Advanced Electric Drives

Q.1. What do you understand by three level inverter?

Q.2. What is space vector modulation system?

Q.3. Explain the CSI based control of synchronous motor.

Q.4. What are the various methods used for speed control of DC motors?

Q.5. Briefly explain the AC dynamic braking system of Induction motor drives.

Q.6. List the starting methods of induction motors.

Q.7. How frequency can be controlled by power electronics devices? Explain briefly.

Q.8. Draw the necessary diagram for explaining the load equalization.

Q.9. Explain the dynamic braking of synchronous motor with VSI.

Q.10. Draw the speed-torque characteristics of regenerative braking for synchronous motor.

Q.1. Explain the voltage source inverter control of induction motor.

Q.2. What are the power limitations in armature voltage control in DC drives?

Q.3. A 200V, 10.5A, 2000 rpm shunt motor has the armature and field resistance of 0.5 ohm and 400 ohm respectively. It drives a load whose torque is constant at rated motor torque. Calculate motor speed if the source voltage drops to 175V.

Q.4. Explain the plugging braking for induction motor. What are the advantages and dis-advantages of electric braking?

Q.5. Explain the slip-recovery scheme with Static Kramer drive.

Q.6. Explain the stator voltage control for speed control of induction motor.

Q.7. Explain the control characteristic of an open loop v/f controlled synchronous motor.

Q.1. How do you define passive and active load torques? Explain the multi-quadrant operation of an electric motor driving a hoist load. Also discuss the different modes of operations of an electric drive.

Q.2. A 220V, 970 rpm, 100 A DC separately excited motor has an armature resistance of 0.05 ohm. It is braked by plugging from an initial speed of 1000 rpm. Calculate - (i) Resistance to be placed in armature circuit to limit braking current to twice the full load value. (ii) Braking torque and (iii) Torque when the speed has fallen to zero.

Q.3. Why the current source inverter fed induction motor drive is operated at a constant rated flux? Also explain the static Scherbius drive of induction motor drives.

Q.4. A 2200 V, 2600 kW, 735 rpm, 50 Hz and 8-pole 3-phase squirrel cage induction motor has the following parameters referred to the stator: Rs=0.075 ohm, Rr'=0.1 ohm, Xs=0.45 ohm, Xr'=0.55 ohm. Stator winding is delta connected and consists of two sections connected in parallel. (i) Calculate starting torque and maximum torque as a ratio of rated torque if the motor is started by star-delta switching. (ii) What will be the value of maximum line current and torque during starting if the part winding method of starting is employed?

Q.5. Write a short note on - (Any two) (a) Closed loop speed and torque control of SRM. (b) Implementation of DSP based motion control. (c) Speed and torque control in PMSM. (d) Various topologies for SRM drives.