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Multiple Choice Questions on SCR (Silicon controlled rectifier) part 1

Hello Engineers.

Q.1 If the current of an SCR increases, the forward breakdown voltage will

A. Decrease
B. Not be effected
C. Increase
D. Become zero

Ans: A

Q.2 If the gate current of an scr is increased, the forward breakdown voltage will

A. Increase
B. Decrease
C. Not be affected
D. Become infinite

Ans: C


Q.3 After firing an scr, the gate pulse is remove. The current in the scr will

A. Remain the same
B. Immediately fall to zero
C. Rise up
D. Rise a little and then fall to zero

Ans: A

Q.4 An scr conducts an appreciable current when the gate is negative and the a node is positive with respect to the cathode.

A. Gate is negative and the anode is positive with respect to the cathode
B. Anode and the gate are both negative with respect to the cathode
C. Anode and the gate are both positive with respect to the cathode
D. Anode is negative and the gate is positive with respect to the cathode.

Ans: C

Q.5 Pulse gate triggering is achieved by means of

A. An LC circuit
B. A UJT relaxation oscillator circuit
C. A diac-triac circuit
D. A rheostatic arrangement

Ans: B


Q.6 RC triggering is preferred over resistance triggering because

A. Provides a large value of the triggering angle
B. Provides accurate triggering
C. Causes quick triggering
D. Protects the device from getting damaged

Ans: A

Q.7 The duration of the pulse in a pulse triggering system for scrs should be at least

A. 60 us
B. 40 us
C. 20 us
D. 10 us

Ans: C

Q.8 For thyristors, pulse triggering is preferred over dc triggering because

A. The gate dissipation is low
B. The pulse system is simpler
C. The triggering signal is required for a short duration
D. Of all of the above

Ans: A

Q.9 A snubber circuit is used in the scr control circuits to overcome the effects of

A. Transients in the dc supply
B. Corona
C. Electromagnetism
D. Heating caused by the high voltage ac supply

Ans: A

Q. 10 The function of a snubber circuit connected across an scr is to

A. Suppress dv/dt
B. Increase dv/dt
C. Decrease dv/dt
D. Keep transient voltage at a constant value

Ans: A

Thanks for reading

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