Electronics and Communication Engineering - Power Electronics

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

Answer: Option C

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

A. about 350 rpm
B. about 250 rpm
C. about 175 rpm
D. about 125 rpm

Answer: Option D

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

Answer: Option B

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

Answer: Option B

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

Answer: Option A

Explanation:

Since duration of surge current is small, the associated energy is small.