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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
400 V
800 V
200 V
2002 V
Answer: Option
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
about 350 rpm
about 250 rpm
about 175 rpm
about 125 rpm
Answer: Option
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.
True
False
Answer: Option
Explanation:

They operate in a sequence.

34.
The terminals of a power MOSFET are called
emitter, base, collector
source, gate, drain
source, base, drain
emitter, gate, drain
Answer: Option
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.

Both A and R are correct and R is correct explanation of A
Both A and R correct but R is not correct explanation of A
A is correct but R is wrong
A is wrong but R is correct
Answer: Option
Explanation:

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

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