1. CLOSED LOOP CONTROL OF DC DRIVES

3. Controller Requirements  Fast tracking capability  Less steady state error  Robust to load disturbance during steady state and transient conditions.

4. Methods of speed control in DC drives

5. DC Motor Speed Control Torque Speed Maximum Torque By Changing Ra Ra increasing Power loss in Ra Does not maintain maximum torque capability Poor speed regulation

6. DC Motor Speed Control Torque Speed Maximum Torque Flux Decreasing T rated Slow transient response Does not maintain maximum torque capability By Decreasing Flux

7. DC Motor Speed Control Torque Speed Maximum Torque By Changing Armature voltage T rated Va increasing good speed regulation maintain maximum torque capability

8. Speed control of DC Motors Below base speed: Armature voltage control (retain maximum torque capability) Above base speed: Field weakening (i.e. flux reduced) (Trading-off torque capability for speed) Torque speed Line of Maximum Torque Limitation Armature voltage control Field flux control  base

9. Armature and field control

10. In practice, for speeds less than the base speed (rated), the armature current and field currents are maintained at fixed values (hence constant torque operation), and the armature voltage controls the speed. For speeds higher than the base speed, the armature voltage is maintained at rated value, and the field current is varied to control the speed. However, this way the power developed Pd is maintained constant. This mode is referred to as “field weakening” operation.

17. Block diagram of closed loop control

18. Controller Design Procedure

19. Controller Design Procedure- Contd.

21. Transfer Function of Motor

23. Transfer Function of Converters

24. CURRENT CONTROL FOR DC DRIVES To derive transfer function of converter, control techniques should be explained

25. Current Control for Chopper

28. PWM Controller

29. Hysteresis Controller

31. Comparison

32. Transfer function of chopper drive

37. Three-phase Fully controlled Rectifier- transfer function

39. Introduction to PID Controllers for deriving the transfer function of current& speed controllers

45. About Kp value

46. About Ki value

47. About Kd value

48. Overall block diagram

62. Simulation