In an SCR, the anode current is controlled by gate current only external circuit

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Question
In an SCR, the anode current is controlled by
Options
A. gate current only
B. external circuit only
C. both gate current and external circuit
D. none of the above

Correct Answer

external circuit only

Explanation

Once SCR has been triggered the gate has no control. Only external resistance controls the anode current.

Power Electronics problems

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1. Which of these commutation methods uses an auxiliary SCR?
Options
A. Class A
B. Class B
C. Class C
D. Class D

2. In 180� mode of operation of a 3 phase bridge inverter, two thyristors conduct at one time.
Options
A. True
B. False

3. If t_on and t_off are the turn on and turn off times of a thyristor, then
Options
A. t_on and t_off are almost equal
B. t_on >> t_off
C. t_off >> t_on
D. t_on is about twice t_off

4. In a full wave converter (M - 2 connection) feeding an RLE load, the peak thyristor current is 15 A. For fully controlled bridge circuit and same load current, the peak thyristor current will be
Options
A. 30 A
B. 152 A
C. 15 A
D.

6. A single phase half wave controlled rectifier circuit has an R-L load. A freewheeling diode is also in the circuit. When freewheeling diode is conducting the SCR
Options
A. is forward biased
B. is reverse biased
C. may be forward biased or reverse biased
D. forward biased initially but reverse biased afterwards

7. A single phase semiconverter is feeding a highly inductive load. The circuit has a freewheeling diode across the load and firing angle is a. During one cycle of input voltage, the total duration of conduction of freewheeling diode is
Options
A. a
B. 2 a
C. 4 a
D. 0.5 a

9. The rated current of a thyristor is 40 A. The holding current will be about :
Options
A. 20 A
B. 1 A
C. 100 mA
D. 10 mA

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