EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL EE A Course Material on EE – 6361 ELECTRICAL DRIVES & CONTROL By Mr. S.SATHYAMOORTHI /R.RAJAGOPAL ASSISTANT PROFESSOR DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING SASURIE COLLEGE OF ENGINEERING VIJAYAMANGALAM – 638 056 1 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL QUALITY CERTIFICATE This is to certify that the e-course material Subject Code : EE- 6361 Subject : Electrical Drives & Control Class : II Year MECH Being prepared by me and it meets the knowledge requirement of the university curriculum. Signature of the Author Name: R.RAJAGOPAL,S.SATHYAMOORTHI Designation: AP/EEE This is to certify that the course material being prepared by Mr.S.Sathyamoorthi / R.Rajagopal is of adequate quality. He has referred more than five books among them minimum one is from aboard author. Signature of HD Name: Mr. E.R.Sivakumar SEAL 2 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL EE6361 ELECTRICAL DRIVES AND CONTROL Unit-I Introduction Basic elements-types of electric drives-factors influencing electric drives-heating and cooling curves- loading conditions and classes of duty-Selection of power rating for drive motors with regard to thermal overloading and load variation factors Unit-II Drive motor characteristics Mechanical characteristics- speed- torque characteristics of various types of load and drive motors - braking of electrical motors-dc motors: shunt, series, compound motors-single phase and three phase induction motors Unit-III Starting methods Types of d.c motor starters-typical control circuits for shunt and series motors-three phase squirrel and slip ring induction motors Unit-IV Conventional and solid state speed control of D.C Drives Speed control of DC series and shunt motors-Armature and field control, ward-leonard control system- using controlled rectifiers and DC choppers –applications Unit-V Conventional and solid state speed control of AC drives Speed control of three phase induction motor-Voltage control, voltage/frequency control, slip power recovery scheme-using inverters and AC voltage regulators-applications TEXT BOOKS 1. VEDAM SUBRAMANIAM “Electric drives (concepts and applications)”, Tata McGraw-Hill.2001 2. NAGARATH.I.J & KOTHARI .D.P,”Electrical machines”, Tata McGraw-Hill.1998 REFERENCES 1. PILLAI.S.K “A first course on Electric drives”, Wiley Eastern Limited, 1998 2. M.D. SINGH, K.B.KHANCHANDANI,”Power electronics,” Tata McGraw-Hill.1998 3. H.Partab,”Art and science and utilization of electrical energy,”Dhanpat Rai and sons, 1994 3 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL PAGE CHAPTER CONTENT NO 1 INTRODUCTION TO ELECTRICAL DRIVES INTRODUCTION 7 1.1 BLOCK DIAGRAM OF AN ELECTRICAL DRIVES 7 1.1.1 BASIC COMPONENT (or) ELEMENTS OF ELETCRIC DRIVES 8 1.2 FACTORS INFLUENCING THE CHOICE OF ELECTRICAL DRIVES 9 1.3 CLASSIFICATION OF ELECTRIC DRIVES WITH FACTOR 10 1.3.1 Group drive 10 1.3.2 Individual drive 10 1.3.3 Multimotor drive 11 1.4 LOAD CONDITIONS IN MOTOR 11 1.4.1 Classification of loads 11 1.4.2 Different type of industrial loads 11 1.5 HEATING AND COOLING CURVES 12 1.6 CLASSES OF MOTOR DUTY 15 1.7 SELECTION OF POWER RATING OF MOTORS 18 1.7.1 Continuous duty and constant load 18 1.7.2 Continuous duty and variable load 18 1.7.3 Short time rating of motor 22 2 DRIVE MOTOR CHARACTERISTICS 2.1 TYPES OF ELECTRICAL MACHINES 25 2.1.1 Applications of Dc Motor 25 2.1.2 Characteristics of Dc Motors 25 2.1.3 Types of Electric Braking 26 2.2 DC SHUNT MOTORS 26 2.2.1 Characteristics of Dc Shunt Motor 26 2.2.2 Electric Braking in Dc Shunt Motor 28 2.3 DC SERIES MOTOR 31 2.3.1 Characteristics of Dc Series Motor 31 2.3.2 Electric Braking in Dc Series Motor 33 2.4 COMPOUND DC MOTOR 34 2.4.1 Characteristics of DC Compound Motor 34 2.4.2 Electric Braking in DC Compound Motor 35 2.5 APPLICATIONS OF DC MOTORS 36 2.6 SINGLE PHASE INDUCTION MOTORS 36 2.6.1 CONSTRUCTION AND WORKING PRINCIPLE 36 2.6.2 TORQUE-SLIP CURVE FOR INDUCTION MOTOR 38 2.6.3 ELECTRIC BRAKING IN AC INDUCTION MOTOR 38 2.7 THREE PHASE INDUCTION MOTOR 41 2.7.1 CONSTRUCTIONAL DETAILS 42 4 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL 2.7.2 WORKING PRINCIPLE OF THREE PHASE INDUCTION MOTOR 45 3 STARTING METHODS 47 3.1 INTRODUCTION 47 3.1.1 Prime Purpose (or) Necessity of a Starter For Motors 47 3.1.2 Protective Devices in a DC/AC Motor Starter 47 3.1.3 Starters for DC Motor 47 3.2 THREE POINT STARTER 48 3.3 FOUR POINT STARTER 49 3.4 TWO POINT STARTER 50 3.5 STARTERS FOR AC STARTERS 52 3.5.1 Necessity for Starter 52 3.5.2 Prime Purpose of a Starter For Motors 53 3.5.3 Need For Starter in an Induction Motor 53 3.6 D.O.L STARTER 53 3.7 STATOR RESISTANCE (OR) PRIMARY RESISTANCE STARTER 54 3.8 PRIMARY REACTANCE STARTER (or) AUTO TRANSFORMER STARTERS 55 3.9 STAR –DELTA STARTER 58 3.10 ROTOR RESISTANCE STARTERS 59 3.11 COMPARE THE INDUCTION MOTOR STARTERS 60 4 CONVENTIONAL & SOLID STATE SPEED CONTROL OF D.C DRIVES 4.1 INTRODUCTION 62 4.2 EXPRESSION FOR SPEED FOR A DC MOTOR 62 4.3 Applications of DC Drives 62 4.4 Advantages of DC Drives 62 4.5 Conventional Methods of Speed Control 63 4.5.1 Speed control of DC Shunt Motors 63 4.5.2 Speed control of DC Series Motors 64 4.5.3 Ward Leonard Control System 65 4.6 Solid state Speed Control of DC Motor 66 4.6.1 Single phase Controlled rectifier fed DC drives 67 5 CONVENTIONAL & SOLID STATE SPEED CONTROL AC DRIVES 5.1 INTRODUCTION 72 5.2 SPEED CONTROL OF DRIVES 72 5.3 Advantages of Induction motor 72 5.4 Applications of Induction motors 72 5.5 Speed control of three phase induction motor 73 5.6 Slip Power Recovery Scheme 75 5 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL UNIT-I INTRODUCTION Basic elements Types of electric drives Factors influencing electric drives Heating and cooling curves Loading conditions and classes of duty Selection of power rating for drive motors with regard to thermal overloading and load variation factors 6 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL INTRODUCTION UNIT 1 1. INTRODUCTION Drive: A combination of prime mover, transmission equipment and mechanical Working load is called a drive Electric drive: An Electric Drive can be defined as an electromechanical device for converting electrical energy to mechanical energy to impart motion to different machines and mechanisms for various kinds of process control. 1.1 BLOCK DIAGRAM OF AN ELECTRICAL DRIVES The basic block diagram for electrical drives used for the motion control is shown in the following figure1.1 SOURCE POWER MOTOR LOAD AC (or) DC MODULATOR INPUT CONTROL SENSING UNIT UNIT Fig 1.1 Block Diagram for Electrical Drives The aggregate of the electric motor, the energy transmitting shaft and the control equipment by which the motor characteristics are adjusted and their operating conditions with respect to mechanical load varied to suit practical requirements is called as electric drive. Drive system=Drive + load 7 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL 1.1.1 BASIC COMPONENT (or) ELEMENTS OF ELETCRIC DRIVES Block diagram of electric drive: 1. Load: usually a machinery to accomplish a given task. Eg-fans, pumps, washing machine etc. 2. Power modulator: modulators (adjust or converter) power flow from the source to the motion 3. Motor: actual energy converting machine (electrical to mechanical) 4. Source: energy requirement for the operation the system. 5. Control: adjust motor and load characteristics for the optimal mode. Power modulators: Power modulators regulate the power flow from source to the motor to enable the motor to develop the torque speed characteristics required by the load. The common function of the power modulator is, They contain and control the source and motor currents with in permissible limits during the transient operations such as starting, braking, speed reversal etc. They converts the input electrical energy into the form as required by the motors. Adjusts the mode of operation of the motor that is motoring, braking are regenerative. Power modulators may be classified as, Converters uses power devices to convert uncontrolled valued to controllable output. Switching circuits switch mode of operation Variable impedance Converters They provide adjustable voltage/current/frequency to control speed, torque output power of the motor. The various type of converters are, AC to DC rectifiers DC to DC choppers AC to AC choppers AC to AC –AC voltage controllers (voltage level is controlled) Cyclo converter (Frequency is controlled) DC to AC inverters Switching circuits Switching circuits are needed to achieve any one of the following. Changing motor connection to change its quadrant of operation. Changing motor circuits parameters in discrete steps for automatic starting and braking control. For operating motors and drives according to a predetermine sequence To provide inter locking their by preventing maloperation 8 R.RAJAGOPAL, S.SATHYAMOORTHI,AP/EEE 2015-16 EE 6361- ELECTRICAL DRIVES & CONTROL II/III MECHANICAL Disconnect under up normal condition Eg: electromagnetic contacters, PLC in sequencing and inter locking operation, solid state relays etc.