control of AC machines

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control of AC machines

  1. 1. Control of AC Machines Pekik Argo Dahono
  2. 2. AC Machines1. Synchronous machines• Wound field• Permanent magnet• Reluctance2. Induction machines• Squirrel-cage rotor• Wound rotor
  3. 3. Equivalent Circuit of Induction Machines is Rs Lls Llr is Rs Lls Llr ir irvs Rc Lm Rr vs Lm Rr s s is Rs Ll is Rs Ll iR iRvs Ls RR vs LM RR s s
  4. 4. Analysis of Induction Machines Torque :Rotor current : 3P E 2 RR Te  Pg /  m    EIr  2 s RR / s 2  Ll 2 RR / s 2  Ll 2 3P E 2 RR s Te   Airgap power : 2  RR  sLl 2 2 3E 2 R RPg  3I r2 RR / s   s RR / s 2  Ll 2  Maximum Torque : 2 3P  E  1Rotor losses : Tem    4    LlPr  3I r2 RR RROutput Mechanic : at s m   Ll 1 sPm  3I r2 RR s Normal operating conditions RR  sLl 2 2Airgap power : Rotor losses : Output  1 : s :1 - s 3P E 2 s Te  2 R R
  5. 5. Torque and Current Characteristics of Induction MachinesTorque Current Slip 1 0 1 I FL Slip 1 0
  6. 6. Pole Changing of Induction Machines• Discrete and limited speed control. Low speed Torque• Suitable for some applications. High speed• Can be designed with Load constant torque, constant HP, and variable torque.• Available up to Speed medium HP motors.
  7. 7. Voltage Control of Induction Motors• Percent losses is increased when the speed is decreased. AC source IM• Suitable for soft-start control.• Why-delta, autotransformer, part-winding, primary resistor starters are commonly used to limit the starting current.• Suitable for speed control of V1  V2  V3 small HP motors. Torque V3• Voltage control can be done by using TRIAC or antiparallel thyristors. Load• Wide speed control range is V2 achievable by using high slip V1 motors. Speed
  8. 8. Variable-Voltage Variable-FrequencyTorque : E6 E5 E4 E3 E2 E1 RR sl 2 3P  E  f 6 f 5 f 4 f3 f 2 f1Te    Torque   2    RR   sl Ll 2 2 Load 3P  E   sl 2Te    2    RR SpeedMaximum Torque : 2 3P  E  1Tem    4    Ll
  9. 9. Variable-Voltage Variable-Frequency Te V sl Vboost 0 
  10. 10. Scheme of VVVF System Smoothing inductor AC Motor AC source 3 Smoothing capacitor vout Controlled Square - wave rectifier inverter VVI System AC Motor AC source 3 Smoothing capacitor vout Uncontrolled PWM inverter rectifier PWM System
  11. 11. Simulated Results : VVVF System
  12. 12. Simulated Results : VVVF
  13. 13. Slip-Controlled Induction Motor Drives V va va  V sin Te* sl  *     vb  V sin   23 vb GT vc  V sin  23     vc  r 3P  E   sl 2 Te    2    Rr
  14. 14. Vector Control Pg  3EI r E  Lm I m Pg 3P Te   Lm I m I r Im iR m 2 RR ImIs LM E Is  2 Im  I r2  tan 1 s Ir Rr Lm I m  I r s R I s   sl  r r Lm I m
  15. 15. Vector Control * Is * ia  2 I s sin  ia * Ir I s  I m  I r2  Te* 2 2 *   2 I s sin   23 * : Im s   ib ib 3P  s  tan 1 Ir ic  * 2 I s sin  23   * *Im  ic Lm g  sl   Rr :  r
  16. 16. Vector Control Ed Three - Phase VSI Inverter IM Current Controller ia , ib , ic * * * ia , ib , ic I R2 *  I m2 * Signal Generator *Im   I*   tan 1 m   I*   et *  Rr * Speed Controller IR  * RR I R  sl e r * LM I m
  17. 17. Wound-Rotor Induction Motor Drives AC source R1  Rr  Rr  Rr r 2 3 4 Torque 4 3 2 Rr Rr Rr R1 r Load Speed
  18. 18. Slip-Power Recovery Drives Wound rotor Induction motorAC Source
  19. 19. Variable-Speed Power Generation Wound rotor Induction motor Ps , s Psl , sl AC Source cycloconverter Pm , m s  m  sl Ps : Psl : Pm  1 : s : 1  s
  20. 20. Synchronous Motor Drives Synchronous MachineAC source PG Triger Triger circuit circuit Id *  Current  controller
  21. 21. Self-Controlled Principle N P  EI s1 cos T he phase angle of E is detected by using S a position sensor. T he emf is E  K m I f If the field current is constant hen the t magnitude of emf E is also constant. T orque isI s1 E0 Te  P / m  KI f I s1 cos
  22. 22. Synchronous Motor Drives Synchronous Machine PG Gate driver Current Controller ia  I s sin  *  ib  I s sin  23   * Is *   ic  I s sin  23  *     

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