DESIGN OF CONTROLLERS QUESTION BANK

1.     Discuss  the current controller design  using i) P controller ii) PI controller  for a separately excited  dc motor drive system.                                                            

2.     Derive the closed loop transfer function  of converter fed separately excited dc motor

3.   A 50KW, 240 V, 1700 rpm separately excited dc motor is controlled by converter. The field current is maintained at field current 1.4 A and the machine back emf constant Kv=0.91V/A/rad/s. The armature resistance is Rm =0.1 Ω and the viscous friction constant is B= 0.3 NM/rad/sec. The amplification of speed sensor is K1 = 95mV/rad/s and the gain of power controller is K2 = 100. i) Determine the reference voltage Vr to drive the motor at the rated speed. ii) If the reference voltage is kept unchanged, determine the speed at which the motor torque develops rated torque.                16

4. From basic principles derive the transfer function for separately excited DC motor load system.                                                                                                                     

5.     Explain the step by step procedure  for the design of  current controller                        

6.   Explain the closed loop speed control   for armature  voltage control  and field weakening mode for a dc drive                                                                                      

7. Explain the factors involved in converter selection and equations involved in controller characteristics.                                                                                                            

The following basic features govern the design of speed control of an electric motor.

i) Range of speed control

ii) Smoothness of speed control

iii) Economic justifiability

iv) Stability of operation

v) Direction of speed control

            vi) Permissible load at different speed