mopeds acceleration characteristics using the MW-16C BLDC hub motor from Golden Motors ...... 63

4.27 Modeling the mopeds speed capabilities at diﬀerent gear ratios using the EVT3kW BLDC hub motor from EVT . . . . . 64

4.28 Modeling the mopeds speed capabilities at diﬀerent gear ratios using the MW12B BLDC hub motor from Golden Motors 65

4.29 Cost comparison of brushed DC, series and BLDC motors. Where the red, blue and green lines represent the average ﬁttedvalue...... 67

4.30 Weight comparison of brushed DC, series and BLDC motors. Where the red, blue and green lines represent the average ﬁttedvalue...... 67

4.31 Comparison of Series/shunt and BLDC motor, from [38]... 68

5.1 A123 System’s nLFP battery in DeWalt power tool battery unit...... 75

5.2 Batteryunitsandbatterycells ...... 76

6.1 Modeling the mopeds speed capabilities at diﬀerent gear ratios using the BLDC HDM105 motor from SEM ...... 78

6.2 Modeling the mopeds speed capabilities at diﬀerent gear ratios using the BLDC HDM105 motor from SEM ...... 79

6.3 Discharge voltage of LFP Li-ion battery at diﬀerent temperatures, ﬁgure from phostechlithium.com ...... 80 xii LIST OF FIGURES

6.4 Discharge voltage of LFP Li-ion battery used in the range simulation...... 80 6.5 Flowchartoftherangesimulation...... 82 6.6 Results from ﬁrst range simulation, data used for this simulation is shown in table6.1...... 83 6.7 Results from range simulation when varying the number of batteries. Red: One battery, Black: Two batteries and Blue: Three batteries, other variables are according to table 6.1. . 84 6.8 Results from range simulation when varying the drag coef- ﬁcient. Red:Cd = 1.1 Black:Cd = 0.9 Blue:Cd = 0.6, other variables are according to table 6.1...... 85

6.9 Results from range simulation when varying the weight. Red:Cd = 150[kg] Black:Cd = 100[kg] Blue:Cd = 50[kg], other variables are according to table 6.1...... 85 6.10 Results from range simulation when varying the tires rolling resistance. Black:µrr = 0.015 Blue:µrr = 0.005, other variables are according to table 6.1...... 86 6.11 Results from range simulation when optimizing all variables. Red: Optimized values with one battery Black: Original values with two batteries Blue: Optimized values with two batteries...... 87

B.1 AMGIskramotordata...... 115

D.1 The LEM-130 fitted into frame, side view. Motor size has beenscaled...... 137 D.2 The LEM-130 fitted into frame, bottom view. Motor size has beenscaled...... 138 D.3 The PMG 132 fitted into frame, side view. Motor size has been scaled. Red area is where motor collides with tire, motor doesnotfitintotheframe...... 139 D.4 The HDM105E10-51S motor from SEM fitted into frame, bot- tomview. Motorsizehasbeenscaled...... 140 D.5 The HDM105E10-51S motor from SEM fitted into frame, side view. Motorsizehasbeenscaled...... 140 D.6 An LFP battery from GoldenMotors fitted into frame, top view. Batterysizehasbeenscaled...... 141 LIST OF FIGURES xiii

D.7 An LFP battery from GoldenMotors ﬁtted into frame, side view. Batterysizehasbeenscaled...... 142

F.1 The motors total length must be less than 230[mm]...... 147 xiv LIST OF FIGURES List of Tables

5.1 General characteristics of diﬀerent Li-ion battery types. . . . 73 5.2 General characteristics of diﬀerent Li-ion battery types. . . . 74

6.1 Datausedintheﬁrstrangesimulation ...... 81 6.2 Data used in the optimized design range simulation ...... 86 xvi LIST OF TABLES Chapter 1

Introduction

In the this report the investigation on electric vehicle conversation of a foldable moped1 in possession of CityRiders will be done. Earlier this year the owners of CityRider, a company that specializes in rental personal chauf- feur, approached DTU with an idea of the vehicle conversation of a foldable mopeds used by the companies personal chauffeurs. In the following sections focus will be on the different parts of the mopeds drivetrain. The report will follow a line with mechanical perspective, where evaluation and discussions on each part will take place. The report will issue, in the following order, the mopeds tires, transmission, electric motor and battery. Mechanical evaluation and effects of the different components within the mopeds drivetrain will be done. Components causing the major limitation regarding vehicles speed and range will be discussed and evaluated. A realization on the main electrical parts of the drivetrain will be done, followed by evaluation on different types that lead to a selection on the considered optimum selection. MATLAB programmed mathematical modeling of the foldable electric vehicle will be done in accordance with European driving cycle standard to given an idea of the range, acceleration and top speed capabilities of the electric moped. An evaluation on what parts will be needed to implement the electric vehicle conversion, among the cost of the main electrical parts needed for the vehicles drivetrain. The evaluation of projects design will be based in the process of realization, analysis and modeling the vehicle.

1Moped is low-powered motorcycle, with minimal licensing requirements. 2 Introduction

1.1 Background

CityRiders are currently using an Italian made foldable moped of type R7 from Di Blasi Industriale. CityRiders has several years experience using the combustion powered mopeds for personal chauﬀeur rental service. The mopeds foldability concept is considered to be very well functioning, the engine is however somewhat less reliable. CityRiders are considering to convert the combustion powered moped to an all electric powered moped. CityRid- ers approached DTU with the idea earlier this year where the projects was considered to be suitable as a student project.

1.2 Problem Formulation

The aim of the project is to come up with a design regarding components needed to convert the currently existing combustion engine motorbike to an all-electric motorbike. Suitable components, such as energy storage system and motor, need to be found that meets requirements and optimize cost and performance. The components size and weight are to be issued and are to ﬁt into the currently existing motorbike frame.

The moped should be capable of similar acceleration as moped is capable of with combustion engine and a top speed of 45-55[km/h]2. Range should be optimized, same time the weight and cost have to be minimized. Electrical system that is currently on CityRiders’ motorcycle is assumed to be fully functional and will therefore not be considered in this project. A power supply to the system must though be applied.

2As an request from CityRiders 1.3 Di Blasi’s R7 speciﬁcations 3

1.3 Di Blasi’s R7 speciﬁcations

Here the Bi Blasi’s R7 mopeds speciﬁcations are listed, the speciﬁcations are also found on Di Blasi’s web page [14]. Dimensions Overall length when unfolded ℓOA unf. 128.0[cm] Wheelbase when unfolded ℓWB unf. 93.5[cm] Width when unfolded ℓW unf. 57.5[cm] Length when folded ℓL fold 78.0[cm] Width when folded ℓW fold 37.0[cm] Height when folded ℓH fold 61.0[cm] Rim size (front & rear) drim 12.7[cm] (5”) Tire diameter (front & rear) dtire 15.5[cm] Engine Maximum power PCE max 0.86[kW ] Maximum torque τCE max 2.56[Nm] Transmission (Prim:V-belt, Sec:Timing belt) Minratioofprimarydrive 1:1.577 Maxratioofprimarydrive 1:3.736 Ratioofsecondarydrive 1:4.636 (22/102) Other

Unladen mass munlade 29.8[kg] El. equipment VNomEE 12.0[V ] PNomEE 65.0[W ] Tank capacity ltank 2.8[L] (3quarts) Fuelconsumption FC 35.0[km/L] Maximum speed υmax 12.5[m/s] (45.0[km/h])

Measurements where done to realize the mopeds acceleration characteristics. Fifty runs where timed, five runs for each ten meters. Optimally the measurements would have been done in several continuous runs with time measurements every 5-10[m]. This was not possible at this time due to cir- cumstances and available manpower. The results are to give an idea of the acceleration capabilities of the combustion powered moped. Figure 1.2 shows a table of the measurements made. Each length was timed in five separate runs, AV Gt displays the average time in seconds from the five runs and AV G 3 mid and red values displays the average and the three mid values, where the lowest and larges value have been excluded. The results of experiment show the combustion powered mopeds capabilities of reaching appr. 7.8[m/s] or 28.1[km/h] in 12.7[s]. 4 Introduction

(a) Folded (b) Unfolded

Figure 1.1: The Di Blasi moped at folded and unfolded state, from [12]

Figure 1.2: Data results of mopeds timing experiment.

Figure 1.3: Plotted results from mopeds timing experiment. Nomenclature

.ωa Subscript refers to angular acceleration, page 10

.ad Subscript refers to aerodynamic drag, page 10

.hc Subscript refers to an hill climb, page 10

.la Subscript refers to a linear acceleration, page 10

.rr Subscript refers to rolling resistance, page 10

.te Subscript refers to tractive eﬀort, page 9

.em Subscript refers to the electric motor, page 11

α Theangleofinclineplane,page9 [rad]

◦ αtemp Temperaturecoeﬃcient,page36 [1/ C]

ℓ Length , page 3 [m]

ηm Motor eﬃciency, page 38

ηcon Eﬃciency of a converter, page 40

µrr The tires rolling resistance, page 13

ωa The armatures angular velocity. , page 33 [m/s]

ωc Motorscriticalangularvelocity,page24 [rad/s]

φ Electricﬂuxoverasurface,page32 [V m]

◦ ρ0 A conductors resistivity at 0 C , page 36 [Ω · m]

3 ρAIR Thedensityofair,page11 [kg/m ] 6 Introduction

τ Torque , page 3 [Nm]

υ Speed , page 3 [m/s]

υcon The velocity of a conductor through a magnetic ﬁeld , page 33[m/s] ̟ Circularacceleration,page16 [m/s2]

A Themoped’sanddrive’sfrontarea,page11 [m2] a Acceleration , page 16 [m/s2]

B Flux density , page 32 [T ]

Cd The moped’s drag coeﬃcient, page 11 d Diameter, page 3 [m]

Eb VoltageduetothebackEMF,page33 [V ]

Es Voltage source , page 31 [V ] F Force , page 9 [N]

Fcon Forceactingonaconductor,page32 [N] G Gear ratio, page 11

I Electric current , page 32 [A]

J Momentofinertia,page16 [kg · m2]

Km Motor constant, page 32 l Volume , page 3 [L] m Mass , page 3 [kg] nlay Number of layers, page 37 nturn Numberofturns,page32 [turns] P Power , page 3 [W ]

Pcl Conductor losses , page 36 [W ]

Pfr Powerlossduetomechanicalfriction,page36 [W ]

Pil Iron losses , page 38 [W ]

Pin Input power , page 38 [W ]

Ploss Power loss , page 38 [W ] 1.3 Di Blasi’s R7 speciﬁcations 7

Pout Output power , page 38 [W ]

Pwp Power loss due to windage , page 36 [W ] r Radius , page 11 [m] r1or2 Thesprockets/pulleysradius,page11 [m]

Ra Armatureresistance,page31 [Ω] rcoil Coil radius , page 32 [m] S Tirescontactareatotheroad,page13 [m2]

T Temperature , page 36 [◦C]

V Voltage , page 3 [V ]

BLDC Brushless direct current motor, page 55

CVT Continuously Variable Transmission, page 26

EMC Electronically commutated motor, page 57

EMF Electromotive force, page 33

FC Fuelconsumption,page3 [km/L]

NTP Normal Temperature and Pressure, page 11 8 Introduction Chapter 2

Mechanics

Figure 2.1: The forces eﬀecting the moped tractive eﬀort.

The pulling force exerted by the mopeds wheel to the ground is called a tractive effort, Fte. The mopeds motor needs to be capable of providing enough torque to the wheel to overcome forces effecting the moped’s maneuverability, see figure 2.1. A moped of a mass m, proceeding at a velocity υ, up a slope α needs to overcome the following [31, 39]: 10 Mechanics

• The aerodynamic drag

• The rolling resistance

• The mopeds weight acting down the slope

• The force need to accelerate the moped, if velocity is not constant

The total tractive eﬀort must therefore be a sum of all forces caused by the factors above:

Fte = Fad + Frr + Fhc + Fla + Fωa (2.1) where

Fad = the force of aerodynamic drag [Nm]

Frr = the force of rolling resistance [Nm]

Fhc = the force of hill climbing [Nm]

Fla = the force of linear acceleration [Nm]

Fωa = the force of circular acceleration [Nm]

It is to be noted that when the moped is reducing velocity the forces of acceleration, Fla and Fωa, are negative. When the the moped is going down hill, the force of hill climbing is negative. In the following sections the diﬀerent forces are introduced and explained how they eﬀect the moped’s maneuverability.

2.1 Force of tractive eﬀort

Figure 2.2: The mopeds drivetrain. 2.2 Force of aerodynamic drag 11

The force of tractive eﬀort can be described as a function of tire radius rtire and the moped’s electric motor torque τem. First the relations of the motor’s torque and wheel’s torque τtire needs to be deﬁned:

r1 · τem = r2 · τtire r2 · τtire τem = (2.3) r1 where

r1 = the motor’s pulley/sprocket radius [mm]

r2 = the tire’s pulley/sprocket radius [mm]

The ratio of the transmission’s sprockets/pulleys is deﬁned as G = r1/r2, therefore equation 2.3 can be written as:

τ τ = tire em G ⇔ τtire = τem · G

⇔ Fte · rtire = τem · G τem · G ⇔ Fte = (2.5) rtire

2.2 Force of aerodynamic drag

The air drag is a resistance force that air exerts on the moped and it’s driver when moving through the it, this force is called the force of aerodynamic drag 2 Fad. Fad is proportional to the vehicles squared velocity υ , and depends on the air density ρAIR, the front area of the moving part (in this case the mopeds and the drivers front area) A and the drag coeﬃcient Cd. The following equation expresses the force of aerodynamic darg:

1 F = · ρ · A · C · υ2 (2.6) ad 2 AIR d The air density varies with temperature, pressure and humidity. In this report the value of air density is obtained from [17] where it is given a value 3 of ρAIR = 1.20[kg/m ] at Normal Temperature and Pressure (NTP). The front areal of the moped and it’s driver can be estimated by measurements of a figure. A picture of the mopeds front and a 1.80[m] high driver is 12 Mechanics shown in figure 2.3. The two figures show a vertical and horizontal calibration. The calibrations are done with a meter reference on a measuring tape. The two calibrations ensure that the two dimensions of the figure are cor- rectly calibrated. The measurements are done with an Area Tool provided by PDF X-Change Viewer.

(a) Vertical calibration (b) Horizontal calibration

Figure 2.3: The frontal areal of the moped among driver

Figure 2.3a shows that one meter on the measuring tape is equivalent to 1 5.67[m] on the photo meeter tool. Therefore a calibration of 5.67 is used for 1 2 length and 5.67 for an areal. The half-front areal on 2.3a was found to be 9.84[m2], calibrating this gives:

1 2 A = · 9.84[m2] · 2 = 0.6128[m2] (2.7) 5.67 !

Figure 2.3b shows a meter holden horizontally for calibration. One meter is equivalent to 5.1[m] photo tool measurements, therefore the calibration of 1 1 2 5.1 is used for length and 5.1 for an areal. Using the Area Tool, the half-front areal on ﬁgure 2.3b was found 8.49[m2], 2.3 Force of rolling resistance 13 and the calibrated areal is therefore:

1 2 A = · 8.49[m2] · 2 = 0.653[m2] (2.8) 5.1 !

The areal was found the be 0.6128[m2] for the vertical calibration and 0.653[m2] for the horizontal calibrations. It is therefore assumed that the areal is in the range of 0.6128[m2] to 0.653[m2], for a 1.80[m] driver. In this report the larger areal of 0.653[m2] is assumed to minimize underestimations later is the report. The drag coefficient of an object depends on how streamline the object is. Drag coefficients of motorcycles are estimated to be from 0.5 to 1.0, where Cd = 0.5 is for streamline motorbikes and Cd = 1.0 is for none- streamline bikes [39]. The Di Blasi’s moped under consideration in this report is estimated to have a drag coefficient of Cd = 0.9. After determining the air density, front areal and the drag coefficient, equation 2.6 can be written as following:

1 F = · 1.20[kg/m3] · 0.653[m2] · 0.9 · υ2 ad 2 = 0.353[kg/m] · υ2 (2.9)

2.3 Force of rolling resistance

The force acting on the moving moped caused by the tires rolling resistance µrr is called the force of rolling resistance Frr. Frr dependents on vehicles 1 total laden weight mladen and the rolling resistance:

Frr = mladen · g · µrr (2.10)

The rolling resistance depends on the road surface, tire pressure, width, diameter and construction. The resistance is caused by the deformation and slipping of the tire over the surface. At same pressure wide and narrow tires have the same contact area, however, the more narrow tires have a longer ﬂattened area S, see ﬁgure 2.4, that causes more deformation [15]. The lower rolling resistance of wider tires only accrues when the pressure is the same. Narrow tires are often capable of containing air at higher pressure,

1Laden vehicle commonly refers to loaded vehicle, in this case it is the mopeds fully fueled weight and a 70[kg] driver. The total laden weight is assumed to be 100[kg]. 14 Mechanics

(a) Contact are of wider(b) Contact are of more tire type narroe tire type

Figure 2.4: Diﬀerence of contact area shape of narrow and wide tire, from [15]

(a) Pirelli Diablo Scooter Tire (b) Michelin Reggae Scooter Tire

Figure 2.5: Tires with very diﬀerent rolling resistance, from [5] this leads to less contact area and less length of area S, thereby lowering the rolling resistance. A narrow tire has also less rotating mass, which means less force is needed to angular accelerate the tire. 2 Vehicle tires have a typical average µrr value of 0.005 upto 0.015 on concrete surface [31, 34]. The lower value of µrr is for smooth surface tires 2.5a, and the higher µrr value is for tires with tall wide gaped lugs 2.5b. Tires with tall and wide gaped lugs are designed to give better grip on soft or/and wet surfaces. The current tires on the Di Blasi moped have tall lugs and rather wide gaps,

2The rolling resistance is a function of vehicles weight and velocity, a rule of thumb gives a value of 1% increase in resistance per mph atvelocity higher than 30mph (ca. 50km/h)[19]. Here the approximated average constant is used. 2.4 Force of hill climbing 15 as shown in ﬁgure 2.6. For this reason the rolling resistance is estimated to be µrr = 0.015.

Figure 2.6: A ﬁgure of the current tire used on the Di Blasi mopeds.

For a value of µrr = 0.015 the value of rolling resistance force can be determent, using equation 2.10:

Frr = mladen · g · µrr

= mladen · g · 0.015 (2.11)

2.4 Force of hill climbing

The force of hill climbing Fhc must be added if the vehicle is not driving on a horizontal plane, but at an angle of α. The force of incline plane when driving at the angle α is described as:

Fhc = mladen · g · sin(α) (2.12)

When the slope is positive the vehicle is driving up the slope, for negative α the vehicle is driving downhill.

2.5 Force of acceleration

When the velocity of the moped is changing it is accelerating. According to Newton’s second law the acceleration of a body is equal to the vector sum 16 Mechanics of all forces acting on the body divided by the mass:

F~ ~a = (2.13) m P When considering the mopeds force of acceleration two moving parts will be addressed. First it is the force of linear acceleration Fla, describing the 3 mopeds acceleration. Secondly it is the force of angular acceleration Fωa, describing the motor’s rotor angular acceleration.

2.5.1 Force of linear acceleration

The mopeds force of linear acceleration is described by Newton’s second law:

Fla = mladen · a (2.14)

2.5.2 Force of circular acceleration

As the vehicle accelerates the motors rotor has to angular accelerate. For more accurate calculations of total force needed to accelerate the moped, the force of angular acceleration need to be added because of the rotors high angular speed. The electric motors angular acceleration is deﬁned as:

a ̟em = G · (2.15) rtire

The torque required for angular acceleration is deﬁned as:

τ = J · ̟ (2.16)

Where J is the moment of inertia. By combining equation 2.15 and 2.16, the motor torque needed for the angular acceleration is found:

Jrotor · G · a τem = (2.17) rtire

3or centripetal acceleration 2.6 The total tractive eﬀort 17

And by using equation 2.5 the force needed for the circular acceleration is found:

2 Jrotor · G · a Fωa = 2 (2.18) rtire

2.6 The total tractive eﬀort

By using equation 2.1 and insert values for the diﬀerent forces found is previous sections, the equation can be rewritten as:

τ · G kg em = υ2 · 0, 353 + m · g · µ r m laden rr tire 2 (2.19) Jrotor · G · a + mladen · g · sin(α)+ mladen · a + 2 rtyre

In the chapter 4 diﬀerent motor types are analyzed. When the motor’s data is known its torque-speed characteristics can be found. Equation 2.19 can then be used to model the mopeds accelerating characteristics. In the modeling the mopeds approximated top speed is found and the time it takes to reach the top speed. The top speed can though be controlled by a transmission pulley ratio, as seen later in chapter 3, the ration is however limited by tire size and minimum pulley size. 18 Mechanics Chapter 3

Mechanical Transmission

The mechanical power of the electric motor must be transfered to the mopeds wheel. To transfer the power a transmission is needed. Common methods to transfer power from one shaft to other are by using belt transmissions or chain transmission. The moped is currently using belt transmission. A chain in a transmission weighs more than the rubber belts, chains are more noisy and need lubrication. For those reasons, belts transmissions considered to be the optimal selection out of the two for the electric moped. In the next sections different types of belt transmissions are discussed. The effect of different gear ratio will be addressed. In the end of this chapter, the mechanical transmission currently in use on the Di Blasi bike will be evaluated and compared to other types of belt transmissions.

3.1 Belts and Pulleys

Transmission belts are often used in modern transmission systems. The belt is made of ﬂexible material, such as rubber, and are looped with great tension over pulleys to minimize slip looses. The two pulleys do not have to be in perfect line due to the belts ﬂexibility. In some applications the belt is crossed between pulleys to obtain pulley-rotations in opposite directions. Great variations of belts are available on today’s commercial marked. In this report the following four most common belt types will be addressed, in the following order: 20 Mechanical Transmission

• V-belt • Flat belt • Poly V-belt • Timing belt

V-belt, flat belt and poly V-belt transmit the power via friction between the belts and the pulleys. Therefore there will always be some loss due to slip. The belt’s slip can be minimized by increase belt’s tension and service. Timing belts use similar principle as chains, the power is transmitted by the belts teeth’s grab to the pulley. The timing belt minimize slip in the transmission system and are generally more efficient [29]. Belts run at low noise and are considered to be a low cost and high efficient solution for non-axially aligned shafts. The belts isolate noise and vibration, load fluctuations are cushioned by the flexible material, no lubrication and little maintenance is needed. The belts have though lower strength than chains and have been considered to be less tolerant to rapid high tension pulling. Because of the wide use of transmission belts, the demands are high. Today’s belts are capable of operating under higher pulling tension that formerly only allowed chains or gears. Operating temperature is for most belts around −35, 0◦C to 85◦C. The transmission belts efficiency depends e.g. on the pulley’s size, angular velocity. The losses are due to e.g. belt slippage, deformation and friction to pulley. The four types mentioned here above are different structured and are designed for different applications. Some of the designs are aimed for high accuracy, other high efficient or just endurance and strength. In the next sections the different types will be valuated and belt type thought to be best fitted to the projects applications pointed out.

3.1.1 V-belts

V-belts are the most common types of transmission belts, used in about 75% belts applications in 1997 and operate at an eﬃciency of 95-97% [29]. The V-belts are versatile and get the name by their shape. Figure 3.1 shows an example of a V-belt and a V-belt’s pulley. The shape of the belt tracks in a mating groove in the pulley, resulting in very low slip. Because of the belt’s thickness it is made fore large pulley application. As belts run over a pulley it is deformated, for small pulleys more deformation is needed, this results in lower eﬃciency. The width is usually less on the V-belt than the other three belt types and for high power requirements two ore more belts can be joined side-by-side. 3.1 Belts and Pulleys 21

(a) V-belt, from [9] (b) A V-belt pulley, from [10]

Figure 3.1: An example of a V-belt

3.1.2 Flat belts

Flat belts were used in about 15% belts applications in 1997 and operate at very high efficiency of 98% [29]. An example of a flat belt can be seen in figure 3.2, the belt is thin and wide and uses friction between the belt and the pulley to transmit the power. Because of their low thickness less deformation is needed to bend it over the pulley, making it better suited for smaller pulley applications. The belts tension needs to be high to minimize slip, the high tension increases stress on the two shatfts and bearings the pulley mounted on. The flat belt is not suited for high power applications, for higher power the belt’s tension needs to be very high to minimize the slip. The tension must though not be to high, the belt has limited allowed tension and the high tension results in stress on other components connected to the transmission system. The belts low profile results in a lower weight, specially in applications where the angular velocity of the pulley is high. At high pulley angular velocity the centrifugal force is less in the flat belt than V-belt, previously discussed.

(a) Flat Belt, from [3](b) A ﬂanged ﬂat belt pulley, from [4]

Figure 3.2: An example of a ﬂat belt 22 Mechanical Transmission

3.1.3 Poly V-belts

Poly V-belts were only, used in about 5% belts applications in 1997, the efficiency of poly V-belts is in general higher than in the other two belt types here above, or 97-99% [29]. The poly V-belt combines the advantages of V-belt and flat belt. The rippled ”V” shape of the belt, see figure 3.3, gives them about threetimes larger contact surface than flat belts, leading to less slip due to the strong grip to the pulley. The belt is flexibele and less energy is absorbed in poly V-belts than V-belts due to deformation of the belt. Theas two combined chatacteristics gives the belt it’s high efficiency. Poly V-belts are capable of transferring higher power than other belts, but is more costly solution than the e.g. V-belt.

(a) Poly V-belt, from(b) Poly V-belt ﬁtted [7] on a belt pulley, from [6]

Figure 3.3: An example of a Poly V-belt

3.1.4 Timing Belts

Timing belts (also known as synchronous belts ) where used in about 5% belts applications in 1997, the efficiency of a timing belt is very high or upto 99% [29]. What characterise the timing belt is its ripples, or tooths, that fit into a maching toothed pulley, see figure 3.4. When correct tennsioned, there is no slip losses in timing belts and they are flexible, therefore little deformation energy is abosrbed. This type of belt is capable of transmit- ting releitively large power, and is the belt that is closest to chracteristics of chains. Timing belts are often used instead of chains to minimize main- tainance, lubrication and noise. Timing belts do not relay on friction to deliver power, therefore they need the least tension of the four belts discussed here. The low tension lowers the stress on other components, such as the motors bearings. 3.1 Belts and Pulleys 23

(a) Timing Belt, from(b) Timing Belt ﬁtted [8] on a belt pulley, from [7]

Figure 3.4: An Example of a timing belt

3.1.5 Losses in belt transmissions

The losses in belt transmission systems are due to system’s velocity, frictions, aerodynamics and deformation. The first three losses are little compared to the deformation loss. The effect of deformation varies with different belt types and the larger the pulley is, the less is the belts deformation. Therefore the systems efficiency greatly depends on the pulley’s size. Figure 3.5 shows a comparison of efficiency on the four different belt types discussed above. The V-belt has the lowest efficiency due to it’s shape, the efficiency rapidly falls if the pulley’s diameter is less than 125[mm], where it has only about 94% efficiency. The timing belt has the highest efficiency and is very simular for different pulley sizes.

Figure 3.5: The efficiency of different belts at 1450[rpm]. ”Tendrem” is timing belt, ”Fladrem” is flat belt, ”Poly-V rem” is poly V-belt and ”Smalk- ilerem” is V-belt, figure from [29] 24 Mechanical Transmission

3.2 Gears ratio

The gears ratio directly affect the driving characteristics of the moped. The torque and angular velocity is manipulated through the gear difference, or gear ratio. To see how the driving characteristics of the moped are effected by the gear ratio, formulas 2.1 to 2.18 are used. The formulas, as explained in the previous section, describing the different forces working on the moped, these equations are used to plot up different values for G to see the scooters velocity over a 100[s] interval. The method will be referred to as acceleration characteristic modeling in this paper and is described in [31]. The following values are not consistent with the mopeds real values, these are only dummy values used to examen the effect of different gear ratios:

rtire = 0.21[m] kg ρ = 1.25 AIR m3 A = 0.6[m2]

Cd = 0.75 m = 185[kg]

µrr = 0.007 g = 9.8[m/s2] ◦ α = 0 dυ a = dt J = 0.097[kg · m2]

The motor used in this example is similar to a 10kW DC ’Lynch’ motor. The motors torque is assumed to be constant at 34[N] until the critical motor speed where torque begins to fall, or at the angular velocity of:

τmax = τ0 − τslope · ω (3.1a)

34[N] = 153[N] − 1.16[N · s/rad] · ωc (3.1b)

ωc = 103[rad/s] (3.1c)

Where τ0 is the motors torque at zero angular velocity, τslope is the slope of torque in relation of it’s angular velocity and ωc is the motors critical angular velocity. For ω > 103[rad/s] the torque is deﬁned as: 3.2 Gears ratio 25

G · υ τem = τ0 − τslope · (3.2a) rtire G · υ τ = 153[N] − 1.16[N · s/rad] · (3.2b) em 0.21

Now equation 2.19 can be written as: dυ 158.67 · G − 12.691 − 0.281 · υ2 103[rad/s] · 0.21 = ,for υ ≤ dt 185 + 2.24 · G2 G dυ 714 · G − 25.78 · G2 · υ − 12.691 − 0.281 · υ2 103[rad/s] · 0.21 = ,for υ > dt 185 + 2.24 · G2 G

Plotting the two equations is then done by using MATLAB, results from four diﬀerent ratio values are shown in ﬁgure 3.6. The MATLAB code used to plot the accelerating characteristics is found in Appendix A.1.

Figure 3.6: The moped’s accelerating characteristics for diﬀerent gear ratios

Figure 3.6 shows that the moped would be capable of higher speed for lower gear ratio, but on the cost of acceleration. This is due to the pulley’s size, for G = 1 the two pulley’s are the same size, resulting in same angular velocity for the tires and the motor. For G = 2 the pulley sitting on the tire shaft has double the radius of the pulley attached to motor shaft, resulting in less angular velocity but higher torque. 26 Mechanical Transmission

3.3 Current transmission system

Currently the moped uses four pulley transmission system. The primary drive uses a continuously variable transmission (CVT). The CVT uses centrifugal force to variate the pulley’s radius resulting in a gear ratio of 1.577 to 3.736. A timing belt and pulley are used for the secondary drive, with 102 gear ratio of 4.636 (or 22 )[14]. The current system setup is shown in figure 3.7, the CVT pulley is to the left in the figure. A clutch system is built in the CVT pulley, the clutches is marked with the red arrows in figure 3.7. The clutch uses centrifugal force to connect the motor shaft to the transmission system.

Figure 3.7: The transmission currently on the Di Blasi moped

Figure 3.8 shows a simpliﬁed ﬁgure of the current transmission system, where r1 is the CVT pulley with build in clutch. The two pulleys r2 and r3 are connected to the same axle, therefore rotating at the same angular velocity. The pulley marked r4 represents the pulley sitting on the same shaft as the mopeds tire, therefore r4 and the mopeds tire have the same angular velocity. The informations on the gears ratio is found on the Di Blasi’s webpage, here reprinted on section 1.3. The pulley’s with the radius r1 and r2 represent the mopeds primary drive and the pulley’s with the radius r3 and r4 represents 3.4Evaluationofthetransmissionsystem 27 the mopeds secondary drive. The primary drive’s gear ratio varies from 1.577 to 3.736 and the secondary drive has a ratio of 4.636, therefore the gear ratio from motor to wheel can be described as:

Gsys = Gprim · Gsecond (3.3a)

Gsys,min = 1.577 · 4.636 = 7.311 (3.3b)

Gsys,max = 3.736 · 4.636 = 17.320 (3.3c)

Figure 3.8: The mopeds current transmission system

The CVT’s radius is a function of its angular velocity. No informations on the relations of radius and angular velocity was found for the CVT currently used by the Di Blasi moped.

3.4 Evaluation of the transmission system

A chain and sprocket transmission system was discarded as a suitable solution due to the need of lubrication and its weight. Using a belt and a pulley transmission is thought to be better suited for the projects application. Belts are made of more ﬂexible than chains, making them more shock absorbent than chains, this gives softer take-oﬀ characteristics. Moreover, belts are cleaner, lower noise and less expensive. 28 Mechanical Transmission

Four belts where discussed here above, V-belts, flat belts, poly V-belts and timing belts. The V-belt was found to be the least efficient belt type, the flat belts are more efficient than the V-belts but put more stress on the motors bearings and is width, taking more space. The poly V-belt combines the advantages of V-belt and flat belt, however, disadvantages of the two belt types are also combined. The poly V-belt puts stress on the motors bearings and is not as efficient as the flat belt. The belt type considered to be best suited for the applications is the timing belt, that is the same belt currently used on the secondary transmission drive. The timing belt does not need to be greatly tensioned, as it does not relay on friction to transfer power, resulting in less stress on motors bearings. It has the greatest efficiency of the four belts, discussed here above, and can be used efficiently with smaller pulley’s than V-belts. The primary transmission drive uses a belt that combines V-belt and timing belt (a timing V-belt), see figure 3.7. A timing V-belt, such as this one must be used with CVT system. If a CVT system is to be used, a timing V-belt must be used. The gear ratio can be as large as G = 17 as in the current system, but by the use of four pulley system. The high gear ratio currently used with the combustion engine might not be necessary. Electric motors have key advantage over the combustion engine, electric motor provide high torque from stand still to breakpoint-rpm. This makes faster acceleration and less need for large gear ratio. The use of four pulley system and a CVT pulley is therefore considered unnecessary in the electric moped. The gear ratio of two pulley system is limited by the maximum and minimum pulley size. The minimum pulley is limited by the motor’s shaft, as it has to fit on to the shaft. The maximum pulley size is limited by the center distance of the two pulleys and the pulley’s hight from ground. The secondary gear ratio currently in use is G = 4.636, from this it is assumed that the pulley ratio can be approximately from G = 1/5 to G = 5. The final valuation of the gear ratio needs to be done after motor has been selected as it depends on the motors torque-speed characteristics. Chapter 4

DC motors

The motor is one of three very important electric components in the electric vehicle. Selecting the right types and sizes of battery, control and motor is essential. The motor has to be powerful enough to meet requirements and expectations, at the same time the motor size and weight are strictly limited. The optimal motor for this project has to be capable of providing enough power to the wheel at high efficiency, be within reasonable cost, be light and fit into the current frame. Choosing the wrong motor can lead to changes in the vehicle characteristics. If i.e. the motor is too large the moped could loose the folding ability. Therefore number of different motor types will be theoretical evaluated in the following sections. If theoretical examinations on a motor type leads to the conclusion that it might be a reasonable type for the application a physical motor of that type is found through Internet research. The Internet research is focused on finding a traction motor that is physically small but powerful enough to fulfill requirements. The evaluation and selection of motor type will be limited to DC motors. The electric power source in the foldable moped, discussed in next chapter, will be a DC power supply. By using a DC motor in combination with DC power system eliminates the need of an inverter. The first electric motor was developed through the early 1800s, beginning with Hans Øersted’s discovery of electromagnetism in 1820. In 1831 Michael Faraday building the first electric motor, Faraday’s motor was driven by DC current [13]. The DC motor has been highly developed since Faraday’s motor and today there exist number of different DC motors. Prior to 1960 30 DC motors

(a) A simple drawing of permanent (b) Commutator with seven coils magnet DC motor

Figure 4.1: Brushed DC permanent magnet electric motor, from [11]

DC motors where commonly used throughout industry and where electric motor controls where needed for varying motor speed the DC motor was generally used[26]. In the following sections the basic concept of DC motors will be covered as their main components. Introduction on diﬀerent types of DC motors and their applications will thereafter be introduced. One of the projects goals is to make a MATLAB simulation of the electric moped. The simulation gives valuable informations on the mopeds expected range and speed. In order to do these simulations a rather detailed discussion on motor behavior and characteristics are thought to be essential. Therefore will the following sections have detailed discussion on motor behavior and characteristics. The current combustion motor has a maximum torque of 2.56[Nm] and a maximum power of 0.86[kW ]. The aim is to focus on electric motors that are capable of delivering similar, but no less torque and power.

4.1 Brushed DC permanent magnet electric motor

The brushed DC motor is fairly simple to describe and understand, it is widely used and has a history of being used as a traction motor [31]. The brushed permanent magnet DC electric motor is considered to be a good starting point because characteristics of other motor types discussed later can be more easily explained by referring to the brushed DC electric motor. The following sections will cover other common types of DC electric motors, such as brushless and wounded field DC motors. Figure 4.1a shows a simplified image of DC motor, the motor is equipped with brushes and permanent magnets. For simplification the motor is only 4.1 Brushed DC permanent magnet electric motor 31 shown with armature of one wire coil, in a practical motor there are more than one wire coils in an armature. Each wire coil is connected to a pair of commutators, sitting on the armatures shaft. An example of 7 coil armature is shown in figure 4.1b, the commutator is deviated up to 14 electrically isolated connection parts, two for each coil. The commutators, with help of brushes, deliver electric current to the coils. Because of the 14 electrical isolated parts of the commutator, the current switches direction within the coils as the commutator rotates. The direction of the current is therefore always the same in the wire close to the south pole, and wise versa. To realize the magnetic force rotating the motors armature, simplified DC motor on figure 4.1a is used. The armature has a low resistance Ra and when the motor is applied voltage source Es, high current starts to flow in the armature. The force of the magnetic field formed by the current running in the coil wire, and the magnetic force from the permanent magnets form the rotational force. Current running from the commutator gives a downwards force and current running towards the commutator gives upwards force, see figure 4.2. These forces add up to produce a powerful torque. To change the rotating directions, current directions are changed. When the armature has rotated 90◦ the half rings of the commutator change the current direction of the coil and maintain the same rotational force direction.

Figure 4.2: The magnetic force rotating the armature. The ”X” marks the current direction from the reader and • marks the direction towards the reader, from [35].

To maximize the motors performance the wire coil is wound round a iron core to minimize the air gap the magnetic ﬁeld crosses. More than one coil and pair of magnets are used to optimally exploit the magnetic rotational force. For increasing the torque, the number wire windings is increased in each coil. 32 DC motors

4.1.1 Torque

If a current carrying conductor is placed in a magnetic field, it is subjective to a electromagnetic force, Lorentz force [22, 40]. The magnitude of the force depends on the conductors length and its orientation with respect to the direction of the magnetic field. The force is zero when the conductor is parallel to the magnetic field and when conductor is perpendicular to the magnetic field the force is greatest. The maximum force acting on a perpendicular conductor Fcon can be describes as:

Fcon = B · ℓcon · Icon (4.1) where B is the flux density of the magnetic field, ℓcon is the conductors length in the active magnetic field and Icon is the conductors current. A motor with a coil radius of rcoil and wire turns of nturn, the torque is described as:

τem = 2 · nturn · rcoil · B · ℓcon · Icon (4.2)

The total ﬂux passing through the coil is described as φ = 2 · rcoil · B · ℓcon, implementing this into equation 4.2 gives:

τem = φ · nturn · Icon (4.3)

Equation 4.3 is only valid for the peak torque when the conductor is perfectly perpendicular to the magnetic ﬁeld of one pole pair. This is not the case in practical motors, for this reason motor constant Km is used. The motor constant is used to describe the average torque with relation to the conductors current and the magnets magnetic ﬂux. It depends on the number of wire turns in each coil, number of pole pairs and other physical factors. For a known value of Km, the motors torque is given as:

τem = Km · φ · Icon (4.4)

Motor manufactures sometime give information on Kmφ, often called torque constant. From equation 4.4 it can be seen that the motors torque is controlled by the intensity of the magnetic ﬂux φ and the coils current, where the current is aﬀected by the armature’s coils resistance Ra and the suppled voltage source Es.

As the armature rotates in the magnetic ﬁeld a voltage Eb is induced in each coil conductor, as happens when the machine is used as a generator. This applied voltage is often referred to as back EMF (electromotive force). If 4.1 Brushed DC permanent magnet electric motor 33 considering the setup as in ﬁgure 4.1a, according to [40] the back EMF can be given as:

Eb = B · ℓcon · υcon (4.5)

where υcon is the velocity of the moving conductor through the magnetic ﬁeld. The conductors form loops of nturn coils and sit on the cylindrically shaped armature. Equation 4.5 can therefore be rewritten as:

Eb = 2 · nturn · B · ℓcon · rcoil · ωa (4.6)

where the ωa is the armature angular velocity. As for equation 4.2 this is only valid for the simpliﬁed motor setup as shown in ﬁgure 4.1a. For a practical motor application the motor constant Km can be introduced to describe the motors characteristics, regarding the physical setup. By taking similar step as from equation 4.2 to equation 4.4 by inserting Km·φ = 2·nturn·B·ℓcon·rcoil equation 4.6 can be written as:

Eb = Km · φ · ωa (4.7)

The net voltage across the armature is the voltage diﬀerence of the supplied voltage and the back EMF, Es −Eb. As describe in equation 4.4, the motors torque is aﬀected by the coils current. Furthermore, by implementing equation 4.7 the coils current is found as a function of the armaturea angular velocity:

Es − Eb Es Km · φ Icon = = − · ωa (4.8) Ra Ra Ra and now by implementing equation 4.4 the following is obtained:

2 Km · φ · Es (Km · φ) τem = − · ωa (4.9) Ra Ra

According to [40] the mechanical power output of a motor depends upon its rotational speed and the torque it develops, the power is thus given as:

Pmotor = ωa · τem (4.10) 34 DC motors

Seen by equation 4.9 the motors torque is at it’s maximum when the armature is standstill, or when stalled. The delivered torque falls as the armature gains angular velocity, the relation is linear as shown in figure 4.3. Equation 4.9 and figure 4.3 give a theoretical description of a DC motor torque-speed characteristics. Usually the torque at low speed is limited by the motor controller. To obtain the high torque, high current must be fed to the motor. Motors have limited current capability, too high current can overheat and damage the motor. Motors are rated with nominal current, or maximum continuous current rating. The motor is capable of handling higher current than rated nominal current for a short time, but for longer running time at high current the risk of overheating the motor is great. Motors data sheets often provide thermal data, the limits of current-time can be found using these data, if high torque is needed for a short time. It should be noted that the power plotted in figure 4.3 does not have the same y-ax values as the torque, this is only to show the relations of power and torque at different angular velocity.

Figure 4.3: A theoretical description of a DC motor torque-speed characteristics.

4.1.2 Controls

It is essential that the motor power can be controlled by the driver. The mechanical power delivered by the motor is a function of the motors torque and its angular velocity, as can be seen in equation 4.10. The motors torque 4.1 Brushed DC permanent magnet electric motor 35 might be required to be low or high when accelerating from standstill, depending on driver and situation. If vehicle is to accelerate from standstill on a slippery surface the required motor torque might be much lower than the motor torque required in optimal driving situation. The power control of a brushed DC permanent magnet electric motor is done by varying the supply voltage to the motor. Let us consider the situation in figure 4.3 and assume it represents the torque-speed characteristics for the motor’s maximum voltage. By lowering the supply voltage the stall torque is lowered. The second half of equation 4.9 is still unchanged, therefore the slope and the motors linear characteristics are unchanged. This means, if the supply voltage can be varied from Es = 0[V ] to motors maximum voltage. The motor can operate at any torque/speed below the maximum values, plotted as red in figure 4.3. More details on different control system types and design is not considered in this paper. Analysis on different motor control designs can be reviewed as further works of this paper.

4.1.3 Eﬃciency

Efficiency is important for all components within the electric vehicle. The vehicle range greatly dependent on its overall system efficiency. The vehicle’s overall efficiency is from the battery charger to the vehicles tires road resistance. The electric motor is one of the components effecting the overall efficiency, selecting a motor that operates at efficient level must therefore be addressed. Electric power is the input to an electric motor and mechanical power is the desired output. This energy conversion involves though some heat energy to be generated. The heat generated is no use to the system and is referred to as motor losses. The motor losses can be deviated into mechanical and electrical losses. The topic of this section is focused on the losses in brushed DC machines, the major sources of losses are though the same for all electric motors. Mechanical losses are due to the moving parts of the motor and are caused by the bearings friction, brush friction and windage. The losses due to friction depend on the motors speed and design, rather than motor type. The majority of the windage loss is due to the motors cooling system. Usually a fan is mounted internally on the motors shaft, when the fan is rotating a windage loss is obtained. The windage loss is dependent on the motors speed and the fans design, rather than motor type. Some motor designers provide other cooling solutions, such as liquid cooling. According to [31] the 36 DC motors

power associated with the mechanical friction loss Pfr and the windage loss Pwp can be described as:

Pfr = τf · ωa (4.11a) 3 Pwp = kwp · ωa (4.11b) where τf is the torque due to friction and kwp is a constant depending mainly on the size and shape of the rotor and whether a cooling fan is ﬁtted. Seen in equation 4.11b the windage loss greatly depends on the armatures angular velocity. Electrical losses are due to the electric components in the motor and can be deviated into conduction losses and iron losses. Conductor losses, often called copper losses, are losses due to electric current in the motors conductors. In the conductors some of the electrical energy is converted into heat energy instead of electrical work. This loss depends on the motors current and the conductors resistivity, length, cross section and temperature. The heating eﬀect of an electrical current can be use to describe the conductor losses Pcl:

2 ℓcon Pcl = Icon · ρ0 (1 + αtemp · Tcon) · (4.12) Acon where ◦ ρ0 = the conductors resistivity at 0 C [Ω · m] ◦ αtemp = the temperature coeﬃcient [1/ C] ◦ Tcon = the conductors temperature [ C] 2 Acon = the conductors cross section [m ]

Equation 4.12 shows that the conductor losses increase with increased conductor temperature, or motor temperature. A motor that has been running for several minutes has a rather stable conductor resistance. For simpliﬁ- cation the conductor temperature diﬀerence is neglected and the conductor resistance Rcon is assumed to be constant. The conductor losses are now set as a function of the torque provided by the motor using equation 4.4:

2 Pcl = kc · τem (4.14) where Rcon kc = (Km · φ) 4.1 Brushed DC permanent magnet electric motor 37

(a) Armature solid core (b) Armature core made of ﬁve layers

Figure 4.4: Eddy current in a solid and layered armature, from [30]

The conductor losses are the largest cause of inefficiency and occur in the armature, commutating poles, brushes and for field wound motors it occurs also in the shunt field, series field and compensating windings. Iron losses are due to hysteresis and eddy currents, the iron losses are caused by the magnetic effect in the iron of the motor, mainly in the armature. Iron losses depend upon the motors angular velocity, the magnetic flux density, the size of the armature and the quality of the steel used in the motor design. As the armature rotates its windings are affected by the constantly changing, north to south, magnetic field of the permanent magnets. Though the magnetic fields of the permanent magnetics are constant the magnetic field seen by one piece of iron in the turning armature is oscillating and therefore constantly changing. This oscillating magnetic field intensity is the cause of two different losses. One of the two losses is the hysteresis loss. The hysteresis loss is caused by the energy required to magnetize and demagnetize the constantly turning armature iron core. In a properly designed motor a good magnetically soft iron should be used that reduces the hysteresis loss. Usually the hysteresis loss is very low, but are never zero. The second iron loss discussed in this paper is the loss caused by eddy currents. The armatures core is made of metallic material and when rotating in a magnetic field, eddy currents occurs. The outer portion of the cylindrical metal core cuts more line of magnetic force than the inner. This causes voltage potential within the armatures metallic core that leads to eddy currents. Eddy currents tent to consume a considerable amount of energy that results in temperature rising in the armatures core. One way of reducing the eddy currents is to split up the core in a multiply thin electrical isolated layers. The voltage induced in each layer is 1 · V , where n is the number of nlay core lay layers in the core and Vcore is the voltage potential in a solid core. By this method the losses are considerably reduced. 38 DC motors

The iron losses are proportional to the frequency of changing magnetic ﬁeld and the rate of changing magnetic ﬁeld is proportional to armatures angular velocity. According to [31], the iron loss Pil is therefore described as:

Pil = ki · ωa (4.16) where ki is a constant if magnetic field is assumed to be constant. Total efficiency is the ratio between the useful output power and the total input power. The total input power can also be described as the total power loss added to the useful output power, by that the motors efficiency ηm can be found as:

Pout ηm = (4.17a) Pin P = out (4.17b) Pout + Ploss τem ωa = 3 2 (4.17c) τem ωa + τf ωa + kwp ωa + kc τem + ki ωa

Using similar method as described in [31], the efficiency can be plotted as a function of the motors output torque and its angular velocity. The results are shown in figure 4.5, a plot of this type is often known as motors efficiency map. The MATLAB code and constants values for the plot are found in Appendix A.2. The efficiency map is to show how the efficiency is dependent on the motors output torque and the armatures angular velocity. It can be clearly seen from the example efficiency map here above that the efficiency is not highest when the torque or speed of the motor is highest. Selecting wrong size can lead to nominal motor efficiency of under 70%, though the motor is rated much higher. In the following it will be explained how different motor types have different efficiencies. It is therefore considered to be essential to select both the best suited motor type and motor size, for the system efficiency to be high.

4.1.4 Regenerative braking

When reducing the vehicles velocity the electric motor can be used to capture the energy otherwise converted to heat when using hydraulic brakes. The energy captures can be stored in the vehicles electrical energy storage system. This method is called regenerative braking and has great potential in gaining vehicle range. 4.1 Brushed DC permanent magnet electric motor 39

0.85 35

0.8 30

0.75 25

0.7 20 Torque/Nm 0.65 15

0.6 10

0.55 5

0.5 50 100 150 200 250 300 350 400 450 500 Speed/rad.s−1

Figure 4.5: An example of eﬃciency map of a typical brushed DC permanent magnet electric motor

Considering the situation where the motor is disconnected from its power source and acts like a generator, running at ωa and delivering a torque of 1 τem, connected to a battery . The same theory as in equation 4.8 is used to deﬁne the current generated by the motor:

Km φ ωa − Vb Ieg = (4.18) Ra where

Ieg = the electric generators current [A]

Vb = the battery voltage [V ]

Km φ ωa = the voltage generated by the motor [V ]

The negative torque produced to slow down the vehicle is proportional to the current Ieg found above:

1The motors energy source and the battery used for regenerative braking system can possibly be the same energy storage unit. 40 DC motors

τeg = Km φ Ieg (4.20a) (K φ)2 ω − K φ V = m a m b (4.20b) Ra

As the armature angular velocity is reduced, the voltage potential is reduced. At high velocity the generators voltage might be higher than the battery voltage, making the current direction towards the battery and therefore charging it. However, for a low angular velocity the generators voltage will be lower than the battery voltage. If Km φ ωa < Vb, the current direction will be from the battery to the motor and no braking effect occurs. For this reason a DC/DC converter is essential for an effective regenerative braking system. A figure of a regenerative braking system with a DC/DC converter can be seen in figure 4.6. The DC/DC converter draws current from the motor Im at a voltage Vm. The input voltage to the converter depends on the generators speed, as before. The current drawn from the generator is controlled by the mopeds driver to produce the desired braking torque. The DC/DC converter has a stable output voltage that meets the electrical energy storage system’s recharge mode specifications. The converters output current varies with generators speed. The power delivered by the converter is defined as:

Pcon out = Pcon in · ηcon (4.21) where ηcon is the DC/DC converters eﬃciency. With the use of DC/DC converter it is possible to recharge the battery by regenerative braking at any generator speed, though the energy at low speed is little. More importantly, the regenerative braking system can be used over wider range of vehicle speed.

Figure 4.6: Regenerative braking system with a DC/DC converter, from [31]

Studies on regenerative braking system has been done by Peter Clarke, Tariq Muneer and Kevin Cullinane [23]. The EVT 4000E electric motor scooter 4.1 Brushed DC permanent magnet electric motor 41 with fitted regenerative braking system and ultracapacitor energy storage was used for simulating the effect on energy efficiency. The regenerative braking system fitted was found to have an overall efficiency of 60% and weighing 1 kg. The scooter trails where only conducted for city driving mode. The results from Peter Clarke, Tariq Muneer and Kevin Cullinane simulation is here reprinted in figure 4.7 and show an increas in range per charge of 18.1%.

Figure 4.7: Increase in fuel eﬃciency of EVT scooter with varying size of ultracapacitor energy storage. Note: this is useful energy storage, not ultracapacitor maximum energy storage. Also, the motor/generator is rated at 1.5 kW as supplied by manufacturer. Figure from [23]

Dual braking system is often used to maximize the braking, this has been done successfully by Vectrix Corp. on their VX-1 electric motorbike. The throttle is turned counterclockwise for regenerative braking and hand-brakes are ﬁtted for friction braking system. The throttle is shown in ﬁgure 4.8

4.1.5 LEM-130

LEM-130 motor is a Lynch type of brushed DC permanent magnet electric motor manufactured by Lynch Motor Company Ltd. The Lynch motor was invented by Cedric Lynch and developed by Cedric Lynch and Trevor Lees in the early 1990s. The motor was designed to be more eﬃcient than other DC motors and developed for use in light electric vehicles. Figure 4.9 shows the motors data. By implementing the speed constant and armature resistance, found in the motor data, into equations 4.7 and 4.9 the motor torque-speed characteristics can be found. This yealsd: 42 DC motors

Figure 4.8: Dual braking system used on the VX-1 electric motorbike, from [16]

Figure 4.9: LEM-130 motor from Lynch Motor Company Ltd. approx weight 3kg

1[V ] 60[s] 138[rpm]= · (4.22a) Km φ 2π =⇒ Km φ = 0.0692[Nm/A] (4.22b)

60[s] because the speed constant is given in [rpm], 2π is used to convert from [rpm] to [rad/s]. The torque constant found by this method is very close to the value given in the motor data. The values of torque constant Kmφ, voltage source Es = 48[V ] and armature resistance Ra = 32.5[mΩ] is now implementing to equation 4.9:

Nm Nm 2 0.0692 A · 48[V ] 0.0692 A τem = − · ωa (4.23a) 32.5[mΩ] 32.5[mΩ] = 102.2 − 0.147 ωa (4.23b) this describes the motor’s torque characteristics at variable speed. For continuous operation, the motor is capable of handling limited current. The peak current given in the motor data is the motors maximum continuous 4.1 Brushed DC permanent magnet electric motor 43 current rating current. The LEM-130 motor is rated 4[kW ], or over four times more powerful than the current combustion engine. In these torque- speed calculations the current will be set to the value of rated current 75[A]2. Using equation 4.4 and the maximum continuous current the motor, maximum torque can be found:

τem max = 0.0692[Nm/A] · 75[A] = 5.2[Nm] (4.24)

Now the motors torque-speed characteristics can be plotted and are here shown in ﬁgure 4.10. The critical motor speed ωc is where the torque starts to fall, ωc is found by inserting τem max into equation 4.23b and solve for ωa. This gives a critical motor speed of ωc = 659.9[rad/s].

Figure 4.10: LEM-130 motors torque-speed characteristics

4.1.5.1 Modeling the LEM-130

Modeling the moped using the LEM-130 motors characteristics can give valuable information on the acceleration characteristics, the modeling is done

2The motor can operate safely at higher current, 100[A], this should result in higher torque. 44 DC motors by using equation 2.19 and the following values:

τem = 5.2[N] , for ωa ≤ ωc G τem = 102.2 − 0.147 υ , for ωa >ωc rtire G = {5, 6, 7, 8}

rtire = 0.155[m], the mopeds tire radius.

mladen = 100[kg], the mopeds current weight plus 70[kg] driver. g = 9.8[m/s2] ◦ α = 0 , flat road is assumed. J = 0.0117[kg m2] dυ a = , acceleration is defined as differentiation of velocity. dt

The timing belt was considered to be best ﬁtted to the applications, therefore the transmission systems eﬃciency is assumed to be 99%. With the following values equation 2.19 can be rewritten as:

kg dυ 33.21[N]G = 14.7[N] + 0.353 υ2 + (100[kg] + 0.49[kg]G) (4.26a) m dt dυ 33.21[N] · G − 14.7[N] − 0.353[kg/m] · υ2 =⇒ = (4.26b) dt 100[kg] + 0.49[kg] · G

Equation 4.26 applies until the critical angular velocity where the torque begins to fall, or for ωa ≤ ωc. For ωa > ωc the torque is deﬁned by equation 4.23b and the following equation applies for the vehicles acceleration characteristics:

dυ 652.76[N]G − 6.06[kg/s]G2υ − 14.7[N] − 0.353[kg/m] · υ2 = (4.27) dt 100[kg] + 0.49[kg]G

Using the same method as in section 3.2 but with the output values from the equations 4.26b and 4.27 the moped’s full power acceleration is plotted, MATLAB code used for modelling tha acceleration is shown in Appendix A.1. As can be seen in figure 4.11, there is a trade of between the acceleration and the maximum vehicle speed. Different values of gear ratio where exper- imentally set to find the maximum speed the motor could deliver. The gear 4.1 Brushed DC permanent magnet electric motor 45

Figure 4.11: The moped’s acceleration characteristics using LEM-130 motor ratio G = 5 was found to give the most speed. When the gear ratio is set to G = 5 the maximum vehicle speed is 73.55[km/h], it takes however about 45[s] to reach that speed. When setting the gear ratio to G = 6 the moped reaches it’s maximum speed of 62.33[m/s] on 17[s]. The gear ratio of G = 5 reaches 62[m/s] in approximately 21[s], not a considerably difference. Gear ratio of G = 5 is therefore considerer to be optimal for the motor LEM-130 from Lynch Motor Company Ltd. The LEM-130 motor is a high speed motor, capable of operating at high RPM, for this reason the gear ratio must be high. A gear ratio of appr. 5 was considered to be the higher limit of gear ratio, due to tires axel hight from ground. Motors with rated less RPM will be considered in the following sections. The motor was digitally fitted into the frame by photo manipulation. The results showed that the motor can be easily fitted into the mopeds current frame. Images of the photo manipulation is in appendix D.1.

4.1.6 PMG 132

Modeling of the PMG 132 Lynch motor from PERM MOTOR GMBH, was also done. The PMG 132 motor is rated 2.5[kW ], less power than the LEM- 46 DC motors

130 motor. The PMG 132 motor is capable of delivering high torque, and should therefore have high acceleration. Figure 4.12 shows the motors data and the results of the modeling, where the following results where obtained for diﬀerent gear ratios:

for G = 0.5, υmax = 62.6[km/h]

for G = 1.0, υmax = 59.6[km/h]

for G = 1.5, υmax = 41.2[km/h]

for G = 2.0, υmax = 31.2[km/h]

The moped is capable of reaching 62.6[km/h] when using the PMG 132 motor and a gear ratio of G = 0.5, reaching the top speed takes though about 50[s]. Setting the gear ratio to G = 1 does lower the maximum speed, or down to 59.6[km/h], the time it takes the motor to reach the top speed is less than for gear ratio of G = 0.5, or approximately 12[s]. It is therefore considered to be optimal to set the the gear ratio to G = 1 when using the PMG 132 motor.

Figure 4.12: The moped’s acceleration characteristics using PMG 132 motor

Further information on the PMG 132 motor’s mechanical drawing and motor’s characteristic curves are provided in appendix B. Similar photograph manipulations where done to see if the motor fitted into the frame. After scaling the motor drawing and fit it into a photo of the mopeds side, it was clear that the motor did not fit into the moped’s frame. When moped is folded the motor would collide with the tire of 4.2WoundfieldDCelectricmotors 47 the moped. The manipulated photograph is shown in Appendix D.2, the red area represents the area where the mopeds tire would collide with the motor. There is a large weight difference of the two motors, LEM-130 weighing 3.0[kg] and the PMG 132 motor weighing 11.0[kg] and is physically too large for the application as it does not fit into the frame. The total weight of the vehicle affects its driving range performance, it is therefore essential to minimize the weight. The two motors modeled here above are considered to be high efficient, low weight (LEM-130) but high cost solution. AMG DC permanent magnet motors from Iskra Avtoelektrika come at a lower price, and have a reasonable weight of 5.7[kg]. Not enough technical information where available at this time to perform acceleration characteristics modeling on the AMG motor from Iskra, the available technical informations are provided in appendix B.

4.2 Wound ﬁeld DC electric motors

Wound field DC electric motors are similar to the permanent magnet electric motor, the main difference is that coils are used rather than permanent magnets to provide motors magnetic field. The coils are placed in the motor’s stator, similarly where the permanent magnets are placed in a permanent magnet motor. As current passes through the wire coil, a magnetic field is produced. The magnetic field produced is direct proportional to the current in the coil wires. This makes it possible to control the motor by varying the magnetic field strength. Wire wounded coils are also less expensive than permanent magnets, lowering the price of the motor. The field windings need electric current to produce the magnetic field, as current passes through the field windings I2R losses occur where heat is produced. Wounded filed winging motors are though not damned to have less efficiency than permanent magnetic motors. Good motor control system can optimize the wound field motor’s performance and minimize the losses, making it even more efficient than the permanent magnetic motor.

The motor characteristic value ki introduced in equation 4.16 was assumed to be constant for permanent magnetic motors. This is not true for field winding motors as the magnetic field is constantly altering. By proper design the value of the ki factor can be reduced, leading to lower iron loss in the motor thereby more efficiency. The wound field motor has a wide torque-speed operating range. Assuming the stator’s coils current is constant, giving a fixed magnetic flux. The motor’s torque-speed characteristics are similar to the characteristics of a 48 DC motors

(a) Varying the commutators voltage at con-(b) Varying the magnetic ﬂux at constant stant magnetic ﬂux commutators voltage

Figure 4.13: Wound field motor’s torque-speed characteristics permanent magnet motor. The slope of the function is the same, where the motor can be controlled by varying the commutators voltage. If a constant commutators voltage is now assumed, the varying magnetic flux is used to control the motor. For lower magnetic flux, the slope of torque-speed relations becomes flatter. To realize the motors behavior when varying the commutators current and/or varying the stator’s magnetic flux equation 4.9 is used to plot up the difference. Figure 4.13a shows the operating range of constant magnetic flux, the motor is capable of operating anywhere within the area limited by the motors maximum voltage. The difference of high and low stator’s magnetic flux is shown in figure 4.13b. By lowering the magnetic flux the motor is capable of operating at wider angular velocity range but at lower torque. More than one wound field DC electric motor type is available. The difference is mainly due to the setup of the physical components, that furthermore, results in different motor characteristics. Here three different wound field DC motors will be discussed.

4.2.1 Series

In the series motor the field windings are connected in series with the armature. The series motor is capable of developing great torque at stand still and low speed. The torque varies with the square of the current, for high torque motors the field windings are thick and few. At startup there is no magnetic field and therefore no back EMF that limits the current flow to 4.2WoundfieldDCelectricmotors 49

Figure 4.14: Series connected wound field DC electric motor the armature. This can result in a start torque of much greater than rated motor torque, the current is though limited leading to a maximum torque. As with the permanent magnet motor, the series motor reaches a critical speed where the motors torque starts to rapidly fall. The series motor is appealing for EV application because of the high start torque, or stall torque. This makes the motor capable of high acceleration from standstill. As the motor accelerates the armature’s current and thereby the back EMF decreases. This makes the motor capable of very high RPM and with no load connected, motors RPM might have to be limited. At high speed the torque becomes less, resulting in slow speed when driving steep hill climbing. By reversing the current flow in the series motor the turning direction will not change. The field windings are series connected, that is, the same current flows through the field windings as flows through the armature. To reverse the rotational direction, the direction of the field windings current flow must be changed with perspective to the armature current. It is therefore not practical to use series connected motor where counterclockwise rotation is needed. The series motor speed can be adjusted by the use of resistors. For increasing the speed a small resistor can be placed in parallel with the series field. This leads to current reduction in the field windings and thereby lowering the field windings magnetic flux. To lower the speed a resistor is series connected to the field windings and armature. This results in small voltage drop over the resistor and thereby reducing the armature’s supply voltage [40]. A typical torque-speed and torque-current characteristics of a series motor are shown in figure 4.15. The torque is only plotted for motor’s angular velocity of ωa > ωc, for ωa < ωc the torque is constant due to current limiting. Earlier attempts of using series motors in regenerative breaking systems show an instability behavior in the system[33]. Regenerative breaking sys- 50 DC motors

Figure 4.15: A typical torque-speed and torque-current characteristics of a series motor, from [40]

tem using series motors need advantage motor control system to maintain the stability of the system. This is well doable with modern power electronic systems, but might come to and extra cost. Series DC motors prove to be popular among amateur EV builders, the webpage [2] is a collection of 2979 EV amateur projects. Out of the 2979 vehicles, 1383 are currently listed to have series motor installed, correspond- ing to 46.4%. The motors used in those projects are, in almost all cases, larger than needed for this project. WarP motors from NetGain Motors, Inc. are series DC commercially available motors. The WarP motors are one of the motors found popular among amateur EV builders. NetGain designed the motors to be used in larger vehicles than considered in this project. Advanced Motors Inc. is a company that specializes in custom engineered solutions, the company also provides a small product line of series DC motors [1], no technical information about their motor have been found through In- ternet research. An e-mail was sent to a Advanced Motors Inc. sale contact and costumer service, these e-mails are found in Appendix D. Mechanical drawings and measurements results from motor tests on two motor types, 140-07 and A00-4009, where provided by the e-mail contact, found in Ap- pendix B. 4.2WoundﬁeldDCelectricmotors 51

4.2.1.1 140-07

Motor type 140-07 from Advanced Motors Inc. has the following ratings from 37.5[V ] performance test, read from chart found in B.4.1:

140-07 from Advanced Motors Inc. Continuous 1 hour P 1.32[kW ] (1.8[HP ]) 1.62[kW ] (2.2[HP ]) ω 4600[rpm] 4000[rpm] τ 2.7[Nm] 4.2[Nm] η 72.5% 75% I 50[A] 62[A]

The rating in the table above are now used to estimates how fast the moped would be capable of driving using the 140-07 motor from Advanced Motors Inc. The mopeds top speed is limited by three factors, motor maximum torque, motor maximum speed and gear ratio. The motor torque and speed is given in table above, plotting up the mopeds velocity for diﬀerent gear ratios with perspective to motor torque and motor speed gives valuable information on mopeds top speed capabilities. As the moped reaches top speed the acceleration becomes approximately zero. Therefore equation 2.19 can be expressed as, assuming ﬂat driving surface:

τ · G kg em = υ2 · 0, 353 + m · g · 0, 015 (4.29) r m Solving for gear ratio G gives:

0.353υ2 + m · g · 0.015 r G = (4.30) τem And now deﬁning the mopeds velocity for diﬀerent gear ratios with perspective motor speed:

2ωπr G = (4.31) υ · 60[s]

The motor speed is not constant, this estimation is used to give a quick and rough estimation on the mopeds speed capabilities at diﬀerent gear ratios. Through several comparisons, this method proved to give a reasonable estimation on gear ratio and top speed. 52 DC motors

(a) Results using data from continuous rat- (b) Results using data from 1 hour rating ing

Figure 4.16: Modeling the mopeds top speed at diﬀerent gear ratios using the 140-07 motor from Advanced Motors Inc.

Inserting values from mopeds specifications and 140-07 motors characteristic table above into equations 4.30 and 4.31, gives the following results shown in figure 4.16. The moped is estimated to be capable of reaching the maximum speed of 14.55[m/s] (or 52.38[km/h]), for both constant and 1 hour ratings, using the 140-07 motor from Advanced Motors Inc. Top speeds for integer values of gear ratio is also shown in figure 4.16. In theory the series motor should be capable of higher torque at low speed than the brushed permanent magnet motor, resulting in greater acceleration from standstill. After measuring the width of the foldable frame, it was discovered that the 140-07 motor does not fit into the frame. Figure F.1 in Appendix F shows the width of the moped’s folding mechanism. The motor’s total width must be less than 230[mm] to fit into the current frame. The 140-07 motor’s width is 263.02[mm], see Appendix B.4.1 for motor drawings.

4.2.2 Shunt

The shunt DC motor is similar in construction to a series motor. The difference is the parallel, instead of series, connections of the field windings to the armature. The motors field windings consist of thin wire, because of the thin wire more turns are capable. As with the series motor, the field wind- 4.2WoundfieldDCelectricmotors 53

Figure 4.17: Parallel connected wound field DC electric motor ings magnetic field is proportional with the field windings current, but the shunt motors thin wound field wire cannot handle high current. According to equation 4.3, the field windings magnetic flux is not only bound to the windings current, but also the number of turns. That is why the low current of shunt motors field windings are capable of providing high magnetic flux through number of turns. However, the low field coil current results in low starting torque. The shunt motor is preferred where constant motor speed is needed. The armatures critical angular velocity is often very close to the motors maximum angular velocity. The torque drops very steeply for angular velocity above critical point, as can be seen in figure 4.18. As the shunt motor reaches full speed, the armature produces high back EMF. If motor load is increased, slowing the motors down, less back EMF is produced which will cause more current to flow. The gain in current provides more torque and the motor will slowly regain full speed. The motor speed of a shunt motor stays therefore relatively constant from no load to full lead, the variation is normally around 10-15% [40]. The shunt DC motor’s speed can be varied by controlling the current supplied to the shut field. This control has though limited effect and allows only 10-20% variation on the motors full rpm. Another method is to control the current supplied to the armature by lowering the motors supply voltage. The shunt DC motor tends to overheat when operating below full voltage, therefore cooling is thought to be essential [39]. As for the series motor, reversing the current flow will not result in changing rotational direction. The field windings are parallel connected, that is, the same current direction flows through the field windings as flows through the armature. To reverse the rotational direction, the direction of the field windings current flow must be changed with perspective to the armature current. As for the series motor, it is not considered practical to use shunt DC motors where counterclockwise rotation is needed. 54 DC motors

Figure 4.18: A typical torque-speed and torque-current characteristics of a shunt motor, from [40]

Because of the low starting torque, the shunt motor is expected to have a low acceleration from stand-still. Using shunt motors in vehicle applications might need lower gear ratio to gain acceptable acceleration from stand-still. The shunt DC motor is also particularly diﬃcult to control, where speed variation is limited. Therefore the shunt motor is excluded as a suitable motor type for the this project.

4.2.3 Separately excited

Figure 4.19: The separately excited DC motor has independent input terminals for the wound ﬁeld and the armature

The separately excited DC motor is capable of operating at greater range than shunt and series motors. The motors field windings and the armatures coils are not internally connected, allowing separately controlling. By separately controlling the voltage applied to the field windings and voltage 4.3 Brushless DC permanent magnet electric motor 55 applied to commutator the motor can take full advantage of the torque-speed characteristics diagram shown in figures 4.13a and 4.13b. If a high torque is required at standstill or low speed, the voltage applied to the field windings is set high. This increases the current in the field windings and thereby the motors magnetic flux. The high magnetic flux emitted by the field windings limit the motor speed. By lowering the voltage applied to the field windings, weakening the magnetic flux, higher motor speed is resulted. The motor speed of the separately excited DC motor can also be controlled at greater range. To lower the motor speed at a given motor flux, the commutators voltage is lowered. The motor control for separately excited DC motor is somewhat more complex than the motor controllers for the motors discussed here above. The results of modeling the permanent magnet motor showed that the permanent magnet motor is capable of sufficient acceleration from standstill. Further- more, the mopeds top speed was above the required speed of the project when modeling the LEM-130 motor. The series motor is capable of even greater torque at low speed than the brushed permanent magnet motor, resulting in greater acceleration considering similar motor size. It is fore those reasons the wide operation range that characterize the separately excited motor is not essential for the projects application. It is therefore concluded that the separately excited DC motor is not considered to be the optimal solution for this project.

4.3 Brushless DC permanent magnet electric motor

A brushless DC motor (BLDC) is a permanent magnet excited synchronous motor, driven by an inverter triggered in accordance with the rotors position [28]. The BLDC is somewhat similar build as the brushed DC permanent magnet electric motor described in section 4.1. Instead of having the wire field coils in the rotating part of the motor and the permanent magnets in the stator, the field coils are placed in the motors stator and the magnets in the rotor. No is therefore need to be applied to the permanent magnet, therefore no current is needed to be transfered to the only rotating part of the motor. This simplifies the motors construction as there is no need for brushes or commutator, the weight of BLDC motors can therefore often be less than of brushed DC motors. The commutator is though very important in the brushed DC motor, it is an essential component in the motor control system. By not having a com- 56 DC motors

(a) Figure from www.renesas.eu (b) Figure from http://dev.emcelettronica.com

Figure 4.20: The construction of the BLDC motor. mutator, more complex motor control is needed. The commutator ensures a continuous circular motion of the armature in the brushed DC motor by changing current direction in the commutators wire coils. It is therefore not enough to fed the BLDC motor with a DC power source. To ensure a continuous rotation of the rotor in the BLDC motor an altering current must be applied by the motor controller to the motor. BLDC motors use an electronic commutation to alter the current supplied to the motor’s armature. Optical or magnetic transducers are used as rotor position sensors that supply informations on rotor position to the motors control system. The motor control system decides which stator phase should be energized base on the input signal from the rotor position sensor[28]. A motor control with the rotor position sensor gives an accurate torque and speed control of the motor. Figure 4.21 displays in three steps a simple explanation on the effect of altering the current in the BLDC motor. If a DC current would be applied to the motor, the rotor would hold its position as in figure 4.21b. In the first step the the current flows in a direction that magnetises the stator so the rotor is turned clockwise, figure 4.21a. The second step is where the rotor passes the stator’s poles, at this moment the current to the stator is switched off and the rotor’s momentum keeps the rotor rotating, figure 4.21b. At the third state, figure 4.21c, the stator is re- magnetised with reversed current, reversing the stators magnetic field. The rotor is now pulled again in clockwise direction. The electronic commutation of the voltage supplied to the armature Figure 4.21 is only a simplified construction of a BLDC motor. Using a single coils motor results in an unsteady torque. The torque is improved by heaving three or more coils as shown in figure 4.20. 4.3 Brushless DC permanent magnet electric motor 57

(a) (b) (c)

Figure 4.21: The basic operation of BLDC motor

An example of voltage applied to a six coil motor is shown in figure 4.22. This voltage could be applied to the motor in figure 4.20a, where Va’ is a coil with a same voltage supply as Va but wounded in the opposite direction resulting in the opposite magnetic field.

Figure 4.22: Voltage applied to the BLDC motor

”Brushless DC motor”is often considered not an entirely satisfactory name, because it really must be used with altering current to operate. A BLDC motor is called different names at different manufactures. The most common are self-synchronous AC motor, variable frequency synchronous motor, permanent magnet synchronous motor or electronically commutated motor (ECM). The name BLDC motor has though it’s point, the altering current to the motor must be variable frequency and so derived from DC power source. The torque-speed characteristics of the BLDC motor are also very similar to the brushed DC motor[31]. Similar to the brushed DC motor, the torque of the BLDC motor is proportional to the armatures current (except for some losses), assuming a constant flux produced by the permanent magnets. The motors torque can therefore be controlled by the input current to the motor’s armature, and equation 4.4 is valid. As for the brushed DC motor the BLDC motor can be used for reverse torque or regenerative braking, capturing the energy produces by deaccelerating the moped. For regenerative breaking the controller must be capable of operating the motor as an generator, reversing the armatures 58 DC motors current direction. The BLDC motor speed is proportional to the applied armature voltage at steady-state conditions, as for the brushed DC motor described above. The BLDC motor speed can therefore be sufficiently controlled by the applied armature voltage. The speed controller must though be current limited to protect the motor from overheating. The motor speed will however vary with load, the load can be affected by moped laden weight and variation on road slope. The BLDC motors are in general higher efficient than wound field motors, lighter weight, less space consuming and need less maintenance (no brushes to be replaced). BLDC need mored advantage motor control system, the system is required to convert the DC from the power source to a square wave current, the square wave must be controlled by the rotor position sensor. Some BLDC motors have very high power to weight ratio, as an example is the BLZ364S-48V-3500 motor from Anaheim Automation. The motor is rated 1.0[kW ] and weighs 4.5[kg], giving a power to weight ratio of 222.2[W/kg]. The BLZ364S-48V-3500 motor was considered for the projects application, but measurements lead to the conclusions that the motor is slightly too large and does not fit into the current moped frame. After long search, a BLDC motor was found that both fitted into the mopeds frame and was powerful enough to deliver reasonable acceleration and top speed. This is the HDM105E10-51S motor from SEM. The mopeds speed limit using this motor at variant gear ratios is shown in figure 4.23. The motor fits into the current mopeds frame, see Appendix D.3 for visual realizations on the fittings. Request on the motors prize was sent to SEM via e-mail, response from sales contact gave the information that the motor costs 5693DDK. E-mails are found in Appendix E. In the next section the valuation of BLDC hub motors will be done, the hub motor is expected to give some advantages over other addressed motor types as it would be place inside the mopeds wheel.

4.3.1 Wheel hub motors

Hub motors come in many diﬀerent types and sizes, the most common type is the BLDC hub motor. Therefore, in this paper the focus will be on BLDC hub motors. In the following section the principle of BLDC hub motor will be shortly introduced and how the motors could be implemented and ﬁtted in the moped. The wheel hub motor is an electric motor where the stator and the armature 4.3 Brushless DC permanent magnet electric motor 59

Figure 4.23: The mopeds maximum speed capabilities using the HDM motor from SEM 60 DC motors

(a) (b) (c)

Figure 4.24: BLDC hub motor

is placed in the center of the motor. The stator is often fixed to the wheel’s axle, where the rotor is fitted to the turning wheel. The concept of fitting a motor into a wheel was first introduced by Wellington Adams in 1884 [18] and in 1890 Albert Parcelle of Boston, MA developed the first fully incorporated Wheel hub motor [37]. The theoretical principle of torque-speed behavior of BLDC hub motor is similar to the brushed DC motor, introduced above. The BLDC hub motor works in theory the same way as BLDC motors, where the rotor and stator placements have been shifted. The hub motors field is displayed in figure 4.24a, the dark blue plate represents a magnet that is rotated around the motor by the changing magnet field emitted by the field windings. The magnet is placed inside the rotor case, displayed to the right in figure 4.24b. Full assemble of a hub motor with a tire is shown in figure 4.24c. The stator is placed around the tire’s axle, wires to connect the motor can also be seen in the figure. Wheel hub motors give great advantages, by placing the motor inside the mopeds tire a valuable space within the mopeds frame is gained. The space gained gives more flexibility on the placement of the systems electrical energy storage and the motor controller. The electrical energy storage could now be placed lower in the frame, giving more stability to the moped. The need for transmission system is eliminated by the use of wheel hub motor, lowering the moped weight. By using a wheel hub motor, the only rotating part on the moped will be the tires. The use of wheel hub motors has proven popular in bicycles. Great selection of hub motors under 500[W ] is available. The use of wheel hub motors in electric scooters seems to be emerging, theses hub motors are though often to large and powerful for this application. Finding a hub motor that fits into the current frame was found difficult. Some changes would have to be done on the mopeds frame if hub motor is to be used. 4.3 Brushless DC permanent magnet electric motor 61

4.3.1.1 MW-16C

The motor MW-16C is available at GoldenMotor, the MW-16C is a 2.0[kW ] to 3.0[kW ] BLDC hub motor weighing 9.5[kg] and is available for 250$ at manufactures homepage. Modeling the moped top speed at for different gear ratios and acceleration characteristics was done, using the motors data. The MW-16C motor is fitted into a 10”rim (272[mm] in diameter). The tire currently fitted on the moped is fitted on a 5”rim and has a total diameter of 310[mm]. To fit a 10”rim tire on the moped a tire with low hight must be selected. Low hight tire that fit on a 10” rim usually have a diameter of 40[mm] when proper inflated. Therefore a tire radius of r = 200[mm] is assumed when modeling the MW-16C hub. Same method was used to model the moped’s speed-gear ratio characteristics using the MW-16C motor data as was done using the motor data of the series motor 140-07 from Advanced Motors Inc. in section 4.2.1. The MW-16C motor is rated 2.0[kW ] to 3.0[kW ]. Motor tests results for input power of 145.2[W ] to 1.932[kW ] are provided by manufacture. The following values where obtained from motor test results and used in the top speed modeling, all motor data is found in Appendix B.5:

MW-16C motor Motor test data U 48.16 P 1.932[kW ] ω 756.2[rpm] τ 21.39[Nm] η 87.6% I 40.12[A]

The results of speed-gear ratio characteristics calculations are shown in ﬁgure 4.25. Using the gear ratio of G = 1 gives a top speed of 15.83[m/s] or 56.9[km/h]. Modeling of the acceleration characteristics was also done for the MW-16C motor. The maximum torque of 21.39[Nm] was read from motor test results, see Appendix B.5, and used in the simulation. The motor curves show that the motor speed drops linear when exceeded over the critical speed. The motors critical speed in the modeling is ωc = 756.21[rpm]. From the motor speed of 756.21[rpm] to 844.7[rpm], the motors torque falls from 21.39[Nm] to 0.12[Nm]. Assuming the motors torque is constant for motor speed under the critical motor speed and a linearity of the motors torque for motor speed from 756.21[rpm] to 844.7[rpm], the motors torque is deﬁned as: 62 DC motors

Figure 4.25: Modeling the mopeds top speed at diﬀerent gear ratios using the MW-16C BLDC hub motor from Golden Motors

τem = 21.39[Nm] for ωa ≤ ωc (4.32a)

τem = 203.131 − 2.295ωa for ωa >ωc (4.32b)

The same method was used to model the MW-16C motors acceleration characteristics as when modeling the LEM-130 acceleration characteristics. The results are shown in figure 4.26. The results from the two modeling, the MW-16C speed-gear ratio and acceleration characteristics, show similar results. The gear ratio of G = 1.0 is considered to be the optimal gear ratio for a the MW-16C motor, giving a moped maximum speed of 57[km/h]. It takes though approximately 45[sec] for the moped to reach the top sped limit. The acceleration from stand still is considered to be within an acceptable range, where the speed of 45[km/h] is reached within 20[sec]. After close inspection on the MW-16C motor’s fitting on to the moped, some difficulties came up. If the motor is to be placed as the front wheel, the mopeds front fork and damper would have to be changed or redesigned. The motor hub wheel is too wide to be fitted into the current front fork. When consider placing the motor as rear tire, the following difficulties came up:

The rear fender’s hight was too low, fender would have to be changed or redesigned. 4.3 Brushless DC permanent magnet electric motor 63

Figure 4.26: Modeling the mopeds acceleration characteristics using the MW-16C BLDC hub motor from Golden Motors

The rear light currently placed on the rear fender, when removing the fender the rear light would have to be replaced.

The rear number plate is currently placed in the rear fender, when removing the fender the rear number plate would have to be replaced.

The rear part of moped’s frame will have to be redesigned. Motor is too wide to ﬁt into the current frame, this can be done without eﬀecting the fold-ability.

Same diameter tire would have to be found for the front tire to get the moped leveled.

Breaking system would have to be redesigned. The current breaking system is mounted in the moped’s tires, by changing the tires to hub wheels requires a redesign in the breaking system.

4.3.1.2 EVT3kW

A hub motor with mounted disk-breaking system was found, Hub Motor EVT3kW from EVT. It is a 10”rim motor, same size as the MW-16C motor, but the EVT3kW motor is wider. The motor has been used in mopeds such 64 DC motors as Electric Vespa, EVT 168 and EVT 4000e. It is though considered to be a high cost solution, the motor is commercially available for 749$. This motor only solved one of many problems, breaking system, that arises when using a 10”hub motor. The moped’s maximum speed capability at diﬀerent gear ratios using the EVT3kW motor from EVT is shown in ﬁgure 4.27. The moped is estimated to be capable of 59[km/h] (16.4[m/s]) using the EVT3kW motor.

Figure 4.27: Modeling the mopeds speed capabilities at diﬀerent gear ratios using the EVT3kW BLDC hub motor from EVT

4.3.1.3 MW12B

To realize the capabilities of a hub motor that fits into the current moped frame, the hub motor MW12B was considered. The MW12B motor from Golden Motor is a 12” wheel motor, the same diameter size as the mopeds current tires and similar width. The inspection lead to the conclusion that the motor can be fitted into the current fork. When changing the front wheel, the front breaking system would have to be redesigned. Modeling of the 4.3 Brushless DC permanent magnet electric motor 65 motor lead to that conclusion that a moped using the MW12B motor is only expected to be capable of reaching 27.7[km/h] (7.7[m/s]). The modeling results are shown in figure 4.28.

Figure 4.28: Modeling the mopeds speed capabilities at diﬀerent gear ratios using the MW12B BLDC hub motor from Golden Motors

4.3.2 BLDC section discussion

The BLZ364S-48V-3500 motor from Anaheim Automation was considered to be a suitable motor for the moped. After further inspections it was concluded that the BLZ364S-48V-3500 motor does not fit into the current moped frame. Further research lead to the finding on the HDM105 motor from SEM, the motor fitted into the frame and is capable of giving the moped a maximum top speed of 15.8[m/s]. Using a wheel hub motor gives great advantages on gaining space inside the mopeds frame, where gained space can give more room for battery and control placement. Finding a wheel hub motor that fits into the current 66 DC motors frame, with or without breaking system, and that is powerful enough to meet the projects expectations has been found difficult. To justify the use of wheel hub motor, a motor with breaking system that is capable driving the moped at acceptable acceleration and top speed must be found. This was proven unsuccessful within the projects time limit. The relations of wheel size and motors torque/speed requirements needed to fulfill projects requirements have proven to be very rare. It is therefore not expected that a hub motor capable of meeting the projects requirements can be found on a commercial marked.

4.4 Motor comparison

The three motor types, brushed DC, series and BLDC motor are now further compared to narrow the motor selection to one motor. In the comparison, informations on 37 motors was obtained. The 37 motors compared where all traction motors, some of them are widely used as traction motors in EVs. The motors are from 500[W ] up to 21.5[kW ], costing from 517[DDK] to 9255[DDK]. The data-sheet with the collected informations is provided in Appendix C. Comparison on motor cost was done on the three motor types thought to be well suited for the application. Figure 4.29 shows the results from the comparison. The red, blue and green lines are representation on the fitted average value of the motors cost of variable sizes3. The comparison lead to the conclusion that the BLDC motor is generally a more costly solution and the series motor is the least costly of the three motor types compared. The brushed and BLDC motors use higher cost material, magnets, to form the motors magnetic field. Series motor do not contain magnets, as the magnetic field is produces by filed windings. The magnets are considered to be the cause of the cost difference between magnet motors and wounded motors. It is considered to be important to keep the vehicles weight limited, as the vehicle ranges depends on the vehicle’s laden weight. The mopeds main concept is it’s fold-ability and carry-ability, the carry-ability is highly dependent on the mopeds weight. It is therefore essential to select a motor with it’s weight in mind. Using the data collected for the 37 motors a comparison chart was made, see figure 4.30. Similarly as in figure 4.29, lines have been fitted that represent the average value of each motor’s type power to weight ratio. The results from the comparison lead to the conclusion that BLDC motors are generally less weight than the brushed and series motors. The brushed motor is however the motor weighing the most of the three motors.

3The plot was also made for separate motor type, see Appendix C. 4.4 Motor comparison 67

Figure 4.29: Cost comparison of brushed DC, series and BLDC motors. Where the red, blue and green lines represent the average ﬁtted value.

Figure 4.30: Weight comparison of brushed DC, series and BLDC motors. Where the red, blue and green lines represent the average ﬁtted value. 68 DC motors

The results of this comparison where compared to results from other studies. Studies on EV’s production and operation cost has been done by R.M. Cuenca, L.L. Gaines, and A.D. Vyas [38]. Among motor types considered in R.M. Cuenca’s paper are the series and BLDC motor types. In the paper a cost analysis is done by breaking the motor down to its main constituent elements. Thereafter, the cost of each element is determent. Motors cost is thereafter found as sum of main constituent elements cost. The cost for each motor is normalized on the basis of power delivered to obtain a cost per watt ﬁgure. Figure 4.31 displays R.M. Cuenca’s results. The results show that series motors are approximately 16% more space consuming then BLDC motors and weight approximately 60% more. The BLDC is though about 18% more costly.

Figure 4.31: Comparison of Series/shunt and BLDC motor, from [38]

The results obtained in R.M. Cuenca’s paper are consistent with the results found in this paper. The BLDC motor is both less space consuming and less weight, two valuable factors for the foldable moped. The cost must though be kept low. The 18% more cost of BLDC motors is consitered to be acceptable when space and weight trade-oﬀs are compared, making the BLDC motor the obtimum selection of the foldable moped. Chapter 5

Battery

Storing the electrical energy needed to propel EV’s is often considered to be the largest challenge. The EV has the reputation of being heavy and low range vehicle. The electrical energy storage systems used for EV’s is often low energy dense, making it large volume and heavy. With modern electrical energy storage technology, electric powered vehicles can be designed lighter and capable of longer range. In the selection of electrical energy storage system for the projects application, two academic papers will be used. In the ﬁrst paper a valuation on electrical energy storage systems for an electrical boat has been done by the author of this paper, Bjarni Gudmundsson [27]. In the second paper Krist- jan B. Bragason valuated the possibility of and advantages of upgrading the battery used in electric powered bicycles owned by DTU [20]. In the evaluation of electrical energy storage system for an electric boat, four electrical energy storage systems where evaluated. Here a draft from [27] ﬁndings on the four storage systems is provided:

1. Lead-acid batteries are one of the oldest battery technologies and remain widely used in modern cars SLI (start, lighting and ignition) systems. The lead-acid battery has been known for being reliable, robust and low cost. Sulfation occurs in all lead-acid batteries, causing the batteries short lifetime. The principle of lead-acid battery storage technology is based on the chemical reaction of lead Pb and an aqueous solution of sulfuric acid. Lead is one of the heavier elements known today, with the atomic mass of 207.2[u] and is used in the amount of 70 Battery

about 40-70% of the batterey total weight. Though lead-acid battereis are low cost, they are high weight and short lived.

2. Nickel-metal Hydride, or NiMH batteries have been available on commercial marked since 1989. NiMH where considered to be a break- through in battery technology as it was more energy dense and envi- ronmentally friendly than other available batteries. NiMH batteries where considered to be the replacement of NiCad battery technology. Because of the use of cadmium in NiCad, the battery has been banned in vehicle use by the EU. NiMH batteries suffer from memory effect, the effect is though reversible through several complete charge/recharge cycles. NiMH batteries have generally 2000-3000 cycle lifetime at 80% DOD (depth of discharge). The energy density is about twice the energy density of lead acid battery, or around 45−66W h/kg. Due to cost the NiMH was consitered to be the obtimal electrical energy storage system for the electric boat.

3. Lithium-ion, or Li-ion batteries where ﬁrst commercialized as secondary battery by Sony Corp. in 1991 or two years after the NiMH battery. High hopes where bound to both Li-ion and NiMH, the two types competed for domination on the portable applications marked. Safety issues on the Li-ion battery lead to drawbacks on the marked, the battery type raise again after development on the Li-ion battery manage system (BMS). Lithium is one of the lightest element found, with the atomic mass of 6.941[u], or 3.35% of lead’s atomic mass. This is what makes the Li-ion battery capable of its high energy density. Li-ion batteries are available from various energy density, from 72[W h/kg] upto 150[W h/kg], or about twice the energy density of NiMH batteries. Due to high cost on large batterie units, the Li-ion was consitered to be too expensive solution for the electric boat.

4. Fuel cell (FC) technology was considered to be an option for the 17[m] long and 7[m] wide electric boat where the PEM fuel cell was considered to be the most suitable fuel cell technology for the application. The FC technology was considered to be too expensive. Producing low cost hydrogen from a renewable source still remains a challenge that is not expected to be solved in near future. Hydrogen gas is also very difficult to store as it has very low density, or about 0, 0899kg/m3. Some of the already available FC vehicles are using pressured hydrogen gas in 700 bar tanks and cryogenic liquid hydrogen tanks. Pressurizing hydrogen and storing it at 700 bar takes somewhat energy and is today a high cost solution. The overall efficiency of the hydrogen fuel cell technology, from energy required to produce hydrogen to the energy delivered by the PEM fuel cell, is only approximately 44% at best, using today’s technology. This efficiency can be considered very poor 5.1 Li-ion 71

compared to the eﬃciency of other electrical energy storage systems.

NiMH battery technology was considered to be the best ﬁt as electrical energy storage system for the electric boat. This was mainly due to the high cost of the large Li-ion battery units. However, the low weight, long lifetime characteristics and high rate discharge capabilities of the Li-ion makes it the optimal solution for vehicle application. Li-ion batteries have already been proven reliable in mobile device application, and are the most used batteries in modern portable devices. Though the Li-ion technology is considered to be too expensive for large vehicle application the technology is considered to be already proven successful in smaller application. The technology of Li-ion has began to emerge in larger application, such as full size scooters, larger motorcycles and even sports cars. For the last resent years Li-ion batteries have been commercially available at reasonable prize. The FC technology was considered to be an option for the 17[m] long and 7[m] wide electric boat, that was in need of 360kWh. Fuel cell technology is too complex and expensive to be considered for a moped applications and is therefore not further addressed in this paper. Kristjan B. Bragason came to similar conclusion in his synthesis work, where Li-ion was considered to be the optimal selection as electrical energy storage system for a bicycle owned by DTU.

5.1 Li-ion

Over the recent years Li-ion batteries have been focused on energy storage development for EVs and HEVs applications. Li-ion batteries for EVs have been and still are making impressive improvements on speciﬁc energy, energy density, operating temperature, cycle life and safety. Li-ion battery technology has been known to be rather expensive, but at the same time a low weight solution. The development over the last years Li-ion cell’s material cost has been reduced and at the same time the cell’s speciﬁc energy is has being improved resulting in less cost per kwh.

5.1.1 Battery Management System

Because of safety issues, Li-ion batteries require a BMS that. The BMS, sometimes referred to as safety circuit, provides necessary solutions to meet safety requirements for the battery pack. Most often the BMS is built into the battery cell or pack, some manufactures provide it as a separate device. 72 Battery

The temperature of Li-ion batteries must be monitored by the BMS as Li- ion cells have been known to overheat to a hazardous level if not regulated. Overheating can be caused by a damaged cell case, short circuiting or if too high a recharging voltage is applied. If battery cells are connected in parallel BMS must be provided for each string of cells and the status of each cell string has to be continuously monitored. The BMS helps maintain all the relevant battery parameters, such as temperature, cell voltage and battery current, within their safety limits. Most Li-ion manufactures, if not all, provide a BMS solution for their product, this is done to ensure the safety of Li-ion battery products.

5.1.2 Types

Li-ion batteries are secondary, or rechargeable, batteries1 that are comprised of lithium intercalation compounds as positive or negative electrodes. When discharging/charging the Li-ion battery, lithium ions, Li+ exchange between the cathode and anode. Number of different materials have been used as electrodes in lithium batteries. Several types of Li-ion batteries are available today. Lithium cobalt oxide or LCO type lithium battery is the first Li-ion battery to be commercialized. Technology of LCO Li-ion battery was developed by the American physicist Dr. John Goodenough and late used by Sony when the corporation launched the first secondary Li-ion battery in 1991[36, 21]. Due to safety concerns and high cost, compared to other Li-ion batteries, the LCO has not been developed for larger battery pack applications[32, 25]. Therefore LCO not be addressed further in this report. Since the LCO Li-ion battery, several other lithium based (or lithium doped) materials have been successfully used as anode or cathode materials. The different materials give the battery different characteristics and capabilities. Table 5.1 from [27] is here reprinted to realize the difference of different Li-ion battery types. Table 5.1 shows that different Li-ion batteries have different discharge characteristic. The discharge voltage differ from 1.5[V ] on the LCO (lithium titan oxide) up 3.9[V ] on the NCA (nickel, cobalt and aluminum doped lithium) battery. What is within interest of this paper is the maximum charge and discharge current. The battery must be capable of operating at the high discharge current the motor operates on. The charging rate is also to be high as it defines the time it takes the battery to be recharged.

1Lithium batteries are also available as primary cell, these batteries are diﬀerently constructed and are not with in the interest of this project. 5.1 Li-ion 73

Table 5.1: General characteristics of diﬀerent Li-ion battery types

Battery Nominal Discharge Max. charge Max. disch. IR type voltage voltage current current NCA 3,6V 2,7 - 3,9V C/7 1C 1,5 mΩ LFP 3,2V 2,0 - 3,65V C/2 4C 10 mΩ nLFP 3,3V 2,0 - 3,6V 4C 30C 10 mΩ LTO 2,3V 1,5 - 2,9V 6C 6C 0.55 mΩ

The charging rate is deﬁned in C-rate, a common method of rating batteries. An example of the practical use of the C-rate here above an example of 36[V ] and 16[Ah] battery is provided:

Maximum discharge current

NCA: Idischarge = 16[A] · 1 = 16.0[A] LFP: Idischarge = 16[A] · 4 = 64.0[A] nLFP: Idischarge = 16[A] · 30 = 480.0[A] LTO: Idischarge = 16[A] · 6 = 96.0[A]

For this size of battery the NCA type would not be capable of providing the needed current for the HDM105E10 BLDC motor from SEM introduced in section 4.3. The HDM105E10 motor has a rated maximum peak current of 49[A], the 16[Ah] NCA battery pack would have to be used with a buck converter. More interesting is the charge ratings of the diﬀerent types. Here is how the C-rating is used to determine the batteries maximum charging current:

Maximum recharge current

NCA: Icharge = 16[A]/7 = 2.286[A] LFP: Icharge = 16[A]/2 = 8.0[A] nLFP: Icharge = 16[A] · 4 = 64.0[A] LTO: Icharge = 16[A]/7 = 96.0[A]

The maximum charging current limits the batteries charging time, the higher the allowable charging current is higher current rate can be applied to the battery when charging. This the directly eﬀects the charging time. The C-rate can be used to ﬁnd the minimum charge time of the battery: 74 Battery

Minimum recharge time

1[klst] NCA: tcharge = 1/7 = 7[klst] 1[klst] LFP: tcharge = 1/2 = 2[klst] 1[klst] nLFP: tcharge = 4 = 15[min] 1[klst] LTO: tcharge = 6 = 10[min]

As can be seen from the calculations above, the NCA battery has very limited recharging current, resulting in long recharge time. Making up for the long recharge time is the NCA’s high energy density, see table 5.2. Onthe other hand, the LTO (lithium titan oxide) battery is capable of recharging at very high current but has low energy density. The LFP (lithium iron phosphate, also known as LiFePO-cells of LiFe-cells) and the nLFP (nano technology engineered LiFePO-cells) are very similar. The nLFP is developed by A123 Systems and has several advantages over the LFP battery. The recharge and discharge current is much higher, the energy density is little more, and the lifetime is doubled.

Table 5.2: General characteristics of diﬀerent Li-ion battery types

Battery Energy Power Cycle Temperature type density density life@DOD range NCA 150Wh/kg 600W/kg 3000 @80% −30◦C to +60◦C LFP 100Wh/kg 3000W/kg 2500 @100% −30◦C to +60◦C nLFP 108Wh/kg 5300W/kg 7000 @100% −30◦C to +52◦C NCM 110Wh/kg 1300W/kg 3000 @100% NA LTO 72 Wh/kg 760W/kg 12000 @100% −40◦C to +55◦C

After reviewing the different types of Li-ion batteries it comes to the conclusion that NCA batteries have too limited recharge current that leads to long recharge time. The LTO batteries are considered to be too low energy dense. LFP and nLFP are therefore determent to be the optimal Li-ion battery type for the projects application. The prize of nLFP and LFP2 is similar, ca 6[DDK/W h] (1[$/W h]) [27]. By comparing the difference of nLFP and LFP in tables 5.1 and 5.2, it stands out that the nLFP has the advantage. The nLFP battery is capable of higher discharge current, higher charge current, higher energy dense and longer lifetime. The nLFP has recently been taken into use in DeWalt power tools, where they have proven powerful and reliable, see figure 5.13. By this

2Companies providing LFP Li-ion battery solutions: SAFT, K2 Energy Solutions, LiFeBatt and GAIA. 3Figure 5.1 is from http://ev.whitecape.org/insight/A123/A123batteries007.jpg 5.2 Battery design 75 it is concluded that the nLFP battery from A123 Systems is preferred over other LFP Li-ion batteries.

Figure 5.1: A123 System’s nLFP battery in DeWalt power tool battery unit.

5.2 Battery design

Having two separate battery units is considered to give great advantages. The two units are to be fitted on the bike at the same time in separate battery slots. Using both batteries gives greater range when needed. When light weight is preferred over range, one battery unit is to be places in the bike. Having more than one battery unit for each moped can reduce the recharge time of the moped by recharging one battery while the other is in use. Batteries are available in prefixed cases, see figure 5.2a. These battery units are available for reasonable prizes in different sizes. GoldenMotor provides FLP Li-ion battery packs at the following prizes:

• 36V/12Ah (432Wh) for 1919DDK ($326) that is 4.44DDK/Wh

• 36V/16Ah (576Wh) for 2325DDK ($395) that is 4.04DDK/Wh

• 48V/12Ah (576Wh) for 2450DDK ($416) that is 4.25DDK/Wh

• 24V/16Ah (384Wh) for 1643DDK ($279) that is 4.28DDK/Wh

The mopeds frame has limited space for battery units, fitting two battery units such as one from GoldenMotor could be a challenge. One battery unit can be fitted where the tank is currently placed. The battery must though be on the side, otherwise it does not fit under the seat as it should when 76 Battery

(a) Preﬁxed battery unit, ﬁgure from gold-(b) Examples of nLFP and LFP Li-ion bat- enmotor.com tery cells

Figure 5.2: Battery units and battery cells folded. Figure of the battery in scale to the moped is provided in Appendix D. Designing a battery unit for the moped is a possibility that is worthy to look into when prototype has been successfully made. By designing a battery unit for the moped, more capacity can be ﬁtted into the mopeds frame. Battery cells are provided by most of LFP and nLFP manufactures mentioned in footnote above. Customize battery units can be made using these cells, as done by DeWalt in ﬁgure 5.1. Chapter 6

Modeling of the electric moped

In the following section a range modulation of the moped will be done. The modulation will use the acceleration characteristics of the HDM105E10- 51S BLDC motor and the voltage characteristics of a LFP Li-ion battery. The moped will be range simulated according to European ECE-47 testing standard cycle. The modeling method is described by James Lowry in [31]. All matlab codes use to simulate are provided in Appendix A among detailed description on the code’s function.

6.1 Acceleration characteristics

The moped’s acceleration characteristics using the HDM105E10-51S motor are here simulated. It is necessary to simulate the acceleration characteristics of the mopes before a range simulation can be done. The acceleration characteristics of the moped will be used to deﬁne the driving cycle used in range simulation. The same method as used to simulate the acceleration characteristics of the LEM-130, PMG 132 and MW-16C motors is used here to simulate the acceleration characteristics of the moped using the HDM105E10-51S motor. The following values where obtained from the motors data sheet, see Appendix 78 Modeling of the electric moped

B, and used in the simulation:

τem = 17[N] , for ωa ≤ ωc G τem = 18 − 0.088 υ , for ωa >ωc rtire ωc = 125[rad/s] (or ca. 1200[rpm]) G = {1, 1.5, 2, 2.5}

rtire = 0.155[m], the mopeds tire radius.

mladen = 100[kg], the mopeds current weight plus 70[kg] driver. g = 9.8[m/s2] ◦ α = 0 , flat road is assumed. J = 3.2[kg cm2] dυ a = , acceleration is defined as differentiation of velocity. dt

Figure 6.1 shows the results from the simulation, the moped has a top speed of ca. 55[km/h] to 61[km/h] when the gear ratio is from 2.0 to 2.5. The acceleration is also reasonable at this gear ratio, reaching 50[km/h] within 10[s]. In the following simulations the gear ratio will assumed to be G = 2.5.

Figure 6.1: Modeling the mopeds speed capabilities at diﬀerent gear ratios using the BLDC HDM105 motor from SEM 6.2 ECE-47 circle simulation 79

6.2 ECE-47 circle simulation

The European ECE-47 simulation cycle is designed to be used for mopeds and motorcycle simulation, for estimations on emission and range. In this report the driving cycle will be used to estimate the driving range of the electrical moped. The ECE-47 cycle is deﬁned by accelerations in the following time intervals:

0 to 50[s ] WOT (Wide Open Throttle) at standstill.

50 to 65[s ] deceleration to 20[km/h] over the time period.

65 to 100[s ] 20[km/h] is maintained.

100 to 108[s ] deceleration to 0[km/h] over the time period.

108 to 110[s ] 0[km/h] is maintained.

Figure 6.2 shows the ECE-47 driving cycle plotted. Note that the acceleration from standstill the ﬁrst 50[s] is the same as the acceleration for G = 2.5 in ﬁgure 6.1.

Figure 6.2: Modeling the mopeds speed capabilities at diﬀerent gear ratios using the BLDC HDM105 motor from SEM 80 Modeling of the electric moped

6.3 LFP Li-ion voltage characteristics

Though the LFP Li-ion battery has rather ﬂat discharge curve, it is not constant. For more accurate simulation, the Li-ion batteries open circuit voltage must be described. Figure 6.3 displays an open voltage vs DOD characteristics of a LFP Li-ion battery at diﬀerent temperatures.

Figure 6.3: Discharge voltage of LFP Li-ion battery at diﬀerent temperatures, ﬁgure from phostechlithium.com

In the simulation a temperature of 25◦C will be assumed. Figure 6.4 shows the visual representation of function describing the Li-ion battery open circuit voltage at 25◦C used in the simulation.

Figure 6.4: Discharge voltage of LFP Li-ion battery used in the range simulation. 6.4 Range test 81

6.4 Range test

The simulation on the range the moped is expected to be capable of, begins by simulating one cycle of the ECE-47 driving cycle. The simulation is then ran until the battery capacity is below 10% of original charge. The matlap code of the one cycle simulation is provided in Appendix A with detailed commentering on the function of the code. The code is also described by the ﬂowchart shown in ﬁgure 6.5. Parameters for vehicle data, battery data and motor data must be set. The data input for the following simulation is in accordance with component selected from previous sections. The following data is:

Table 6.1: Data used in the ﬁrst range simulation

Input data for range simulation

mass: 100[kg] The mopeds laden mass area: 0.653[m2] The front areal with driver Cd: 0.9 Dragcoefficient 2.5 Gratio: 0.155[m] G/rtire G eff: 0.99 Transmission efficiency Regen ratio: 0 Portionofregenerativebreaking alpha: 0◦ Hill climbing urr: 0.015 Tire rolling resistance Pac: 10[W ] The average power consumed by the accessories Bat type: LI Battery type, LI is for LFP Li-ion battery NoCells: 15 Numberofcells(frac48[V ]3[V/cell]) Capacity: 24[Ah] Capacity of battery packs (2 ∗ 12[Ah]) k: 1.05 Peukertcoefficient* kc: 1.5 Estimatedcopperloss** ki: 0.1 Estimatedironloss** kw: 0.00001 Estimated windage loss** ConL: 20[W ] Estimated constant motor losses**

*Peukert coeﬃcient of Li-ion battery is usually 1.05 to 1.2 [24]. **The motor losses where not provided by manufacture, values from similar motor where therefore used. Figure 6.6 displays the results from the simulation. The results display the DOD vs distance traveled when driving according to the European ECE-34 driving circle standard. Results show a battery state of 91.3% DOD after 31.36[km]. The results are expected to be the maximum range the moped could travel as perfectr conditions are assumed. Number of factors that are not counted in the simulation aﬀect the driving range of the moped. The 82 Modeling of the electric moped

Figure 6.5: Flowchart of the range simulation. 6.4 Range test 83 factors neglected are fore example: wind, hill climbing and cold weather.

Figure 6.6: Results from ﬁrst range simulation, data used for this simulation is shown in table6.1.

It was considered to be interesting to see how the range was effected when changing some of the bikes characteristics parameters and battery capacity. In the following simulations, the black ”+” signs mark the same simulation as in figure 6.1, where original parameters from table 6.1 are used. The number of batteries has great influence on the mopeds range. In the previous simulation, two 48[V] and 12[Ah] batteries from GoldMotors where assumed, battery information is shown in Appendix B.7. A simulation was done when assuming one, two and three 48V/12Ah batteries. The moped weight is also changed when simulating the different number of batteries. Battery weight is 5.3[kg], therefore when simulating one or three batteries the weight difference is ±5.3[kg] accordance do battery weight. The simulation results are shown in figure 6.7. Using one battery gives a range of only 15.14[km], or approximately half of the range when using two batteries and one third when using three. The battery weight difference of one or three does not affect the range much and the range can therefore be assumed to 15.14[km] be appr. 48[V ]·12[Ah] = 26.3[m/W h]. Decreasing the mopeds drag coefficient can be done f.ex. by fitting a more streamline shell on the mopeds front, this is common in scooters designs. The current coefficient was estimated to be 0.9, coefficient of 0.6 could possibly be reached by more streamline design. Figure 6.8 shows the results when different drag coefficient was simulated, where the red marks a 84 Modeling of the electric moped

Figure 6.7: Results from range simulation when varying the number of batteries. Red: One battery, Black: Two batteries and Blue: Three batteries, other variables are according to table 6.1.

drag coefficient of Cd = 0.6 and the black marks Cd = 0.9. A drag coefficient of Cd = 1.1 was also inserted to see the effect of higher drag. The results yield a range gain of 8.66[km] when drag is lowered. Decreasing the mopeds weight does also have an effect on the driving range. In the first simulation the weight was assumed to be 100[kg]. To realize the effect of weight on the range has, three different weight inputs are simulated. Figure 6.9 shows the results of the different weight simulation. The weight difference of 100[kg] (from 50[kg] to 150[kg]) gave range different of 7.57[km], this results can give approximation of 75.7[m/kg] Lowering the tires rolling resistance can be done by fitting tires with lower rolling resistance as explained in section 2.3. A simulation was done with an input of tire rolling resistance of µrr = 0.005 and the results where compared to a moped with similar tires as currently in use. The simulation results are shown in figure 6.10. By selecting a lower rolling resistance tires a range of 3.25[km] could be gained. The above simulations show how some differences in the mopeds design can increase the mopeds range. A simulation with all the previous range increasing implementations was done. The results are shown in figure 6.11. Table 6.2 is provided to show the original values, black marks, and the optimized values. Other values in the simulation is according to table tab:simdata1. The results show that the range can be increased from 31.36[km] to 46.5[km], 6.4 Range test 85

Figure 6.8: Results from range simulation when varying the drag coeﬃcient. Red:Cd = 1.1 Black:Cd = 0.9 Blue:Cd = 0.6, other variables are according to table 6.1..

Figure 6.9: Results from range simulation when varying the weight. Red:Cd = 150[kg] Black:Cd = 100[kg] Blue:Cd = 50[kg], other variables are according to table 6.1. 86 Modeling of the electric moped

Figure 6.10: Results from range simulation when varying the tires rolling resistance. Black:µrr = 0.015 Blue:µrr = 0.005, other variables are according to table 6.1.

Table 6.2: Data used in the optimized design range simulation

Input data for optimized range simulation Variables Red Blue mass: 94.7[kg] 100[kg] Cd: 0.6 0.6 urr: 0.005 0.005 Capacity: 12[Ah] 24[Ah] 6.4 Range test 87 a diﬀerence of 15[km], when using the same battery capacity but optimizing the moped design.

Figure 6.11: Results from range simulation when optimizing all variables. Red: Optimized values with one battery Black: Original values with two batteries Blue: Optimized values with two batteries. 88 Modeling of the electric moped Chapter 7

Discussion

First part of this paper where the mechanical parts connected to the mopeds divetrain system. Some parts that are effecting the mopeds range capabilities are very easy to change, such as the mopeds tires. It is though not an acceptable solution to select tires with low rolling resistance and low road grip. The design must be optimized, safety must though not be lowered. Timing belt is currently used as a secondary transmission system on the moped. This is considered to be a good selection for the electric moped, the timing belt is low maintenance, no lubrication is needed, low noise and the efficiency is very high. The use of primary and secondary transmission system as done in the current design is not considered to be necessary. An electric motor machine has high starting torque, combustion engines do not, therefore the CVT system is not considered to be needed. The electric moped only needs the simplest transmission system, two pulley and one belt. Such a design lowers the total weight and results in longer range. One of authors main aims with this paper was to get familiar with different DC motor types. Some of the most common DC motor types where reviewed in this paper, among the possibility of using the type in the moped. Detailed description and analysis of each motor type was thought to be necessary. The detail description resulted in better understanding of motor behavior when used in a system such as an electric moped. The BLDC motor was considered to be the optimum selection for this project. It is generally less space consuming and lower weight than the other motor types reviewed in this paper. A BLDC hub motor was considered to be even better selection. But finding a motor that fitted into the current frame and was capable of 90 Discussion meeting the requirements was found unsuccessful. Because of the mopeds small tires it was considered to be very unlikely to find a hub motor that fitted into the current frame without major changes. Selecting a motor type was one thing, finding a motor within that type was another matter. One motor was found and used in the main simulations. The motor showed satisfying results and fits into the current frame. If the motor selection is in some way not satisfying, another motor can be found. It was found very time consuming to search for motors on the Internet, where informations where also often limited. Attending a motor exhibition is thought to be much more effective and should result in a better motor selection for the application. At exhibition, contacts can be set up and wide collections on motors can be compared. Designing and building a motor specifically for the application is another option worth looking into after prototype has been build and tested. Cus- tom made motor might give great advantages for large scale manufacturing. The battery type selection was based on the authors previous research. Li- ion have been, in the past, considered to be too costly for a application such as this one. Recent production methods and designs have lower the cost of larger Li-ion battery units, making Li-ion a reasonable selection for EV applications. Li-ion battery units intended for bicycle application are widely available, where BMS and recharging system are included. Such a system is thought to give advantages over custom made battery system in a prototype and low scale manufacturing moped. A custom made battery system will fit better into the frame design and higher capacity can be accomplished. Cus- tom making is though considered to be too expensive and time consuming for a prototype of low scale manufacturing. Prototype is expected to be more costly than an end product. The motor selected in this paper costs 5693DDK, and a single battery system costs up to 2450DDK. A prototype with one battery system should be enough to prove the concept of the foldable electric moped. Chapter 8

Conclusion

The first stage of the electric vehicle conversion of the foldable motorbike has now been done. Both mechanical and electrical parts affecting the vehicle range, acceleration and top speed have been closely looked at. The analysis of these parts indicated that some improvements can be done on the mopeds design. The improvements should be aimed to give the moped longer range, higher speed, better acceleration capabilities and improved safety. After issuing the main parts of the mopeds drivetrain, a simulation was done. The mopeds capabilities where simulation by MATLAB mathematical modeling its characteristics. Results from the electric moped simulation indicates that the mopeds range is effected by all of the parts issued in this paper. By optimizing the moped design, a range of 15[km] could be gained, making the moped capable of traveling total of 46[km] on a single charge. An electric vehicle conversion of the foldable motorbike is well doable, the cost of prototyping might be higher than goal cost of the design. This cost could though be lower by higher scale manufacturing.

Further works

The fist state of the design has been done in this report. Before building a functional prototype some further works need to be done. A motor controller and a throttle bar is needed, the input signal to the controller comes from a throttle bar. In the beginning if this project, it was the authors intension to design such a controller and build it as a part of 3 weeks course. Because of limited time it does not seem to be a possibility. Finding a motor controller 92 Conclusion and a throttle bar that fits the battery’s and motor’s specifications must therefore be found, before building a functional prototype. A 12[V] DC power source must also be implemented for the mopeds electrical accessories, such as light and horn system. Bibliography

[1] Advanced dc motors. Internet Webpage, August 2010. URL http:// evalbum.com/advdc.

[2] Electric vehicle photoalbum. Internet Webpage, August 2010. URL http://www.evalbum.com/.

[3] Windsor, products. Internet Webpage, Juny 2010. URL www. vbeltindia.com.

[4] Brewer machine & gear co., ﬂat belt pulleys. Internet Webpage, Juny 2010. URL www.brewertensioner.com.

[5] Motorcycle tires and tools: Motorcycle tires and tools and accessories. Internet Webpage, Juny 2010. URL http:// motorcycle-tires-tools.guide-n-service.com/sitemap1.html.

[6] Monarch bearing, power transmission equipment. Internet Webpage, Juny 2010. URL www.monarchbearing.com.

[7] Direct industry, products. Internet Webpage, Juny 2010. URL http:// www.directindustry.com.

[8] Gates corperation, industrial power transmission/synchronous belts. In- ternet Webpage, Juny 2010. URL http://www.gates.com.

[9] Orientrans power co., products. Internet Webpage, Juny 2010. URL www.cn-pt.com.

[10] Circular motion idlers, products/stamped steel idler pulleys. Internet Webpage, Juny 2010. URL www.circularmotionidlers.com.

[11] Dc-motor. Internet Webpage, Juli 2010. URL http://www.tps.ac. th/~panya/class/electro-magnetic1/dc-motor/index.html. 94 BIBLIOGRAPHY

[12] Di blasi industriale. Internet Webpage, Juny 2010. URL www.diblasi. it.

[13] Electric motors. Internet Webpage, Juli 2010. URL http://library. thinkquest.org/2763/Electricity/History/Inventions/Motor. html?tqskip1=1&tqtime=0929.

[14] Di blasi’s mopeds speciﬁcations. Internet Webpage, Juny 2010. URL http://diblasi.it/Caratteristiche.asp?Prd=R7&Lng=en.

[15] Schwalbe north america. Internet Webpage, Juny 2010. URL http:// www.schwalbetires.com/tech_info/rolling_resistance.

[16] Electric vehicle engineering and designer company. Internet Webpage, Juli 2010. URL http://vectrix.com.

[17] Roger A. Freedman Francis Weston Sears M. W. Zemansky A. Lewis Ford, Hugh D. Young. Sears and Zemansky’s university physics : with modern physics. Pearson Higher Education, 11.ed. edition, 2004.

[18] Wellington Adams. Electric motor. Patent No.300.827, United State Patent Oﬃce, 1884.

[19] Peter D. Blair. Modeling energy and power requirements of electric vehicles. Energy Conversion, 18(3):127 – 134, 1978. ISSN 0013-7480. doi: DOI:10.1016/0013-7480(78) 90011-6. URL http://www.sciencedirect.com/science/article/ B75D2-497T3M8-38/2/273d5462b5cbb52352bcc4de5f7b6ffc.

[20] Kristjan Bjorgvin Bragason. Upgrade of electrically driven bicycle. Syn- thesis report, Technical University of Denmark, DTU, 2009.

[21] Isidor Buchmann. Will lithium-ion batteries power the new millennium?

[22] David K. Cheng. Field and wave electromagnetics, volume 2. Addison- Wesley, 1989.

[23] Peter Clarke, Tariq Muneer, and Kevin Cullinane. Cut- ting vehicle emissions with regenerative braking. Transporta- tion Research Part D: Transport and Environment, 15(3):160 – 167, 2010. ISSN 1361-9209. doi: DOI:10.1016/j.trd.2009. 11.002. URL http://www.sciencedirect.com/science/article/ B6VH8-4YFDW6G-1/2/4531417e2ae3694be378ebe4a43f1281.

[24] A. Emadi. Handbook of automotive power electronics and Motor Drives. Boca Raton, FL: CRC Press 2005. ” BIBLIOGRAPHY 95

[25] David H. Swan Vernon P. Roan Michael P. Walsh Chairman Fritz R. Kalhammer, Bruce M. Kopf. Status and prospects for zero emissions vehicle technology: Report of the arb independent expert panel. Prepared for State of California Air Resources Board Sacramento, Cal- ifornia, April 2007.

[26] Charles A. Gross. Electric Machines. CRC Press, Taylor & Francis Group, 2007.

[27] Bjarni Freyr Gudmundsson. Electrical energy storage system for an electric boat: Analysis of diﬀerent electrical energy storage systems. Bachelor’s thesis, Technical University of Denmark, DTU, 2010.

[28] GERALD B.KLIMAN HAMID A.TOLIYAT, editor. HANDBOOK OF ELECTRIC MOTORS. Taylor & Francis Group, second edition, 2004.

[29] Hans Henrik Hansen (DEFU) Hans Andersen (DEFU). Energioptimer- ing ved elmotordrift. drevanalysei praksis, teknisk rapport 380,. Tech- nical report, DEFU, 1997.

[30] Nehemiah Hawkins. Hawkins Electrical Guide, volume 1. Theodore Audel & Company, 1914.

[31] John Lowry James Larminie. Electric Vehicle Technology Explained. John Wiley & Sons, 2003.

[32] Ken Kurani Jonn Axsen, Andrew Burke. Batteries for plug-in hybrid electric vehicles (phevs): Goals and the state of technology circa 2008. Institute of Transportation Studies, University of California, May 2008.

[33] Mueller. Electric vehicle drives, 1960.

[34] Travis Reeder My Ton, Chris Calwell. The choose green report: Low rolling resistance tires. Technical report, Green Seal Inc., 2003. URL http://greenseal.org/resources/reports/CGR_tire_ rollingresistance.pdf.

[35] U.S. Department of Energy. Electrical science volume 2 of 4, dc motor theory. Washington, D.C. 20585, June 1992. URL http://www.tpub. com/content/doe/h1011v2/css/h1011v2_106.htm.

[36] Oﬃce of Scientiﬁc & Technical Information. John b. goodenough, cathode materials, and rechargeable lithium-ion batteries. Internet site, Site visited in December 2009. http://www.osti.gov/accomplishments/goodenough.html.

[37] Albert Parcelle. Electromotor traction wheel. Patent No.320.690, United State Patent Oﬃce, 1890. 96 BIBLIOGRAPHY

[38] L.L. Gaines R.M. Cuenca and A.D. Vyas. Evaluation of electric vehicle production and operating costs. Technical report, Center for Trans- portation Research, Energy Systems Division 1999. ” [39] Carl Vogel. Build Your Own Electric Motorcycle. The McGraw-Hill Companies, Inc., 2009.

[40] Theodore Wildi. Electrical Machines, Drives, and Power Systems. Prentice Hall, 2002. Appendix A

Matlab codes

A.1 Accelerating characteristics

% This matlab code is for mopeds accelerating characteristics t=linspace(0,100,1001); vel=zeros(1,1001); d=zeros(1,1001); dT=0.1; for n=1:1000 if vel(n)<8.65 vel(n+1)=vel(n)+dT*(1.93-(0.001413*(vel(n)^2))); elseif vel(n)>=8.65 vel(n+1)=vel(n)+dT*(8.9-(0.81*vel(n))-(0.001413*(vel(n)^2))); end; d(n+1)=d(n)+0.1*vel(n); end; vel=vel.*3.6; figure(1) plot(t,vel,’k’);axis([0 100 0 100]); xlabel(’Time/seconds’); ylabel(’Velocity/km/h’); title(’prufuplot’); 98 Matlab codes

%hold on figure(2) plot(t,d);axis([0 30 0 200]);

A.2 Eﬃciency map

% This code is to plot a motors efficiency map

% First, arrays for range need to be set x=linspace(1,500); % Speed in rad/s y=linspace(1,40); % Motors torque range

% Now defining some constants kc=1.5; % For copper losses ki=0.1; % For iron losses kw=0.00001; % For windage losses tf=0; % For friction torque ConL=20; % Constant loss

% Now making a mesh [X,Y]=meshgrid(x,y);

P_out=(X.*Y); % Equation for the output power P_fr=X.*tf; % Friction losses P_wp=(X.^3)*kw; % Windage loss P_cl=(Y.^2)*kc; % Copper losses P_il=X*ki; % Iron losses

%Defining the input power P_in=P_out+P_fr+P_wp+P_cl+P_il+ConL;

Z=P_out./P_in; % Now setting the efficiency

% Now seting the efficiencies that will be plotted V=[0.5, 0.6, 0.7, 0.8, 0.85, 0.87, 0.88]; box off gri off contour(X,Y,Z,V); xlabel(’Speed/rad.s^-^1’),ylabel(’Torque/Nm’); A.3 ECE-47 circle simulation 99

A.3 ECE-47 circle simulation

% *************** .: ECE 74 :. ****************** % This script file is to model the Europaen test % driving cycle ECE 74. The ECE test driving % cycle is in general used for emission testing % on vehicles with engines less than 50cm^3. % It is also commonly used range simulations for % electric scooters. % ***********************************************

% One driving cycle lasts 110[s], therefore one % dimensional array for velocity readings is set, % one for every second. V=zeros(1,111); elbike; % - The drive cycle is build on % the mopeds acceleration % characteristics, elbike is % the file name of acceleration % modeling,here the informations % of that modeling is used. This % gives more accurate results.

% The first 50[s]the vehicle accelerates at full % power. for n=1:51 % - In the modeling of the elbike, V(n)=vel(((n-1)*10)+1); % values where found for every end; % 0.1[s], therefore the readings % are decemated here.

% The velocity is thereafter reduced down to % 5.56[m/s] over the next 15[s]. decel=(V(51)-5.56)/15; for n=52:65 V(n)=V(n-1)-decel; end

% Now the velocity of 5.56[m/s] is remained for % 35[s]. for n=66:101 V(n)=5.56; end; 100 Matlab codes

% Next the scooter velocity is reduced to standstill % over 8[s] timeinterval. decel=5.56/8; for n=102:108 V(n)=V(n-1)-decel; end;

% The mopeds speed is held zero over three seconds. V(109)=0; V(110)=0; V(111)=0; plot(V*3.6)

A.4 LFP Li-ion voltage characteristics function E_oc=open_circuit_voltage_LiIon(x,N) % Find the open circuit voltage of a nickel cadmium % battery at any value of depth of discharge % The depth of discharge value must be between % 0 (fully charged) and 1.0 (flat). if x < 0 error(’Depth of discharge <0.’) end if x > 1 error(’Depth of discharge >1’) end

% The Li-ion ocv is approximately linear over four distinct % steps, 0 to 0.02, 0.02 to 0.5, 0.5 to 0.82, 0.82 to 0.9, % 0.9 to 0.98 and 0.98 to 1.0 depth of discharge. % % N is the number of cells if x < 0.02 E_oc= (3.6 - (17.5*x)) * N; return; end

if x < 0.5 E_oc= (3.252 - (0.1041667*x)) * N; return; end A.5 One test cycle 101

if x < 0.82 E_oc= (3.356 - (0.3125*x)) * N; return; end

if x < 0.9 E_oc= (4.125 - (1.25*x)) * N; return; end

if x < 0.98 E_oc= (6.375 - (3.75*x)) * N; return; end

if x >= 0.98 E_oc= (37 - (35*x)) * N; return; end % Four different formulas for the three segments of the % discharge curve. return;

A.5 One test cycle

% ************* .: ONE CYCLE :. *************** % This script file performs one driving cycle, % on the simulated route. The cycle simulation % has N points and can can be used with any % vehicle using Li-ion or NiCad batteries. % All the appropriate variables must be set % by calling program. % ********************************************* for C=2:N accel=V(C)-V(C-1); Fad = 0.5*1.2*area*Cd*V(C)^2; % - Defining the force if % airdrag Fhc = mass*9.8*sin(alpha); % - Force of hill climbing Fla = 1.013*mass*accel; % - The force of linear 102 Matlab codes

% acceleration, the motors % inertia is estimated to % give and extra weight % factor of 1.05.

% Now defining the tractive effort needed to overcome the % four different forces. Pte = (Frr + Fad + Fhc + Fla)*V(C); omega = Gratio * V(C); % - Defining the motors % angular velocity as a % function of the gear % ratio.

if omega == 0 % - If vehicle is stationary Pte=0; % the following rules Pmot_in=0; % - No power into motor Torque=0; % - And no torque eff_mot=0.5; % - A dummy value, only set % to ensure no divetation % with zero elseif omega > 0 % - When the angular % velocity is more than % zero the vehicle is at % some velocity. if Pte < 0 Pte = Regen_ratio * Pte; % - Reduce the power if % breaking, end; % as not all will be by % the motor.

% We no calculate the output power of the motor, which % is different from that at the wheels, because of % transmission losses. if Pte>=0 Pmot_out=Pte/G_eff; % - Motor power > shaft power elseif Pte<0 Pmot_out=Pte * G_eff;% - Motor power diminished if end; % engine breaking.

Torque=Pmot_out/omega; % - Defining the relations of % motor power, torque anf % it’s angualr velocity.

% Defining the motors efficiency using the method A.5 One test cycle 103

% discussed in section Motor Efficiency if Torque>0 eff_mot=(Torque*omega)/((Torque*omega)+((Torque^2) *kc)+(omega*ki)+((omega^3)*kw)+ConL); elseif Torque<0 eff_mot=(-Torque*omega)/((-Torque*omega) + ((Torque^2)*kc)+(omega*ki)+((omega^3)*kw)+ConL); end; if Pmot_out>=0 Pmot_in = Pmot_out/eff_mot; elseif Pmot_out < 0 Pmot_in = Pmot_out * eff_mot; end; end;

Pbat = Pmot_in + Pac; % - The battery needs to power the % motor and other equipmtne in the % vehicle, such as the lights.

% The moedl can be used to simulate NiCad batteries % and Li-ion if bat_type==’NC’ E=open_circuit_voltage_NC(DoD(C-1),NoCells); elseif bat_type==’LI’ E=open_circuit_voltage_LiIon(DoD(C-1),NoCells); else error(’Invalid battery type’); end;

if Pbat > 0 I = (E - ((E*E)-(4*Rin*Pbat))^0.5)/(2*Rin); CR(C) = CR(C-1) +((I^k)/3600); elseif Pbat==0 I=0; elseif Pbat <0 % - When pattery power is negative the % motor is producing electric power, % and the system is regenerating power % from breaking system. Pbat = -1 * Pbat; I = (-E + (E*E + (4*2*Rin*Pbat))^0.5)/(2*2*Rin); CR(C) = CR(C-1) - (I/3600); end;

DoD(C) = CR(C)/PeuCap; 104 Matlab codes

if DoD(C)>1 DoD(C) =1; end

% Since one second time intervals are being taken, the % distance traveled every second is the same in meters % as the velocity. This must therefore be divited by % 1000 to obtain km.

D(C) = D(C-1) + (V(C)/1000); XDATA(C)=C; YDATA(C)=eff_mot; end;

A.6 Range simulation

% ********* .: EV Range Modelling :. ************* % This script file is to model an electric vehicle % driving standard test drive cycles, such as the % European cycles ECE-15 or ECE-47. The simulation % is for EV’s range measurements. Simulation will % continue running test cycles untill the battery % capacity is below 10% of full charge state. % ***********************************************

ECE_47; % - Here loading the test cycle, speed % should be defined in an array named % ’V’ and should be in m/s N=length(V); % - Number of readings in the array V

% ------% .: Data inputs for the vehicle :. % ------mass = 100; % - Vehicle’s laden veight [kg] area = 0.653; % - Vehicle’s frontal area Cd = 0.9; % - Vehicle’s drag coefficient Gratio = 2.5/0.115; % - Gear rato and tire size [1/m] G_eff = 0.99; % - Transm. efficiency (0.0 to 1.0) Regen_ratio = 0; % - Proportion of regenerative breaking % dony bu the motor (0.0 to 1.0) A.6 Range simulation 105 alpha = 0; % - Angle of road surface [rad] urr = 0.015; % - Tires rolling resistance Pac=10; % - The avg power to el. accessories. % ------% .: Data inputs for battery :. % ------bat_type=’LI’; % - Battery typa (LI for Li-ion or NC % for NiCad) NoCells=15; % - Number of cells % (cells in battery * number of batteries) Capacity=24; % - Battery capacity k=1.05; % - The Peukert coefficient

% ------% .: Data inputs for motor :. % ------kc=1.5; % - Copper lossoes ki=0.1; % - Iron losses kw=0.00001; % - Windage losses ConL=20; % - Constant motor losses

% Now finding some constants Frr=0.007 * mass * 9.8; % - Tire to roead surface % friction constant Rin = (0.06/Capacity)*NoCells; % - Battery internal resistance Rin = Rin + 0.004; % - Cable connection resistance % added to the battery % resistance.

PeuCap = ((Capacity/5)^k)*5;

% Now setting up arrays for storing data for the % battery, and distance traveled. All are set to % zero to begin with. These first arrays are for % the storing the values at the end of each cycle. % It is assumed that no more than 100 of any cycle % is completed. DoD_end = zeros(1,100); CR_end = zeros(1,100); D_end = zeros(1,100);

% Now setting arrays for use within each cycle DoD=zeros(1,N); % - Depth of discharge 106 Matlab codes

CR=zeros(1,N); % - Charge removed from the battery, % Peukort is used to regulate the % battery voltage. D=zeros(1,N); % - Record of distance traveled XDATA=zeros(1,N); YDATA=zeros(1,N); CY=1; % - CY is used to controll the outer % loop, and counts the number of % cycles completed. Cycling is % repeated until the batteries % capacity is down to 10% of fully % loaded battery. DD=0; % - DD is used to monitor the % discharge and loop % controll the loop. Lopp will run as % long as DD is less than 0.9. while DD < 0.9 % **** .: Simulation cycle begins :. **** One_cycle;

% Now cycle values are updated DoD_end(CY) = DoD(N); CR_end(CY) = CR(N); D_end(CY) = D(N);

% Inner arrays are now reset for the next % cycle. DoD(1)=DoD(N); CR(1)=CR(N);D(1)=D(N); DD=DoD_end(CY);

% **** .: Simulation cycle ends :. ****

CY = CY+1; end plot(D_end,DoD_end,’k+’); Appendix B

Motor and battery data 108 Motor and battery data B.1LEM-130fromLynchMotorCompanyLTD. 109

B.1 LEM-130 from Lynch Motor Company LTD.

B.1.1 Mechanical Drawing 110 Motor and battery data

B.2 PMG 132 from PERM MOTOR

B.2.1 Mechanical Drawing B.2PMG132fromPERMMOTOR 111

B.2.2 Motor-curves 112 Motor and battery data B.2PMG132fromPERMMOTOR 113 114 Motor and battery data B.3 AMG from Iskra 115

B.3 AMG from Iskra

Figure B.1: AMG Iskra motor data 116 Motor and battery data B.4 Advanced Motor & Drives 117

B.4 Advanced Motor & Drives

B.4.1 140-07-4001 118 Motor and battery data B.4 Advanced Motor & Drives 119 120 Motor and battery data B.4 Advanced Motor & Drives 121

B.4.2 A00-4009 122 Motor and battery data B.4 Advanced Motor & Drives 123 124 Motor and battery data B.5MW-16CBLDChubmotorfromGoldenmotor 125

B.5 MW-16C BLDC hub motor from Golden motor

B.5.1 Mechanical Drawing 126 Motor and battery data

B.5.2 Motor curves and data B.5MW-16CBLDChubmotorfromGoldenmotor 127 128 Motor and battery data

B.6 HDM105E10-51S from SEM B.6HDM105E10-51SfromSEM 129 130 Motor and battery data B.7LiFePObatteryfromGoldMotrrs 131

B.7 LiFePO battery from GoldMotrrs 132 Motor and battery data Appendix C

Motor Comparison 134 Motor Comparison 135 136 Motor Comparison Appendix D

Component ﬁttings into frame

D.1 LEM-130 from Lynch Motor Company LTD.

Figure D.1: The LEM-130 ﬁtted into frame, side view. Motor size has been scaled. 138 Component ﬁttings into frame

Figure D.2: The LEM-130 ﬁtted into frame, bottom view. Motor size has been scaled.

D.2 PMG 132 from PERM MOTOR GMBHD. D.3HDM105E10-51SfromSEM 139

Figure D.3: The PMG 132 ﬁtted into frame, side view. Motor size has been scaled. Red area is where motor collides with tire, motor does not ﬁt into the frame.

D.3 HDM105E10-51S from SEM 140 Component ﬁttings into frame

Figure D.4: The HDM105E10-51S motor from SEM ﬁtted into frame, bottom view. Motor size has been scaled.

Figure D.5: The HDM105E10-51S motor from SEM ﬁtted into frame, side view. Motor size has been scaled. D.4LFPbatteryfromGoldenMotors 141

D.4 LFP battery from GoldenMotors

Figure D.6: An LFP battery from GoldenMotors ﬁtted into frame, top view. Bat- tery size has been scaled. 142 Component ﬁttings into frame

Figure D.7: An LFP battery from GoldenMotors ﬁtted into frame, side view. Battery size has been scaled. Appendix E

E-mails

E.1 Advanced Motor & Drives

Subject: Motor information request From: Bjarni Freyr Gudmundsson Date: Tue, August 10, 2010 10:48 am To: [email protected], [email protected] Priority: Normal Options: View Full Header | View Printable Version

Dear Per Stenberg

My name is Bjarni and I am a student at the Danish Technical Univercity. I am currently working on a small electric vehicle conversion project. For the project I need a motor of ca. 2.5 HP.

From my internet research I found a 2HP series DC motor from Advanced Motors & Drives. The following information I got about the motor: 140-07-4001, 24-36V, 2.0 HP, 10 HP peak, (5.5")

Is it possible to get more information about this motor? I have limited space for the motor and the vehicle performance must fulfyll required expectations. 144 E-mails

If possible, I would need motor technical data and motors engineering drawings.

...... M.Sc. Electrical Engineer, student Bjarni Freyr Gudmundsson

DTU, Dep. Electrical Engineering Technical University of Denmark DK-2800 Kgs. Lyngby DENMARK Phone: +45 28 777 112 E-mail:[email protected] Web: www.elektro.dtu.dk

Subject: EVA Information From: [email protected] Date: Wed, August 11, 2010 6:01 pm To: [email protected] Priority: Normal Options: View Full Header | View Printable Version

Bjarni -

Advanced DC asked us to help you out.

In response:

1. My name is Bjarni and I am a student at the Danish Technical Univercity. I am currently working on a small electric vehicle conversion project. For the project I need a motor of ca. 2.5 HP.

From my internet research I found a 2HP series DC motor from Advanced Motors & Drives. The following information I got about the motor: 140-07-4001, 24-36V, 2.0 HP, 10 HP peak, (5.5")

Is it possible to get more information about this motor? I have limited space for the motor and the vehicle performance must fulfyll required expectations.

If possible, I would need motor technical data and motors engineering drawings. E.1 Advanced Motor & Drives 145

I have attached the information for the 140-07-4001 ( $450 ) and the A00-4009 ( $575 ). We stock the A00-4009. It would take 2-4 weeks to get the 140-07-4001.

Bryan @ EVA *********** [email protected]_ (mailto:[email protected]) _www.EVAmerica.com_ (http://www.evamerica.com/) (603) 569 - 2100

Subject: VS: motor price From: Henrik Søholm Date: Wed, August 25, 2010 7:43 am To: [email protected] Priority: Normal Options: View Full Header | View Printable Version

Hej Bjarni

Du har spurgt p˚aen motorpris p˚afølgende servomotor type HDM105E10-51S listepris kr.5693,-

Prisen er ekskl. moms fragt og emballage.

Med venlig hilsen / Best regards Henrik Søholm ______

Ulvehavevej 42-46 DK-7100 Vejle Tel.: +45 79 42 80 80 Dir: +45 79 42 80 82 Mobil: +45 21 78 54 04 E-mail: [email protected] Website: http://www.servotech.dk

-----Oprindelig meddelelse----- Fra: Bryon Ian [mailto:[email protected]] Sendt: 24. august 2010 15:36 Til: Henrik Søholm Emne: FW: motor price 146 E-mails

Hello Henrik,

Please can you pick up the enquiry below.

Thanks

Best Regards Ian Bryon Key Account Manager SEM Ltd

Tel 01689 884706 Fax 01689 884884

-----Original Message----- From: Bjarni Freyr Gu mundsson [mailto:[email protected]] Sent: 24 August 2010 14:31 To: Info (SEM) Subject: motor price

What is the price on the HDM105E10-51S brushless servomotors?

......

M.Sc. Electrical Engineer, student

Bjarni Freyr Gu mundsson

DTU, Dep. Electrical Engineering

Technical University of Denmark DK-2800 Kgs. Lyngby

DENMARK

Phone: +45 28 777 112

E-mail: [email protected]

Web: www.elektro.dtu.dk Appendix F

Figures of the moped

Figure F.1: The motors total length must be less than 230[mm]. 148 Figures of the moped www.elektro.dtu.dk

Department of Electrical Engineering Technical University of Denmark Ørsteds Plads Building 348 DK-2800 Kgs. Lyngby Denmark Tel: (+45)45253800 Fax: (+45)45931634 Email: [email protected]