Number of PN junction in an SCR is____________?

Related Mcqs:

1. The turn-on time of an SCR with inductive load is 20 µs. The puls train frequency is 2.5 KHz with a mark/space ratio of 1/10, then SCR will___________?

   A. Turn on
   B. Not turn on
   C. Turn on if inductance is removed
   D. Turn on if pulse frequency us increased to two times

2. The typical value of SCR for modern alternator is____________?

   A. 1.5.
   B. 0.5.
   C. 1.0.
   D. 1.2.

3. The maximum di/dt in a SCR is____________?

   A. Directly proportional to supply voltage
   B. Directly proportional to inductance in the circuit
   C. Inversely proportional to supply voltage
   D. Both A and B

4. The capacitance of reversed bised junction J2 in a thyristor is CJ2 = 20 pF and can be assumed to be independant of the off state voltage. The limiting value of the charging current to turn on the thyristor is 16 mA. What is the critical value of dv/dt?

   A. 600 V/µs
   B. 800 V/µs
   C. 1200 V/µs
   D. 1000 V/µs

5. In BJT, the forward biased base emitter junction inject holes from base to emitter, the holes_______?

   A. Do not contribute to the collector current
   B. Result in net current flow component into the base
   C. Contribute to the collector current
   D. Only (a) and (b)
   E. Only (b) and (c)

6. An SCR is considered to be a semi controlled device because_______?

   A. it can be turned OFF but not ON with a gate pulse.
   B. it conducts only during one half cycle of an alternating current wave.
   C. it can be turned ON but not OFF with a gate pulse.
   D. it can be turned ON only during one half cycle of an AC.

7. SCR will be turned off when anode current is_______________?

   A. < latching current but greater than holding current and gate signal is 0.
   B. less than holding current.
   C. < latching current but greater than holding current and gate signal is present.
   D. both (A) and (B).

8. How can we protect SCR from thermal conditions _____________?

   A. Use of snubber circuit.
   B. Using heat sink.
   C. Using CB and fuse.
   D. Using equalizing circuit

9. Which of the following is used in SCR to protect from high dV / dt__________________?

   A. Snubber circuit
   B. Fuse
   C. Equalizing circuit
   D. Circuit breaker

10. A string of n parallel SCRs is operated at 72 KA, the rating of each SCR is 1 KA. If derating factor of the string is 0.1. value of n will be___________?

    A. 60
    B. 70
    C. 80
    D. 90