OBJECTIVETo provide a strong background onvarious methods of speed control ofdifferent electrical machines.
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
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.
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 .
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.
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
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
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
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
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
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
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)
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
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
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.
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
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
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
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
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
Modern Electrical Drive SystemsOverview of AC and DC drives Extracted from Boldea & Nasar
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
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