A 750 A circuit uses thyristor of current rating 175 A. If derating is 25%, the

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Question
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

Correct Answer

6

Explanation

A 750 A circuit uses thyristor of current rating 175 A. If derating is 25%, the number of thyristors

.

Power Electronics problems

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1. 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.

2. A 3 phase bridge inverter is fed by 400 V battery. The load is star connected and has a resistance of 10 ? per phase. The peak value of load current is
Options
A. 40 A
B. 20 A
C. 10 A
D. 5 A

3. During forward blocking state of SCR, the voltage and current respectively are
Options
A. high and high
B. low and low
C. high and low
D. low and high

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

6. 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

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

8. 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

9. 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

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