In a single phase full wave ac regulator the rms value of load current is 20 A l

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Question
In a single phase full wave ac regulator the rms value of load current is 20 A load is purely resistive. Then
Options
A. average thyristor current will be less than 20 A but rms thyristor current will be more than 20 A
B. both the average and rms thyristor currents will be less than 20 A
C. both the average and rms thyristor currents will be more than 20 A
D. rms thyristor current will be 20 A and average thyristor current will be 10 A

Correct Answer

both the average and rms thyristor currents will be less than 20 A

Explanation

Each thyristor conducts for 50% of time.

Power Electronics problems

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1. An RC snubber circuit is used to protect a thyristor against :
Options
A. false triggering
B. failure to turn on
C. switching transients
D. failure to commutate

2. In a series inverter supplying a load resistance R, the commutating elements L and C should be such that
Options
A.
B.
C.
D.

3. Which of these triggering methods for series connected SCRs use LASCR in the gate circuit?
Options
A. Resistance triggering
B. Simultaneous triggering
C. Sequential triggering
D. Optical triggering

4. A 750 A circuit uses thyristor of current rating 175 A. If derating is 25%, the number of thyristors in parallel is
Options
A. 3
B. 4
C. 6
D. 10

5. A single phase half wave controlled rectifier circuit is feeding on RL load. The circuit has a freewheeling diode. The input voltage is v = V_m sin ?t. If I₀ is the load current during the conduction of freewheeling diode, the KVL equation during the conduction of free wheeling diode is
Options
A.
B.
C.
D.

7. HVDC transmission systems generally use
Options
A. 12 pulse converters
B. 6 pulse converters
C. 3 pulse converters
D. either 12 or 6 pulse converters

8. A dc separately excited motor has a constant field current. The armature is fed from a single phase supply through a semi-converter. When a = 0, speed is 600 rpm. If a = 90�, the speed is likely to be
Options
A. about 300 rpm
B. about 150 rpm
C. about 75 rpm
D. about zero

9. Assertion (A): An inverter does not require forced commutation
Reason (R): A series inverter is a forced commutation inverter.
Options
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

10. A single phase series converter is used for
Options
A. high voltage output
B. high current output
C. high voltage and high current output
D. improving the circuit efficiency

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