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Class 1

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Introduction

Introduction

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  • 1. EPE10 104ELECTRIC DRIVESDr. Sasidharan Sreedharanwww.sasidharan.webs.com
  • 2. OBJECTIVETo provide a strong background onvarious methods of speed control ofdifferent electrical machines.
  • 3. MODULE 1Components of electrical Drives – electric machines,power converter, controllers - dynamics of electric drive -torque equation - equivalent values of drive parameters-components of load torques types of load - fourquadrant operation of a motor –– steady state stability -load equalization – classes of motor duty- determinationof motor rating
  • 4. MODULE 2DC motor drives – dc motors & their performance (shunt,series, compound, permanent magnet motor, universalmotor, dc servomotor) – braking – regenerative, dynamicbraking, plugging – Transient analysis of separately excitedmotor – converter control of dc motors – analysis ofseparately excited & series motor with 1-phase and 3-phaseconverters – dual converter – analysis of chopper controlleddc drives – converter ratings and closed loop control -transfer function of self, separately excited DC motors –linear transfer function model of power converters – sensingand feeds back elements – current and speed loops, P, PI andPID controllers – response comparison – simulation ofconverter and chopper fed DC drive.
  • 5. MODULE 3Induction motor drives – stator voltage control ofinduction motor – torque-slip characteristics – operationwith different types of loads – operation withunbalanced source voltages and single phasing – analysisof induction motor fed from non-sinusoidal voltagesupply – stator frequency control – variable frequencyoperation – V/F control, controlled current andcontrolled slip operation – effect of harmonics andcontrol of harmonics – PWM inverter drives – multi-quadrant drives – rotor resistance control – slip torquecharacteristic – torque equations, constant torqueoperation – slip power recovery scheme – torqueequation – torque slip characteristics – power factor –methods of improving .
  • 6. MODULE 4Synchronous motor drives – speed control ofsynchronous motors – adjustable frequency operation ofsynchronous motors – principles of synchronous motorcontrol – voltage source inverter drive with open loopcontrol – self controlled synchronous motor withelectronic commutation – self controlled synchronousmotor drive using load commutated thyristor inverter.
  • 7. REFERENCES1. R. Krishnan, Electical Motor Drives, PHI2 GK Dubey, Fundamentals of Electrical Drives,Narosa3. GK Dubey, Power Semi-conductor ControlledDrives, Prentice Hall4. Bimal K Bose, Modern Power Electronics & ACDrives, PHI5. S A Nasar, Boldea, Electrical Drives, CRC press6. M A Elsharkawi, Fundamentals of Electrical Drives,Thomson Learning7. W Leohnard, Control of Electric Drives, Springer8. Murphy and Turnbill, Power Electronic Control ofAC motors, Pergamon Press9. Vedam Subarhmanian, Electric Drives, TMH
  • 8. Examination Internal continuous assessment: 100 marksInternal continuous assessment is in the form ofperiodical tests, assignments, seminars or a combinationof all whichever suits best. There will be a minimum oftwo tests per subject. The assessment details are to beannounced to students’ right at the beginning of thesemester by the teacher. End semester Examination: 100 marks
  • 9. Modern Variable Speed System A modern variable speed system has four components: 1. Electric Motor 2. Power Converter - Rectifiers - Choppers - Inverters3. Controllers – matching the motor and power converter to meet the load requirements 4. Load
  • 10. Electric MotorsTypes of electric motors presently used forspeed control applications are: 1. DC motors AC motors Shunt Induction Series Wound rotor Compound synchronous Separately excited Permanent magnet Switched synchronous reluctance motors Reluctance motors
  • 11. Motor Selection1. Cost2. Thermal capacity3. Efficiency4. Torque-speed profile5. Acceleration6. Power density, volume of the motor7. Ripple, cogging torque8. Peak torque capability9. Suitability for hazardous environment10. Availability of spare parts
  • 12. Electric Motors (contd’)For position servo applications: The peak torque and thermal capabilities together with ripple and cogging torques are important characteristics for servo application Higher peak torques decrease the acceleration/deceleration times Minimum cogging and ripple torques help to attain higher positioning repeatability and higher thermal capability leading to a longer motor life and a higher amount of loading
  • 13. Power ConvertersThe power converters driving the motors are: 1. Controlled Rectifiers Controlled rectifiers are fed from single and three-phase AC main supply.Vc: Voltage controlledKr: Gain (proportionality constant)
  • 14. Power Converters (contd’)2. Inverters – Voltage and current source converters are fed from a DC link. The DC link is generated with either a controlled or uncontrolled rectifier.Vc: controlled magnitude commandfc: frequency command
  • 15. Power Converters (contd’)3. Cycloconverter
  • 16. ControllersThe controllers implement the control strategygoverning the load and motor characteristicsTo match the load and motor, the input to thepower converter is controlled (manipulated) bythe controller
  • 17. Motor Drive Schematic
  • 18. Typical Controller Block
  • 19. Controllers (contd’)The inputs to the controller consists of: 1. Torque, flux, speed, and/or position commands 2. Their rate of variations to facilitate soft start, to preserve the mechanical integrity of the load 3. The actual values of torque, flux, speed, and/or position for feedback control. 4. Limiting values of currents, torque, acceleration, etc. 5. Temperature feedback, instantaneous currents and/or voltages in the motor and/or converter.
  • 20. POWER ELECTRONICS AND DRIVES What is Power Electronics ? A field of Electrical Engineering that deals with the application of power semiconductor devices for the control and conversion of electric power sensorsInputSource Power Electronics Load- AC Converters- DC Output- unregulated - AC - DC POWER ELECTRONIC CONVERTERS – the heart of power a power Reference Controller electronics system
  • 21. Modern Electrical Drive Systems Typical Modern Electric Drive Systems Power Electronic Converters Electric Motor Electric Energy Electric Energy Electric Mechanical - Unregulated - - Regulated - Energy EnergyPOWER IN Power Moto Load Electronic r Converters feedback Reference Controller
  • 22. Modern Electrical Drive SystemsOverview of AC and DC drives DC drives: Electrical drives that use DC motors as the prime mover Regular maintenance, heavy, expensive, speed limit Easy control, decouple control of torque and flux AC drives: Electrical drives that use AC motors as the prime mover Less maintenance, light, less expensive, high speed Coupling between torque and flux – variable spatial angle between rotor and stator flux
  • 23. Modern Electrical Drive SystemsOverview of AC and DC drives Before semiconductor devices were introduced (<1950) • AC motors for fixed speed applications • DC motors for variable speed applications After semiconductor devices were introduced (1960s) • Variable frequency sources available – AC motors in variable speed applications • Coupling between flux and torque control • Application limited to medium performance applications – fans, blowers, compressors – scalar control • High performance applications dominated by DC motors – tractions, elevators, servos, etc
  • 24. Modern Electrical Drive SystemsOverview of AC and DC drives After vector control drives were introduced (1980s) • AC motors used in high performance applications – elevators, tractions, servos • AC motors favorable than DC motors – however control is complex hence expensive • Cost of microprocessor/semiconductors decreasing –predicted 30 years ago AC motors would take over DC motors
  • 25. Modern Electrical Drive SystemsOverview of AC and DC drives Extracted from Boldea & Nasar
  • 26. Power Electronic Converters in ED Systems Converters for Motor Drives (some possible configurations) DC Drives AC Drives AC Source DC Source AC Source DC Source DC-AC-DC DC-DCAC-DC AC-DC-DC AC-DC-AC AC-AC DC-AC DC-DC-AC Const. Variable NCC FCC DC DC
  • 27. ConclusionAll Resource Materials(Class power points, notes, assignments etc )will be regularly posted in the website.Please visit regularly for updated information www.sasisreedhar.webs.comSent mail in case of any clarification/doubts/suggestions sasisreedhar@vidyaacademy.ac.in

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