# Electronics and Communication Engineering - Power Electronics

### Exercise :: Power Electronics - Section 1

31.

In a circuit using a full wave converter (M - 2 connection) the PIV of each thyristor is 400 V. For the same output voltage and fully controlled bridge converter, PIV will be

 A. 400 V B. 800 V C. 200 V D. 2002 V

Explanation:

In bridge connection PIV is half of that in M-2 connection.

32.

A dc separately excited motor has constant field current. The armature is fed from a single phase supply through a full converter. When a = 0, speed is 500 rpm. If a = 45°, the speed is likely to be

Explanation:

Average output voltage ∝ cos a and therefore reduced to 0.707 of the value for a = 0. Speed is nearly proportional to voltage.

33.

In a multiphase chopper, all choppers operate together.

 A. True B. False

Explanation:

They operate in a sequence.

34.

The terminals of a power MOSFET are called

 A. emitter, base, collector B. source, gate, drain C. source, base, drain D. emitter, gate, drain

Explanation:

In a MOSFET terminals are source, gate, drain irrespective of rating.

35.

Assertion (A): The surge current which an SCR can withstand is much higher than rms on state current.

Reason (R): The duration of surge current is very small.

 A. Both A and R are correct and R is correct explanation of A B. Both A and R correct but R is not correct explanation of A C. A is correct but R is wrong D. A is wrong but R is correct