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EEEB283 Electrical Machines & Drives

EEEB283 Electrical Machines & Drives. Introduction to Electrical Drives By Dr. Ungku Anisa Ungku Amirulddin Department of Electrical Power Engineering College of Engineering. Definition of Electrical Drives. Drives – system employed for motion control

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EEEB283 Electrical Machines & Drives

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  1. EEEB283 Electrical Machines & Drives Introduction to Electrical Drives By Dr. UngkuAnisaUngkuAmirulddin Department of Electrical Power Engineering College of Engineering EEEB283 - Electrical Machines & Drives

  2. Definition of Electrical Drives • Drives – system employed for motion control • Motion control requires prime movers • Electrical Drives – Drives that employ Electric Motors as prime movers EEEB283 - Electrical Machines & Drives

  3. Conventional Electric Drives • Disadvantage : • Bulky • Expensive • Inefficient • Complex EEEB283 - Electrical Machines & Drives

  4. Modern Electric Drives • Small • Efficient • Flexible • Interdisciplinary feedback EEEB283 - Electrical Machines & Drives

  5. Electric Drives Application • Line Shaft Drives • Oldest form • Single motor, multiple loads • Common line shaft or belt • Inflexible • Ineffcient • Rarely used EEEB283 - Electrical Machines & Drives

  6. Electric Drives Application • Single-Motor, Single-Load Drives • Most common • Eg: electric saws, drills, fans, washers, blenders, disk-drives, electric cars. EEEB283 - Electrical Machines & Drives

  7. Electric Drives Application • Multimotor Drives • Several motors, single mechanical load • Complex drive functions • Eg: assembly lines, robotics, military airplane actuation. EEEB283 - Electrical Machines & Drives

  8. Basic Components of Electric Drives • Motor • Power Processing Unit (Electronic Converter) • Control Unit • Power Source • Mechanical Load feedback EEEB283 - Electrical Machines & Drives

  9. Basic Components of Electric Drives - Motor • DC motors - Permanent Magnet or wound-field (shunt, separately excited, compound, series) • AC motors – Induction, Synchronous (wound –rotor, IPMSM, SPMSM), brushless DC • Selection of machines depends on many factors, e.g.: • application • cost • efficiency • environment EEEB283 - Electrical Machines & Drives

  10. Basic Components of Electric Drives – Power Source • Regulated (e.g: utility) or Unregulated (e.g. : renewable energy) • DC source • Batteries • fuel cell • photovoltaic • AC source • Single- or three- phase utility • wind generator EEEB283 - Electrical Machines & Drives

  11. Basic Components of Electric Drives – Power Processing Unit • Provides a regulated power supply to motor • Combination of power electronic converters • Controlled rectifiers, inverters –treated as ‘black boxes’ with certain transfer function • More efficient • Flexible • Compact • AC-DC , DC-DC, DC-AC, AC-AC EEEB283 - Electrical Machines & Drives

  12. Basic Components of Electric Drives – Power Processing Unit EEEB283 - Electrical Machines & Drives

  13. Basic Components of Electric Drives – Power Processing Unit EEEB283 - Electrical Machines & Drives

  14. Basic Components of Electric Drives – Control Unit • Supervise operation • Enhance overall performance and stability • Complexity depends on performance requirement • Analog Control – noisy, inflexible, ideally infinite bandwidth • Digital Control – immune to noise, configurable, smaller bandwidth • DSP/microprocessor – flexible, lower bandwidth, real-time • DSPs perform faster operation than microprocessors (multiplication in single cycle), can perform complex estimations EEEB283 - Electrical Machines & Drives

  15. Basic Components of Electric Drives – Mechanical Load • Wide variation of Torque-speed (T-) characteristics • Load torque is function of speed • where k = integer or fraction • Mechanical power of load: • and Speed in rpm Angular speed in rad/s EEEB283 - Electrical Machines & Drives

  16. Basic Components of Electric Drives – Mechanical Load EEEB283 - Electrical Machines & Drives

  17. Basic Components of Electric Drives – Mechanical Load • Torque independent of speed , k = 0 • Hoist • Elevator • Pumping of water or gas against constant pressure EEEB283 - Electrical Machines & Drives

  18. Basic Components of Electric Drives – Mechanical Load • Torque proportional to square of speed , k = 2 • Fans • Centrifugal pumps • Propellers EEEB283 - Electrical Machines & Drives

  19. Basic Components of Electric Drives – Mechanical Load • Torque inversely proportional to speed , k = -1 • Milling machines • Electric drill • Electric saw EEEB283 - Electrical Machines & Drives

  20. TL Te , m With constant J, • First order differential equation for angular frequency (or velocity) • Second order differential equation for angle (or position) Torque Equation for Rotating Systems J EEEB283 - Electrical Machines & Drives

  21. m1 m N1 Motor Te Load 1, TL1 J2 m2 N2 Load 2, TL2 J1 Torque Equation for Rotating Systems with Gears • Low speed applications use gears to utilize high speed motors EEEB283 - Electrical Machines & Drives

  22. m1 m N1 Motor Te Load 1, TL1 J2 m N2 Load 2, TL2 Motor Te Equivalent Load , TLequ J1 Jequ Torque Equation for Rotating Systems with Gears TLequ = TL1 + a2TL2 a2 = N1 / N2 EEEB283 - Electrical Machines & Drives

  23. SPEED Synchronous motor Induction motor Separately excited / shunt DC motor Series DC motor TORQUE Steady State Motor T- Characteristic By using power electronic converters, the motor characteristic can be varied EEEB283 - Electrical Machines & Drives

  24. Te TL Steady state Speed, r r1 r2 r3 Steady State Motor and LoadT- Characteristic Torque • At constant speed, Te= TL • Steady state speed is at point of intersection between Te and TLof the steady state torque characteristics Speed EEEB283 - Electrical Machines & Drives

  25. Te m m Te  Te T Te m m Torque-Speed Quadrant of Operation • Direction of positive (forward) speed is arbitrary chosen • Direction of positive torque will produce positive (forward) speed Quadrant 1 Forward motoring Quadrant 2 Forward braking Quadrant 3 Reverse motoring Quadrant 4 Reverse braking EEEB283 - Electrical Machines & Drives

  26. References • El-Sharkawi, M. A., Fundamentals of Electric Drives, Brooks/Cole Publishing Company, California, 2000. • Krishnan, R., Electric Motor Drives: Modelling, Analysis and Control, Prentice-Hall, New Jersey, 2001. • Nik Idris, N. R., Short Course Notes on Electrical Drives, UNITEN/UTM, 2008. • Ahmad Azli, N., Short Course Notes on Electrical Drives, UNITEN/UTM, 2008. EEEB283 - Electrical Machines & Drives

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