Electronics and Communication Engineering - Power Electronics

1. 

A dc circuit breaker must use

A. natural commutation
B. forced commutation
C. both natural and forced commutation
D. either natural or forced commutation

Answer: Option B

Explanation:

Natural commutation is possible only in ac circuits.


2. 

In a single phase full wave regulator feeding R-L load, the minimum firing angle can be zero.

A. True
B. False

Answer: Option A

Explanation:

Range of control of a is 0 ≤ ap.


3. 

An RC snubber circuit is used to protect a thyristor against :

A. false triggering
B. failure to turn on
C. switching transients
D. failure to commutate

Answer: Option C

Explanation:

Especially high during switching.


4. 

A DIAC has two terminals, anode and cathode.

A. True
B. False

Answer: Option B

Explanation:

They are designated as T1 and T2 because diac can conduct in both directions.


5. 

A single phase semiconverter has a freewheeling diode. If the firing angle is a and the load is purely resistive, the periods of conduction and freewheeling respectively are

A. p - a and 0
B. p - a and a
C. p + a and 0
D. p + a and a

Answer: Option A

Explanation:

Freewheeling diode conducts only when load is inductive. If load is purely resistive free wheeling diode does not come into operation.


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