Exercise: Power Electronics

Questions for: Power Electronics

Assertion (A): A transistor requires a continuous base signal for conduction but a thyristor requires a gate pulse.

Reason (R): Transistor find widespread application in power electronic circuits.

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: C

Transistors are used but not very widely.

A single phase half wave controlled rectifier circuit has a free wheeling diode. The load is a combination of R and L. The firing angle is a. The period of conduction of SCR and free wheeling diode respectively are
A:
a < ωt < p and p < ωt < (2p + a)
B:
a < ωt < p and p < ωt < 2p
C:
a < ωt < (p + a) and (p + a) < ωt < 2p
D:
a < ωt < p and p < ωt < (2p - a)
Answer: A

SCR conducts from a to p and free wheeling diode from p to (2p + a).

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: A

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

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: B

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

In a multiphase chopper, all choppers operate together.
A:
True
B:
False
C:
D:
Answer: B

They operate in a sequence.

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