energies

Article Permanent with Different Structures for in High Speed Trains

Marcel Torrent 1,*, José Ignacio Perat 1 and José Antonio Jiménez 2

1 Department of Electrical Engineering (DEE), Universitat Politècnica de Catalunya UPC BARCELONATECH, EPSEVG, Víctor Balaguer 1, 08800 Vilanova i la Geltrú, Barcelona, Spain; [email protected] 2 Faculty of Civil Engineering, Universitat Politècnica de Catalunya UPC EPSEVG, Víctor Balaguer 1, 08800 Vilanova i la Geltrú, Barcelona, Spain; [email protected] * Correspondence: [email protected]

 Received: 15 May 2018; Accepted: 11 June 2018; Published: 13 June 2018 

Abstract: In this work we proposed to study the use of permanent magnet synchronous motors (PMSM) for railway traction in the high-speed trains (HST) of Renfe Operadora (the Spanish national railway operator). Currently, induction motors (IM) are used in AVE classes 102–112 trains, so, the IM used as a traction motor in these trains has been studied and characterized by comparing the results with data provided by Renfe. A PMSM of equivalent power to the IM has been dimensioned, and different electromagnetic structures of the PMSM rotor have been evaluated. The simulation by the finite element method and analysis of the equivalent electrical circuit used in all the motors have been studied to evaluate the performance of the motors in this application. Efficiency is calculated at different operating points due to its impact on the energy consumption of railway traction. The implementation of the PMSM evaluated is recommended, mainly due to the improvements achieved in efficiency as compared with the IM currently used.

Keywords: permanent magnet motors; induction motors; road vehicles; energy efficiency; traction motors

1. Introduction The use of electrical drives in electric traction for high-speed trains has evolved from DC drives to AC drives [1,2]. One of the main reasons AC drives are used is due to the evolution of power electronics applied to these drives, for example, the functional improvement of inverters and the use of techniques. In addition, it is worth highlighting the lower maintenance requirements and greater reliability, as well as the high efficiency and power density offered by AC drives [3]. Among AC drives, IM was mainly used initially, but the trend in recent years has been to use PMSM, initially with excitation using coils and later with excitation using permanent [4]. Examples of this evolution are the TGV trains in France, where DC drives have been used in the TGV Paris–South East (year 1981, with motors of 535 kW and power density 2.9 kg/kW), AC drives with synchronous motor of rotor wound in the TGV Atlantique (year 1989, with motors of 1130 kW and power density 1.35 kg/kW), AC drives with asynchronous motor in the Eurostar (year 1994, with motors of 1020 kW and power density 1.23 kg/kW), and AC drives with permanent magnet synchronous motor in the AGV (year 2004, with motors of 760 kW and power density 1 kg/kW). The current trend seems to indicate that in the coming years drives with PMSM will be used in the HST preferentially [5,6]. A new trend, still in the experimental phase, points to the possibility of using linear synchronous motors with permanent magnets, also incorporating superconducting materials [7].

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InEnergies the 2018 beginning, 11, x FOR PEER of the REVIEW Spanish High Speed, Renfe used salient pole synchronous2 of motors. 17 However, the trains are currently being fitted with induction traction motors. Recently, HST have been using linear synchronous motors with permanent magnets, also incorporating superconducting fitted with permanent magnet synchronous motors, just like French and Italian AGV trains. materials [7]. The PMSMsIn the beginning give high of efficiency the Spanish and High a better Speed, power/weight Renfe used salient ratio pole (power synchronous density) motors.with higher manufacturingHowever, the and trains materials are currently cost. being Permanent fitted with magnet induction synchronous traction motors. motors Recently, [8,9] HST appear have as an interestingbeen fitted alternative with permanent for several magnet reasons, synchronous such as: motors, the elimination just like French of rotor and Italian copper AGV losses, trains. increased efficiency,The higher PMSMs power give high density, efficiency lower and rotor a better momentum power/weight of inertiaratio (power and thedensity) possibility with higher of using regenerativemanufacturing brakes and even materials at low cost. speeds. Permanent On the magnet other hand, synchronous PMSMs motors have several [8,9] appear disadvantages, as an suchinteresting as the constant alternative flux fo providedr several reasons, by the such magnets as: the and elimination high costs of rotor due copper to the losses, increased increased price of rare-earthefficiency, magnets. higher PMSMs power can density, be classified lower rotor according momentum to magnet of inertia arrangements, and the possibility i.e., surface of using magnets, and interiorregenerative magnets brakes with even radial at low or speeds. tangential On the magnetization. other hand, PMSMs Surface-mounted have several permanent disadvantages, magnet such as the constant flux provided by the magnets and high costs due to the increased price of rare- motors behave like synchronous motors with a cylindrical rotor, where the torque is solely obtained by earth magnets. PMSMs can be classified according to magnet arrangements, i.e., surface magnets, the interactionand interior between magnets thewith rotor radial flux or andtangential mag current.netization. Similar Surface to salient-mounted pole permanent synchronous magnet motors, the reluctancemotors behave torque like must synchronous be considered motors inwith interior a cylindrical permanent rotor, where magnet the motors. torque is solely obtained Thisby the work interaction studies between the alternative the rotor use flux of and a PMSM stator in current. place ofSimilar the IM to used salient in pole AVE synchronous trains of classes 102–112.motors, Initially, the reluctance the behavior torque ofmust the be IM considered currently in usedinterior was permanent analyzed magnet [10]. Parametricmotors. estimations of similarThis traction work studies motors the were alternative conducted use of when a PMSM there in wasplace a of lack the IM of usednecessary in AVE technical trains of data. The electromagneticclasses 102–112. Initially, structure the of behavior the IM was of the simulated IM currently by the used finite was element analyzed method, [10]. Parametri the operationc was analyzedestimations from of similar its equivalent traction motors circuit, were and conducted finally, the when results there from was thea lack calculations of necessary of technical model were data. The electromagnetic structure of the IM was simulated by the finite element method, the compared with actual test bench measurements of the motor. Additionally, iron and mechanical losses operation was analyzed from its equivalent circuit, and finally, the results from the calculations of were also analyzed and compared with actual measurements, and hence, the procedure of calculations model were compared with actual test bench measurements of the motor. Additionally, iron and usedmechanical in the IM was losses verified were also in order analyzed to apply and itcompared to the PMSM. with actual measurements, and hence, the Insteadprocedure of of IM, calculations the alternative used in use the of IM a PMSMwas verified was proposed.in order to apply Three it different to the PMSM. magnet arrangements were consideredInstead of for IM, the the PMSM: alternative surface use magnets, of a PMSM and interior was proposed. magnets Three with different radial or magnet tangential magnetization.arrangements The were analysis considered of thesefor the structures PMSM: surface involved magnets, the and simulation interior magnets of their with electromagnetic radial or structurestangential and application magnetization. of methods The analysis to quantify of thesemotor structures losses. involved A power the balance simulation was of also their used to calculateelectromagnetic the efficiency structures and power and application density. of methods to quantify motor losses. A power balance Finally,was also theused functional to calculate performance the efficiency ofand the power proposed density. PMSM and the IM were compared and the Finally, the functional performance of the proposed PMSM and the IM were compared and the cost of manufacturing materials was evaluated. cost of manufacturing materials was evaluated. 2. AVE Trains Classes 102-112 2. AVE Trains Classes 102-112 The mainThe main characteristics characteristics of of AVE AVE trains trains classesclasses 102 102–112–112 are are summarized summarized in Table in Table 1. The1. The traction traction performanceperformance curve curve (by (by the the eight eight motors) motors) of of AVE AVE trainstrains classes 102 102–112–112 is isshown shown in Figure in Figure 1. 1.

250

200

150

100 Tractive effort (kN) effort Tractive

50

0 0 50 100 150 200 250 300 350 speed (km/h)

FigureFigure 1. 1.Traction Traction performance performance curve of of AVE AVE trains trains classes classes 102 102–112.–112.

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Table 1. Characteristics of AVE trains classes 102–112. Energies 2018, 11, x FOR PEER REVIEW 3 of 17 Power 8000 kW TableVoltage–frequency 1. Characteristics of AVE trains 25 kV–50 classes Hz 102–112. Number of motors 8 No loadPower mass 8000 322 kW t VoltageLength–frequency 25 kV 200–50 m Hz MaximumNumber of speed motors 3308 km/h NumberNo load of seatsmass 322 353 t NumberLength of axes 200 21 m Maximum speed 330 km/h 3. Used in AVE TrainsNumber of seats 353 Number of axes 21 The nominal data of IM implemented in the above trains are given in Table2. More information about3. this Induction motor Motor can be Used found in inAVE the Trains Appendix A. The IMThe has nominal been simulated data of IM by implemented the finite element in the method. above trains The are losses given and in efficiency Table 2. have More been evaluatedinformation through about a completethis motor equivalentcan be found circuit.in the appendix. The results obtained in this analysis have been comparedThe with IM thehas databeen providedsimulated by the the finite manufacturer element method. which The confirm losses theand validity efficiency of have the proposedbeen method.evaluated In addition, through the a methodcompleteused equivalent for the circuit. calculation The results of mechanical obtained and in this iron analysis losses havecan be been applied subsequentlycompared to with the the proposed data provided PMSM by analysis. the manufacturer which confirm the validity of the proposed method. In addition, the method used for the calculation of mechanical and iron losses can be applied subsequently to theTable proposed 2. Nominal PMSMdata analysis. of the induction motor.

Table 2. PowerNominal data of the induction 1020 kW motor. VoltagePower 102 21830 kW V CurrentVoltage 2183 312 V A Torque 3765 N·m Current 312 A Number of poles 4 Torque 3765 N∙m Speed 2590 r/min FrequencyNumber of poles 874 Hz Speed 2590 r/min Frequency 87 Hz 3.1. Finite Element Simulation Load3.1. Finite and Element no-load Simulation operations of the motor was simulated. Figure2 shows the results of no-load flux line distributionLoad and no- andload Figureoperations3 illustrates of the motor air was gap simulated. induction. Figure Static 2 torqueshows the was results obtained of no- fromload the load simulationsflux line distribution at a rated and current Figure in3 illustrates the stator air and gap in induction. the rotor Static for different torque was rotor obtained positions from as the shown in Figureload4 simulations. at a rated current in the stator and in the rotor for different rotor positions as Theshown results in Figure shown 4. in these simulations have been compared with those provided by the motor The results shown in these simulations have been compared with those provided by the motor manufacturer which confirms the good behavior of the simulation model. The values of the air gap manufacturer which confirms the good behavior of the simulation model. The values of the air gap flux and the flux density are suitable for the type of magnetic sheet used. The values of the static flux and the flux density are suitable for the type of magnetic sheet used. The values of the static torquetorque meet meet the requirementsthe requirements of of torque torque necessary necessary forfor the train’s train’s traction traction curve. curve.

Figure 2. Finite element simulation: IM results (Air gap flux per pole = 0.04305 Wb). Figure 2. Finite element simulation: IM results (Air gap flux per pole = 0.04305 Wb).

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Flux densityFlux(T) Flux densityFlux(T)

Length (mm) Length (mm) Figure 3. Finite element simulation: IM results (Air gap flux density, max. value ≈ 0.8≈ T). FigureFigure 3. Finite 3. Finite element element simulation: simulation: IM IM resultsresults (Air gap gap flux flux density, density, max. max. value value ≈ 0.8 T).0.8 T). 8000 8000 6000 6000 4000 4000

2000 m)

∙ 2000 m) ∙ 0 0 20 40 60 80 100 120 140 160 180 0 -2000 0 20 40 60 80 100 120 140 160 180

Static Torque (N Torque Static -2000

Static Torque (N Torque Static -4000 -4000 -6000 -6000 -8000 -8000 Position (º) Position (º) Figure 4. Finite element simulation: IM results (Static torque, rms value = 4155 N∙m). FigureFigure 4. Finite 4. Finit elemente element simulation: simulation: IMIM results (Static (Static torque, torque, rms rms value value = 4155 = 4155 N∙m). N ·m). 3.2. Calculation of Mechanical and Iron Losses 3.2. Calculation of Mechanical and Iron Losses 3.2. CalculationMechanical of Mechanical losses can and be Iron divided Losses into bearing and ventilation losses, which are directly proportionalMechanical to the losses speed can of bethe dividedmachine. into Accura bearingte determination and ventilation of such losses, losses which is a complex are directly task, Mechanicalproportionalbut certain empiricalto losses the speed can expressions of be the divided machine. can into provide Accura bearing te satisfactory determination and ventilation approximations. of such losses losses, Theseis whicha complex expressions are task, directly proportionalbutinclude certain coefficients to the empirical speed that expressions ofvary the with machine. machine can provide Accurate type, size, satisfactory determination ventilation approximations. system, of such etc. losses These is expressionsa complex task, but certainincludeBased empirical coefficients on the expressions that vary with in can [11 machine provide], the bearing type, satisfactory size,losses ventilation (P approximations.c) can be system, calculated etc.These from: expressions include coefficientsBased that on vary the expressions with machine in [11 type,], the size, bearing ventilation losses (P system,c) can be calculated etc. from: N P=kdn  3 Based on the expressions in [11], thecccc bearing lossesN (Pc) can be calculated from: (1) P=kdn1000 3 cccc  (1)  1000  where N is the speed (rpm), dc is the axis diameterN (cm), 3nc is the number of bearings, and kc is the Pc = kc × × dc × nc (1) wherecoefficient N is depending the speed (rpm),on motor dc istype the (betwee axis diametern 0.021000 and (cm), 0.2). nc is the number of bearings, and kc is the coefficientVentilation depending losses on (P ventmotor) are type calculated (betwee byn the0.02 following and 0.2). expression: where NVentilation is the speed losses (rpm), (Pvent d)c areis thecalculated axis diameter by the following (cm), n cexpression:is the number of bearings, and kc is the 1 coefficient depending on motor type (between 0.02 and 0.2).ex p Ppvv en tairx 1 (2) Ppv k ex p Ventilation losses (Pvent) are calculatedv en by tairx thev en t following expression: (2) k v en t with: with: 1 exp Pvent = ·pair·vx (2) k  DNv v  vent x  DN (3) 60v v x  (3) with: 60 πD N where pair is the dissipation loss (W), vx vis the= fanv tangential speed (m/s), Dv is the fan outer (3) air x x v wherediameter p (m), is the kvent dissipation is the coefficient loss (W depending), v is the onfan60 motor tangential type speedand ventilation (m/s), D systemis the fan (between outer diameter (m), kvent is the coefficient depending on motor type and ventilation system (between where pair is the dissipation loss (W), vx is the fan tangential speed (m/s), Dv is the fan outer diameter (m), k vent is the coefficient depending on motor type and ventilation system (between 15,000 and

150,000), and exp is the coefficient depending on motor type and ventilation system (between 2 and 3). Energies 2018, 11, x FOR PEER REVIEW 5 of 17 Energies 2018, 11, 1549 5 of 17 15,000 and 150,000), and exp is the coefficient depending on motor type and ventilation system (between 2 and 3). Due to the computational complexity, dissipation losses can be calculated from the output power Due to the computational complexity, dissipation losses can be calculated from the output and estimated efficiency of the motor during operation. power and estimated efficiency of the motor during operation. MechanicalMechanical losses losses obtained obtained from manufacturer from manufacturer tests were tests compared were compared with the results with the of Equations results of (1)–(3) as shownEquations in Figure (1)–(3)5 as, whereshown anin Figure excellent 5, where fit was an excellent verified fit between was verified the analytical between the results analytical and the experimentalresults and tests the experimental by manufacturer. tests by manufacturer.

calculation measure 5000

4500

4000

(W) 3500

3000

2500

2000

Mechanical lossesMechanical 1500

1000

500

0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Speed (r/min) FigureFigure 5. Mechanical 5. Mechanical losses losses obtained obtained by manufacturer tests tests and and analytical analytical calculation. calculation.

Iron losses can be approximately calculated by Steinmetz equations [12]. These equations can beIron used losses in the can presence be approximately of sinusoidal or calculated low harmonic by Steinmetzwaveforms. equationsSince the measurements [12]. These of equations the can bemanufacturer used in the laboratory presence tests of sinusoidal were made or lowunder harmonic sinusoidal waveforms. excitation, SteinmetzSince the measurementsequations’ of thepara manufacturermeters were fitted laboratory to obtain tests the were analytical made results under of sinusoidal losses, which excitation, were then Steinmetz compared equations’ with parametersexperimental were measurements. fitted to obtain the analytical results of losses, which were then compared with experimentalHysteresis measurements. losses (Phis) were calculated by Steinmetz equation: Hysteresis losses (Phis) were calculated by Steinmetzik equation: P( W / k g )kfB1 0 an2  h ishim ax i  (4) i1i=k P (W/kg) = k ·fa·Bn ·10−2 (4) where kh is the loss constant of thehis material (between∑ h 2 andi maxi5), a is the frequency exponent (between i=1 1 and 1.2), and n is the induction exponent (between 1.8 and 2). Equation (4) was separately applied to different regions of the motor, i.e., stator yoke, rotor where kh is the loss constant of the material (between 2 and 5), a is the frequency exponent (between 1 and 1.2),yoke, and stator n isteeth the induction and rotor teeth. exponent In these (between regions 1.8 the and induction 2). was estimated by finite element simulation. Total losses were obtained by multiplying the specific losses (W/kg) by the weight of Equation (4) was separately applied to different regions of the motor, i.e., stator yoke, rotor iron in each region. yoke, stator teeth and rotor teeth. In these regions the induction was estimated by finite element Eddy current losses (Pfou) were calculated by the following Steinmetz equation: simulation. Total losses were obtained by multiplying the specific losses (W/kg) by the weight of iron ik in each region. P (W/kg) k  fx  e y  B z  10 2 fo u f i m ax i (5) Eddy current losses (Pfou) were calculatedi1 by the following Steinmetz equation:

where kf is the loss constant of the material (betweeni=k 10 and 100), e is the sheet thickness (m), and x, y, z are the exponents eddy current losses (between 2 andx y2.2).z 2 Pfou(W/kg) = ∑ kf·fi ·e ·Bmaxi·10 (5) The material of the electrical steel used ini =manufacturing1 of the induction motor is the M-19 (nomenclature standard AISI), which corresponds to M290-50A (nomenclature EN10106). This wherematerial kf is the has loss also constant been selected of the in material the finite (between element 10simulatio and 100),ns carried e is the out. sheet The thickness manufacturer (m), andof x, y, z arethe the electrical exponents steel eddy has given current us the losses specific (between losses in 2 andW/kg 2.2). [13] for different flux densities (from 0.1 T toThe 1.5 material T) and for of differentthe electrical frequencies steel used (from in 50 manufacturing Hz to 1000 Hz). of The the adjustment induction of motor the different is the M-19 (nomenclaturecoefficients standard corresponding AISI), to which the Steinmetz corresponds equations to M290-50A was made (nomenclature by comparing EN10106). the results This of thematerial has alsoestablished been selected model with in the the finite specific element losses simulationsdata of the electrical carried steel out. provided The manufacturer by the manufacturer. of the electrical steelThe has different given us coefficients the specific selected losses from in this W/kg adjustment [13] for and different applied fluxin Eq densitiesuations (4) (from and (5) 0.1 are: T k toh = 1.5 T) and for different frequencies (from 50 Hz to 1000 Hz). The adjustment of the different coefficients corresponding to the Steinmetz equations was made by comparing the results of the established model with the specific losses data of the electrical steel provided by the manufacturer. The different coefficients selected from this adjustment and applied in Equations (4) and (5) are: kh = 4.8, a = 1.2, Energies 2018, 11, 1549 6 of 17

n = 2Energies for hysteresis 2018, 11, x FOR losses PEER in REVIEW Equation (4), and kf = 60, e = 0.0005 m, x = 2.05, y = 2, z = 2.056 of for 17 eddy current losses in Equation (5). 4.8,The a procedure = 1.2, n = 2 for hysteresis calculation losses of hysteresis in Equation losses (4), and in k thef = 60, four e = tested 0.0005regions m, x = 2.05, was y also= 2, z followed = 2.05 to quantifyfor eddy thetotal current iron losses losses in asEquation the sum (5). of hysteresis losses and eddy current losses. Figure6 compares the resultsThe of procedure the manufacturer for calculation tests of with hysteresis the results losses in obtained the four fromtested applyingregions was analytical also followed methods to quantify the total iron losses as the sum of hysteresis losses and eddy current losses. Figure 6 using the Equations (4) and (5), for a 50 Hz frequency as a function of the estimated air gap flux compares the results of the manufacturer tests with the results obtained from applying analytical density. There were differences between the analytical calculations and the experimental measurements, methods using the Equations (4) and (5), for a 50 Hz frequency as a function of the estimated air especiallygap flux with density. high fluxThere density were differences values. However, between theythe analytical were not calculations significant, and so we the could experimental consider the analyticalmeasurements, procedure especially satisfactory. with high flux density values. However, they were not significant, so we couldAll experimental consider the analytical measure procedure tests carried satisfactory. out by the motor manufacturer and by the motor user have beenAll made experimental in accordance measure with tests international carried out by standards the motor IEC manufacturer 60034-2-1 and [14 ]by and the IEC motor 60349-2 user [15], so thathave losses been are made separated in accordance as per with the standards’international indications standards IEC into 60034 copper-2-1 losses, [14] and iron IEC losses, 60349- mechanical2 [15], lossesso and that stray losses load are losses. separated as per the standards’ indications into copper losses, iron losses, mechanicalTo obtain thelosses mechanical and stray load losses losses. and the iron losses, shown in Figures5 and6 respectively, To obtain the mechanical losses and the iron losses, shown in Figures 5 and 6 respectively, the the sinusoidal voltage and no-load operation have been applied. The measuring equipment used sinusoidal voltage and no-load operation have been applied. The measuring equipment used consists of a 3-phase electronic wattmeter (which allows the measurement of voltage, current, power consists of a 3-phase electronic wattmeter (which allows the measurement of voltage, current, and powerpower andfactor), power an factor),analogical an analogical torque-meter torque on-meter the axis, on the and axis, a digital and a transducer digital transducer for measuring for speed.measuring The motor speed. was The in motor service was for in 30 service min beforefor 30 min taking before the taking measurements, the measurements, to achieve to achieve the proper behaviorthe proper of the behavior bearings of to the correctly bearings determineto correctly thedetermine mechanical the mechanical losses. losses.

FigureFigure 6. Iron 6. Iron losses losses obtained obtained by by manufacturer manufacturer tests tests and and analytical analytical calculation calculation (f = 50 (f =Hz). 50 Hz).

To obtain the output power and performance, two identical motors have been mechanically coupledTo obtain (back the-to output-back method). power and The performance,same measuring two equipment identical indicated motors above have were been used. mechanically The coupledmeasurement (back-to-back of the method). torque and The the speed same, measuring together with equipment the measurements indicated of above the electronic were used. The measurementwattmeter, allowed of the the torque determination and the of speed, the output together power with and the the measurements efficiency of the of motor.the electronic A wattmeter,temperature allowed of 150 the °C was determination considered as of the the reference output temperature power and to calculate the efficiency the stator of copper the motor. A temperaturelosses. of 150 ◦C was considered as the reference temperature to calculate the stator copper losses. 3.3. Analysis of the Equivalent Circuit 3.3. AnalysisSince of losses the Equivalent have a strong Circuit influence on motor efficiency, the circuit in [16] was considered as theSince equivalent losses have circuit a strongshown in influence Figure 7. on The motor considered efficiency, equivalent the circuit circuit in parameters [16] was consideredare: R1, stator as the resistance; R’2, rotor resistance referred to the stator; Xd1, leakage reactance of the stator; X’d2, rotor equivalent circuit shown in Figure7. The considered equivalent circuit parameters are: R 1, stator leakage reactance referred to the stator; Xμ, magnetizing reactance; RFe , iron loss resistance; s, slip; resistance; R’2, rotor resistance referred to the stator; X , leakage reactance of the stator; X’ , rotor Rfreg, mechanical loss resistance; Rad, stray load loss resistance;d1 Rload, load resistance. d2 leakage reactanceThe main referred parameters to the of stator; the equivalent Xµ, magnetizing circuit are reactance; included in R Fe Table, iron 3. loss Mechanical resistance; loss s, slip; Rfreg,resistance mechanical (Rfreg loss), iron resistance; loss resistance Rad, stray(RFe), loadstray lossload resistance; loss resistance Rload (R,ad load) and resistance. load resistance (Rload) wereThe maincalculated parameters as specified of the in equivalent[17], where this circuit equivalent are included circuit was in Table satisfactorily3. Mechanical used in loss a railway resistance (Rfreg ), iron loss resistance (RFe), stray load loss resistance (Rad) and load resistance (Rload) were Energies 2018, 11, 1549 7 of 17 calculatedEnergies 2018 as specified, 11, x FOR PEER in [REVIEW17], where this equivalent circuit was satisfactorily used in7 a of railway 17 Energies 2018, 11, x FOR PEER REVIEW 7 of 17 traction motor. The evolution of mechanical losses in Figure5 and iron losses in Figure6 was used traction motor. The evolution of mechanical losses in Figure 5 and iron losses in Figure 6 was used to fittraction resistances motor. R The andevolution R , respectively.of mechanical losses Additionally, in Figure the5 and saturation iron losses effect in Figure was 6 considered was used on to fit resistancesfreg Rfreg and RFeFe, respectively. Additionally, the saturation effect was considered on the the magnetizingmagnetizingto fit resistances inductance Rfreg and valueR valueFe, respectively. (Figure (Figure 8)8 Additionally,) and and the the variation variation the saturation of of rotor rotor parameterseffect parameters was considered with with slip slipon (s), the as (s), as proposedproposedmagnetizing in [18 in]. [18]. inductance value (Figure 8) and the variation of rotor parameters with slip (s), as proposed in [18].

FigureFigure 7. Induction7. Induction motor motor equivalentequivalent circuit circuit including including all alllosses. losses. Figure 7. Induction motor equivalent circuit including all losses. 45 45 40 40

35 (mH)

μ 35

(mH) 30 μ 30 25 25 20 20 15 15

Magnetizing inductance , L , inductance Magnetizing 10

Magnetizing inductance , L , inductance Magnetizing 10 5 5 0 0 0 5 10 15 20 25 30 35 40 45 50 0 5 10 15 20 25 30 35 40 45 50 Air gap flux (mWb) Air gap flux (mWb) Figure 8. Magnetizing inductance evolution with air gap flux. FigureFigure 8. 8Magnetizing. Magnetizing inductanceinductance evolution evolution with with air air gap gap flux. flux. Table 3. Equivalent circuit parameters under rated conditions. Table 3. Equivalent circuit parameters under rated conditions. Table 3. Equivalent circuitR1 parameters0.0445 under Ω rated conditions. R1 0.0445 Ω R’2 0.0406 Ω R’2 0.0406 Ω RLd11 0.04450.00102Ω H Ld1 0.00102 H R’L’d22 0.04060.00082Ω H LL’d2 0.001020.00082 H H Ld1μ 0.03013 H L’Ld2μ 0.000820.03013 H H L 0.03013 H The analytical results of output powerµ and efficiency of the equivalent circuit at different frequenciesThe analytical and those results obtained of output in the tests power were and compared efficiency in of Fi gures the equivalent 9 and 10, circuitrespectively. at different Good frequencies and those obtained in the tests were compared in Figures 9 and 10, respectively. Good Theresults analytical can be observed results of in theoutput calculation power of and the efficiency efficiency, of with the only equivalent small differences circuit at in different the results can be observed in the calculation of the efficiency, with only small differences in the frequenciesoperation and at low those frequencies obtained are in appreciated. the tests were compared in Figures9 and 10, respectively. Good operation at low frequencies are appreciated. results can be observed in the calculation of the efficiency, with only small differences in the operation at low frequencies are appreciated.

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Figure 9. Output power at different operation frequencies. FigureFigure 9. Output9. Output power power at at differentdifferent operation frequencies. frequencies.

Figure 9. Output power at different operation frequencies.

Figure 10. Efficiency at different operation frequencies. FigureFigure 10. 10.Efficiency Efficiency at at different different operation frequencies. frequencies. 4. Structures of Permanent Magnet Synchronous Motors (PMSM) Proposed 4. Structures of Permanent Magnet Synchronous Motors (PMSM) Proposed 4. StructuresTo evaluate of Permanent the possibilityFigure Magnet 10.of SynchronousreplacingEfficiency atthe different IM Motors by operationa PMSM, (PMSM) frequencies. three Proposed magnet structures of the rotor To evaluate the possibility of replacing the IM by a PMSM, three magnet structures of the rotor were proposed for the PMSMs [19,20], as shown in Figure 11: To4.were Structures evaluate proposed theof forPermanent possibility the PMSMs Magnet of [19,20], replacing Synchronous as shown the IM in Motors byFigure a PMSM, (PMSM)11: three Proposed magnet structures of the rotor were proposed- surface for magnets the PMSMs (SPM) [19,20], as shown in Figure 11: - Tosurface evaluate magnets the possibility (SPM) of replacing the IM by a PMSM, three magnet structures of the rotor - interior magnets with radial magnetization (RM-IPM) were- interiorproposed magnets for the withPMSMs radial [19,20], magnetization as shown in(RM Figure-IPM) 11: - surface- interior magnets magnets (SPM) with tangential magnetization (TM-IPM) - interior magnets with tangential magnetization (TM-IPM) - -interior surface magnets magnets with (SPM) radial magnetization (RM-IPM) - -interior interior magnets magnets with with tangential radial magnetization magnetization (RM- (TM-IPM)IPM) - interior magnets with tangential magnetization (TM-IPM)

(a) (b) (c) (a) (b) (c) Figure 11. PMSM rotor structures: (a) Surface magnets (SPM); (b) Interior magnets with radial Figure 11. PMSM rotor structures: (a) Surface magnets (SPM); (b) Interior magnets with radial magnetization (RM-IPM); (c) Interior magnets with tangential magnetization (TM-IPM). magnetization (RM-IPM);(a )( c) Interior magnets with(b) tangential magnetization(c) (TM-IPM).

FigureThe same 11. PMSMstator used rotor structures:in the IM was (a) Surface selected magnets for the (SPM); above ( brotor) Interior structures magnets to withcompare radial them FigureThe 11. samePMSM stator rotor used structures: in the IM (awas) Surface selected magnets for the (SPM);above rotor (b) Interior structures magnets to compare with radialthem withmagnetization the current IM, (RM especially-IPM); (c) Interior in terms magnets of electromagnetic with tangential performancemagnetization (TMand -IPM).efficiency. The use of with the current IM, especially in terms of electromagnetic performance and efficiency. The use of magnetizationthe same stator (RM-IPM); initially resulted (c) Interior in fewer magnets changes with tangentialin the manufacturing magnetization process (TM-IPM). of the new motor the same stator initially resulted in fewer changes in the manufacturing process of the new motor and Thein the same power stator electronics used in requiredthe IM was for selectedmotor control. for the It above is important rotor structures to note that to comparemodifying them the and in the power electronics required for motor control. It is important to note that modifying the Thewith samethe current stator IM, used especially in the IM in wasterms selected of electromagnetic for the above performance rotor structures and efficiency. to compare The use them of with the currentthe same IM, stator especially initially in resulted terms of in electromagnetic fewer changes in performance the manufacturing and efficiency. process of The the usenew ofmotor the same statorand initially in the resultedpower electronics in fewer required changes for in motor the manufacturing control. It is important process to of note the that new modifying motor and the in the

Energies 2018, 11, 1549 9 of 17 power electronics required for motor control. It is important to note that modifying the winding by increasing the number of poles, using a concentrated winding with a fractional number of slots per pole and phase [21] could improve PMSM performance.

TheEnergies selection 2018, 11, x ofFOR the PEER same REVIEW stator in the proposed designs of the PMSM that in the IM9 currently of 17 used is due to the assumption of non-aggressive modification of the manufacturing process and the powerwinding electronics by increasing installed, the conditions number of prefixedpoles, using by a the concentrated manufacturer winding and with the currenta fractional customer number of the motors.of slots Therefore, per pole theand usephase of [21] the could same improve stator has PMSM been performance. prioritized in the design over an optimized motor design,The selection which could of the improvesame stator some in the aspects proposed of operation designs of if the an PMSM optimization that in the algorithm IM currently has been appliedused [22 is– due24]. to the assumption of non-aggressive modification of the manufacturing process and the power electronics installed, conditions prefixed by the manufacturer and the current customer of The selected magnet was a rare-earth magnet, NdFeB (ND-35UH type), with the following main the motors. Therefore,◦ the use of the same stator has been prioritized in the design over an characteristicsoptimized at motor 26 C: design, which could improve some aspects of operation if an optimization - algorithmRemanent has induction been applied = 1.2 [22 T–24]. The selected magnet was a rare-earth magnet, NdFeB (ND-35UH type), with the following - Coercitive field = −905 kA/m main characteristics at 26 °C: - Relative permeability = 1.055 - Remanent induction = 1.2 T The- magnetsCoercitive werefield = approximately −905 kA/m dimensioned in width to roughly cover the pole arc of the machine- andRelative in length permeability (Lm) from = 1.055 Equation (6) [19]: The magnets were approximately dimensioned in width to roughly cover the pole arc of the Bg lg machine and in length (Lm) from EquationL m(6)≈ [11.29]: (6) µ0 Hm Blgg L1m .2 (6) where Bg is the air gap induction, lg is the air gap length, H and Hm is the magnet’s magnetic field at the 0m operating point. where Bg is the air gap induction, lg is the air gap length, and Hm is the magnet’s at In order to avoid demagnetization problems of magnet, Hm was given a value corresponding to a the operating point. 0.6 Br according to the magnet characteristic, where Br is the remanent induction. In order to avoid demagnetization problems of magnet, Hm was given a value corresponding 4.1. Finiteto a 0.6 Element Br accordi Simulationng to the magnet characteristic, where Br is the remanent induction. Load4.1. Finite and Element no-load Simulation simulations of the PMSM rotor structures were conducted. Figures 12 and 13 summarizeLoad the and results no-load of thesimulations no-load of flux the linePMSM distribution, rotor structures whereas were conducted. Figures 14 Figuresand 15 12 illustrate and 13 the air gapsummarize induction the waveforms. results of the Theno-load back flux electromotive line distribution, force whe (EMF)reas Figures obtained 14 and in the 15 illustrate three structures the was 6.89air gap Vs/rad induction in the waveforms. SPM, 5.32 The Vs/rad back in electromotive the RM-IPM force and (EMF) 5.31 Vs/rad obtained in in the the TM-IPM, three structures respectively. Staticwas torque 6.89 Vs/rad was obtained in the SPM, from 5.32 load Vs/rad simulations in the RM- atIPM rated and 5.31 current Vs/rad and in forthe differentTM-IPM, respectively. rotor positions, as shownStatic intorque Figure was 16 obta[25].ined from load simulations at rated current and for different rotor positions, Itas wasshown remarkable in Figure 16 that [25]. an air gap flux per pole obtained in surface magnets structure was higher It was remarkable that an air gap flux per pole obtained in surface magnets structure was than the interior magnets structures. Also, in the three cases of PMSM, the air gap flux density was higher than the interior magnets structures. Also, in the three cases of PMSM, the air gap flux higher than that obtained in the IM (Figure2). density was higher than that obtained in the IM (Figure 2).

Figure 12. Finite element simulation: SPM results (Air gap flux per pole = 0.06371 Wb). Figure 12. Finite element simulation: SPM results (Air gap flux per pole = 0.06371 Wb).

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Energies 2018, 11, 1549 10 of 17

Energies 2018, 11, x FOR PEER REVIEW 10 of 17

((aa)) (a) (b) ((bb)) Figure 13. Finite element simulation: IPM results: (a) RM-IPM (Air gap flux per pole = 0.04905 Wb); FigureFigure 13. Finite 13. Finite element element simulation: simulation: IPM IPM results: results: ( (aa) RM-IPMRM-IPM (Air (Air gap gap flux flux per per pole pole = 0.04905 = 0.04905 Wb); Wb); Figure 13. (bFinite) TM-IPM element (Air gap simulation: flux per pole IPM = 0.05946 results: Wb). (a) RM-IPM (Air gap flux per pole = 0.04905 Wb);

((bb)) TMTM(b)--IPMIPM TM-IPM (Air(Air (Air gapgap gap fluxflux flux perper per polepole pole == 0.05946 =0.05946 0.05946 Wb).Wb). Wb).

Flux densityFlux(T)

Flux densityFlux(T) Flux densityFlux(T)

Length (mm) Figure 14. Finite element simulation: SPM results (Air gap flux density; max. value ≈ 1 T).

Length (mm) Length (mm)

FigureFigureFigure 14.14. Finite 14.FiniteFinite elementelement element simulation:simulation: simulation: SPMSPM SPM resultsresults (Air(Air gap gapgap flux fluxflux density; density;density; max. max.max. value valuevalue≈ 1 ≈≈ T). 11 T).T).

Fluxdensity(T) Fluxdensity(T)

Length (mm) Length (mm)

(a) (b)

Fluxdensity(T)

Fluxdensity(T)

Fluxdensity(T) Fluxdensity(T) Figure 15. Finite element simulation: IPM results: (a) RM-IPM (Air gap flux density; max. value ≈ 0.8T); (b) TM-IPM (Air gap flux density; max. value ≈ 0.7 T).

LengthLength (mm) (mm) Length (mm) Length (mm) ((aa)) ((bb)) Figure 15. Finite element simulation: IPM results: (a) RM-IPM (Air gap flux density; max. value ≈ FigureFigure 15. Finite 15. Finite element element simulation: simulation: IPMIPM results: results: (a )( RM-IPMa) RM-IPM (Air gap(Air flux gap density; flux density; max. value max.≈ 0.8T); value ≈ 0.8T);0.8T);( b ((b)b TM-IPM)) TMTM--IPMIPM (Air (Air(Air gap gapgap flux flux density;flux density;density; max. valuemax.max. ≈ valuevalue0.7 T). ≈≈ 0.70.7 T).T).

Energies 2018, 11, 1549 11 of 17 Energies 2018, 11, x FOR PEER REVIEW 11 of 17

SPM RM-IPM TM-IPM 8000

6000

4000 m) ∙ 2000

0 0 20 40 60 80 100 120 140 160 180

-2000 Static Torque (N Torque Static

-4000

-6000

-8000 Position (º)

Figure 16 16.. FiniteFinite element element simulation: simulation: static torque static results torque (rms results value (rmss: SPM values: = 4109SPM N∙m; = RM 4109-IPM N·m; = 3320RM-IPM N∙m; = TM 3320-IPM N·m; = 3159 TM-IPM N∙m). = 3159 N·m).

From the simulations shown in Figures 14 and 15, the SPM rotor structure provided an From the simulations shown in Figures 14 and 15, the SPM rotor structure provided an evolution evolution of air gap flux density which was more sinusoidal than with the structures of interior of air gap flux density which was more sinusoidal than with the structures of interior magnets. magnets. Consequently, the harmonic content of this waveform would be lower in the SPM. Consequently, the harmonic content of this waveform would be lower in the SPM. It was also observed in Figure 16 that the static torque values obtained from SPM rotor It was also observed in Figure 16 that the static torque values obtained from SPM rotor structure structure were higher, so this structure would be better adapted to study the needs of the railway were higher, so this structure would be better adapted to study the needs of the railway application. application. Furthermore, by comparing the static torque results obtained from Figure 16 with IM results Furthermore, by comparing the static torque results obtained from Figure 16 with IM results from Figure4, the evolution of the static torque for the different rotor positions has a more sinusoidal from Figure 4, the evolution of the static torque for the different rotor positions has a more distribution in the SPM. sinusoidal distribution in the SPM. 4.2. Inductances and Losses 4.2. Inductances and Losses In order to calculate the efficiency of the three PMSM rotor structures, a full power balance wasIn performed order to by calculate considering the efficiency the same of stator the three as that PMSM used rotor for the structures, IM in Section a full3 power, so the balance stator wasresistances performed had the by same considering value. The the inductances same stator were as that obtained used by for finite the IM element in Section simulation 3, so by the exciting stator resistancesa stator phase had and the replacing same value. the rotor The inductances magnets with were air (since obtained the simulation by finite element was conducted simulation using by excitingdemagnetized a stator magnets, phase their and permeability replacing the value rotor is magnets very close with to air). air (since Two simulations the simulation had to was be conductedcarried out to using determine demagnetized the direct magnets, and quadrature their permeabilityaxis inductances value with is respect very closeto the toexcited air). stator Two simulations had to be carried out to determine the direct and quadrature axis inductances with phase. The end coil inductances (Lcb) were determined by analytical calculation using the following respectequation to [ 26 the]: excited stator phase. The end coil inductances (Lcb) were determined by analytical calculation using the following equation [26]: 2 µ A2 2Nf 0 p Lcb ≈ kcb 2 (7) pn 2 πAArs 2Npff 0p Lkc b c b (7) where N is the number of turns per phase, p is thep n number A of pole pairs, n is the number of slots f p f rs pf per pole and per phase, Ap is the pole width, Ars is the stator slot width and kcb is the dimensionless whereoverhang Nf is factor the number (between of 0.5 turns and per 1). phase, p is the number of pole pairs, npf is the number of slots per poleThe and final per inductance phase, A valuesp is the are pole given width, inTable Ars is4 .the The stator effect slot of magneticwidth and saturation kcb is the wasdimensionless negligible overhangat different factor stator (between currents 0.5 due and to 1). the effect of low relative permeability of the magnets, which was consideredThe final in the inductance magnetic valuesequivalent are circuit given analysis. in Table It 4. can The be effect seen that of magneticthe direct and saturation quadrature was negligibleaxis inductances at different in the stator SPM structurecurrents due were to same, the effect whereas of low they relative were not permeability same in the of IPM the structures, magnets, whichas in the was case considered of salient in pole the machines. magnetic equivalent circuit analysis. It can be seen that the direct and quadrature axis inductances in the SPM structure were same, whereas they were not same in the IPM structures, as in the case of salient pole machines.

Energies 2018, 11, 1549 12 of 17

Table 4. Inductances.

Energies 2018, 11, x FOR PEER REVIEW Single Direct Axis Quadrature Axis 12 of 17 L (mH) Ld (mH) Lq (mH) SPM 4.72 Table 4. Inductances. RM-IPM 9.12 6.38 Single Direct Axis Quadrature Axis TM-IPM 8.87 15.85 L (mH) Ld (mH) Lq (mH) SPM 4.72 All losses were determinedRM-IPM as follows: 9.12 6.38 TM-IPM 8.87 15.85 - Stator Joule losses: with the same resistance value as in the IM. - MechanicalAll losses losses: were determined using Equations as follows: (1)–(3) in Section 3.2. - Iron losses [27]: using Equations (4) and (5) and the calculation process in Section 3.2. - Stator Joule losses: with the same resistance value as in the IM. - -Stray Mechanical load losses: losses: following using Equations international (1)–(3) standards in Section IEC3.2. 60034-2-1 [14] and IEC 60349-2 [15]. For- theIron motor losses with [27]: SPMusing rotor Equations structure, (4) and a steady(5) and statethe calculation analysis was process carried in Section out by 3.2. only considering - Stray load losses: following international standards IEC 60034-2-1 [14] and IEC 60349-2 [15]. the synchronous inductance similar to cylindrical rotor synchronous machines. On the other hand, for the motorsFor the with motor IPM with rotor SPM structures, rotor structure, longitudinal a steady and state transversal analysis inductances was carried were out by considered only similarcon tosidering salient the pole synchronous synchronous inductance machines. similar to cylindrical rotor synchronous machines. On the other hand, for the motors with IPM rotor structures, longitudinal and transversal inductances were 5. Performanceconsidered similar of PMSM to salient Compared pole synchronous with Respect machines. to the IM Used

Initially,5. Performance in Section of PMSM3, the Compared performance with ofRespect the IM to currentlythe IM Used used in high speed railway traction was studied. Electromagnetic and functional performances, especially efficiency, were quantified. Initially, in Section 3, the performance of the IM currently used in high speed railway traction Comparisonwas studied. of the Electromagnetic analytical results and functional with motor performances, specifications especially underpin efficiency, the were calculation quantified. process, particularlyCompar inison the of estimation the analytical ofmotor results losses. with motor specifications underpin the calculation process, PMSMsparticularly have in the been estimation postulated of motor as an losses. alternative to traction IMs, especially due to their expected higher efficiencyPMSMs andhave powerbeen postulated density. Threeas an alternative PMSM rotor to traction structures, IMs, oneespecially with surfacedue to their magnets expected and two with interiorhigher efficiency magnets, and were power evaluated density. in Three Section PMSM4. Initially, rotor structures, only slightly one with aggressive surface replacementmagnets and was considered,two with keeping interior the magnets, same stator were structure evaluated (dimensions, in Section 4.windings Initially,... only) to slightly evaluate aggressive the potential improvementsreplacement provided was considered, by the tested keeping PMSM the rotor same structures stator structure [24]. (dimensions, windings…) to evaluate the potential improvements provided by the tested PMSM rotor structures [24]. Figure 17 plots the efficiency for three PMSM rotor structures with the same frequencies and Figure 17 plots the efficiency for three PMSM rotor structures with the same frequencies and output power previously analyzed in the IM. Operating conditions are summarized in AppendixA, output power previously analyzed in the IM. Operating conditions are summarized in Appendix A, FigureFigure A2. TheA2. efficiencyThe efficiency obtained obtained with with the the PMSM PMSM structures structures isis slightlyslightly higherhigher with with respect respect to to the the IM for allIM the for operating all the operating frequencies frequencies of the application, of the application, highlighting highlighting greater differences greater differences for the operation for the at low frequencies.operation at low frequencies.

FigureFigure 17. Efficiency 17. Efficiency at differentat different operation operation frequencies: frequencies: comparative comparative between between the thethree three PMSM PMSM rotor rotor structuresstructures with with respect respect to theto the IM. IM.

Energies 2018, 11, 1549 13 of 17

The most characteristic values in Table5 were compared by using the above analytical procedures [28,29].

Table 5. Comparison of motor performance parameters between IM and PMSM rotor structures.

Air Gap Flux Max. Air Gap Static Nominal Power per Pole Flux Density Torque Efficiency Density (Wb) (T) (N·m) (pu) (kW/kg) IM 0.04305 0.8 4155 0.9651 0.7379 SPM 0.06371 1 4109 0.9674 0.8155 RM-IPM 0.04905 0.8 3320 0.9721 0.7837 TM-IPM 0.05946 0.7 3159 0.9725 0.7868

Air gap flux was higher in all PMSM rotor structures than the IM, especially in the SPM. In contrast, static torque in all PMSM rotor structures was lower than the IM, especially in the IPM. Nominal efficiency of all PMSM rotor structures was higher than the IM, although this improvement is not very important because motor power and application type had a strong impact on energy consumption. Power density was only slightly higher in all PMSM rotor structures than in the IM, so, it was preferred to compare efficiency for the same output power at selected operating points analyzed for different frequencies. As discussed earlier, redesigning the specific stator for the PMSM rotor structures by using a larger number of poles would result in increased power density. Finally, a comparative study of manufacturing materials costs was conducted for the four motors in collaboration with some specialist companies located in Catalonia. The weight of the motor parts was calculated and the following approximate prices were used: - Magnetic sheet: 0.98 €/kg - Copper: 7.57 €/kg - Neodymium magnet: 133.62 €/kg - Steel for the axis: 2.32 €/kg - Aluminum for the frame: 1.49 €/kg The following costs were obtained from the weights and unit price of materials: - Induction motor: 2953 € - Permanent magnet synchronous motor, SPM rotor structure: 6472 € - Permanent magnet synchronous motor, RM-IPM rotor structure: 6089 € - Permanent magnet synchronous motor, TM-IPM rotor structure: 4820 € Similarly, the energy consumption for a 6000 h/year operation at several operating points (according Figures1 and A2) was estimated for the PMSM rotor structures. Annual energy and financial savings were associated with energy savings (for an estimated cost of 0.07 €/kWh) over the IM. Also, the materials cost increased for an expected amortization period and environmental impact of energy savings were calculated exclusively in terms of reduction of equivalent CO2 emission (for a 0.6 kg CO2/kWh ratio) [30,31]. These results are summarized in Table6.

Table 6. Savings, amortization of materials and CO2 emission reduction of PMSM structures compared to IM.

Annual Energy Annual Financial Amortization Annual CO2 Savings Savings of Materials Emission Reduction (kWh) (€) (days) (kg) SPM 18,628 1304 986 11,177 RM-IPM 47,250 3307 347 28,350 TM-IPM 52,634 3684 187 31,580 Energies 2018, 11, 1549 14 of 17

Energies 2018, 11, x FOR PEER REVIEW 14 of 17 To achieve good motor reliability, an important feature for railway applications, the following maintenanceTo achieve operations good aremotor carried reliability, out onan theimportant currently feature used for IM: railway tightness applications, test, cooling the following air control, checkingmaintenance of the motor operations cables, are checkingcarried out of on the the sensors, currently maintenance used IM: tightness and lubricationtest, cooling ofair the contr bearings,ol, revisionchecking and cleaningof the motor of thecables, bearings, checking external of the sensors, and internal maintenance cleaning and oflubrication the motor, of the and bearings, control and measurementrevision and of thecleaning insulation of the bearings, (in service external and afterand internal cleaning cleaning and drying). of the motor, The totaland control revision and of the previousmeasurement aspects is of carried the insulation out in cycles (in service of 5 years,and after and cleaning lubrication and drying). of the bearings The total must revision be doneof the every 350,000previous km. Fromaspects the is above,carried out it is in observed cycles of that5 years, the and most lubrication demanding of the parts bearings of the must motor be done in terms of maintenanceevery 350,000 and km. reliability From the areabove, bearings it is observed and stator that windings. the most demanding With the premise parts of thatthe motor maintaining in terms of maintenance and reliability are bearings and stator windings. With the premise that the same stator in the proposed PMSM than in the IM currently used, we can say that there will be maintaining the same stator in the proposed PMSM than in the IM currently used, we can say that no appreciable changes in terms of maintenance needs and motor reliability. An aspect that would there will be no appreciable changes in terms of maintenance needs and motor reliability. An aspect increasethat thewould fault increase tolerance the fault of motors tolerance in of traction motors applications in traction applications refers to therefers increase to the increase in the numberin the of statornumber phases, of a stator design phases, aspect a thatdesign would aspect equally that would affect equally the IM affect and thethe PMSMIM and motorsthe PMSM [32 ].motors [32]. 6. Conclusions 6. Conclusions The results obtained in the study showed that the PMSM rotor structures offer higher efficiency than the IM.The Despite results obtai not beingned in significant, the study showed this increase that the has PMSM an interesting rotor structures influence offer on thehigher annual energyefficiency consumption than the of IM. railway Despite traction. not being The significant, improvement this increase in power has an density interesting was influence small because on the the sameannual stator structure energy consumption was kept, a of hypothesis railway traction. of this study. The improvement Greater improvements in power density could be was achieved small by because the same stator structure was kept, a hypothesis of this study. Greater improvements could redesigning the stator and increasing the number of poles. be achieved by redesigning the stator and increasing the number of poles. The increase in the cost of the materials and the manufacturing process represented that the use The increase in the cost of the materials and the manufacturing process represented that the of theuse PMSM of the as PMSM compared as compared to the IM to can the be IM amortized can be amortized in a relatively in a relatively short time short due time to the due reduction to the in electricalreduction energy in electrical consumption. energy consumption. TheThe good good behavior behavior of of the the analytical analytical calculations calculations used used in in the the IM IM and and compared compared with with test test measurementsmeasurements confirms confirms the validity the validity of the of proposed the proposed method method to calculate to calculate motor motor losses losses and efficiency. and efficiency. Author Contributions: M.T. and J.I.P. proposed the methodology and the calculation procedure; J.A.J. provided the experimentalAuthor Contributions data. : Marcel Torrent and José Ignacio Perat proposed the methodology and the calculation procedure; José Antonio Jiménez provided the experimental data. Funding: This research received no external funding. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflicts of interest. Conflicts of Interest: The authors declare no conflicts of interest. Appendix A Appendix A Construction data of the induction motor implemented in the AVE trains are given in Table A1. Construction data of the induction motor implemented in the AVE trains are given in Table A1. FigureFigure A1 shows A1 shows a picture a picture of theof the motor motor and and its its gearbox.gearbox. The The torque torque-speed-speed and and output output power power-speed-speed characteristicscharacteristics for eachfor each motor motor are are summarized summarizedin in FigureFigure A2..

FigureFigure A1. A1.Motor Motor with gearbox. gearbox.

Energies 2018, 11, 1549 15 of 17 Energies 2018, 11, x FOR PEER REVIEW 15 of 17

Torque Output power 6000 1200

5000 1000

4000 800

m) ∙

3000 600 Torque (N Torque

2000 400 (kW) power Output

1000 200

0 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 speed (r/min)

FigureFigure A2. A2.TorqueTorque-speed-speed and and output output power power-speed-speed characteristicscharacteristics to to inverter inverter induction induction motor . drive.

TableTable A1. A1. MainMain construction construction data ofof the the induction induction motor. motor.

WeightWeight 14001400 kg kg Stator outer diameter 676 mm StatorStator innerouter diameter diameter 400676 mm mm StatorRotor innerinner diameter diameter 388400 mm mm RotorArmature inner length diameter 300388 mm mm Stator slot section 563 mm2 ArmatureRotor slot section length 168300 mm mm2 NumberStator ofslot stator section slots 563 60 mm2 NumberRotor sl ofot rotor section slots 168 72 mm2 Airflow forced air-cooling 1 m3/s Number of stator slots 60 Number of rotor slots 72 References Airflow forced air-cooling 1 m3/s 1. Steimel, A. Electric Traction-Motive Power and Energy Supply; Oldenbourg Industrieverlag GmbH: Munich, ReferencesGermany, 2008. 2. Koseki, T. Technical Trends of Railway Traction in the World. In Proceedings of the Power Electronics 1. Steimel,Conference A. Electric (IPEC Traction 2010), Sapporo,-Motive Power Japan, and 21–24 Energy June 2010;Supply pp.; Oldenbourg 2836–2841. Industrieverlag GmbH: Munich, 3.Germany,Bolvashenkov, 2008. I.; Kammermann, J.; Herzog, H. Methodology for Selecting Electric Traction Motors and 2. Koseki,its ApplicationT. Technical to VehicleTrends Propulsionof Railway Systems. Traction In Proceedingsin the World. of theIn Proceedings International Symposiumof the Power on PowerElectronics ConferenceElectronics, (IPEC Electrical 2010), Drives,Sapporo, Automation Japan, 21 and–24 MotionJune 2010 (SPEEDAM; pp. 2836 2016),–2841. Anacapri, Italy, 22–24 June 2016; 3. Bolvashenkov,pp. 1214–1219. I.; Kammermann, J.; Herzog, H. Methodology for Selecting Electric Traction Motors and 4. Le Moal, E.; Chamaret, A.; Mannevy, P.; Bouger, O. The Permanent Magnet Synchronous Motor from a its Application to Vehicle Propulsion Systems. In Proceedings of the International Symposium on Power Customer Point of View: REGIO 2N vs. REGIOLIS. In Proceedings of the International Conference on Electronics, Electrical Drives, Automation and Motion (SPEEDAM 2016), Anacapri, Italy, 22–24 June 2016; Electrical Systems for Aircraft, Railway, Ship Propulsion and Road Vehicles & International Transportation pp. 1214–1219. Electrification Conference (ESARS-ITEC 2016), Railway, Toulouse, France, 2–4 November 2016; pp. 1–4. 4. 5.Le Moal,Ronanki, E.; Chamaret, D.; Singh, A.; S.A.; Mannevy, Williamson, P.; Bouger, S.S. Comprehensive O. The Permanent Topological Magnet Overview Synchronous of Rolling Motor Stock from a CustomerArchitectures Point of and View: Recent REGIO Trends 2N in Electric vs. REGIOLI RailwayS. Traction In Proceedings Systems. IEEE of the Trans. International Transp. Electr. Conference2017, 3, on Electrical724–738. Systems [CrossRef for] Aircraft, Railway, Ship Propulsion and Road Vehicles & International 6.TransportaRind, S.J.;tion Ren, Electrification Y.; Hu, Y.; Wang, Conference J.; Jiang, (ESARS L. Configurations-ITEC 2016 and), Toulouse, Control ofFrance, traction 2– Motors4 November for Electric 2016; pp. 1–4. Vehicles: A Review. Chin. J. Electr. Eng. 2017, 3, 1–17. 5. Ronanki, D.; Singh, S.A.; Williamson, S.S. Comprehensive Topological Overview of Rolling Stock Architectures and Recent Trends in Electric Railway Traction Systems. IEEE Trans. Transp. Electr. 2017, 3, 724–738. 6. Rind, S.J.; Ren, Y.; Hu, Y.; Wang, J.; Jiang, L. Configurations and Control of traction Motors for Electric Vehicles: A Review. Chin. J. Electr. Eng. 2017, 3, 1–17. 7. Gong, T.; Ma, G.; Qian, H.; Liu, Ku.; Liu, Ka.; Wang, C.; Zhao, Z.; Zhang, W. Electromagnetic Investigation of a High-Temperature Superconducting Linear Synchronous Motor for High-Speed Railway. IEEE Trans. Appl. Superconduct. 2018, 28, doi:10.1109/TASC.2018.2790940.

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