If holding current of a thyristor is 2 mA then latching current should be_____?

Related Mcqs:

1. When a large surge current of very short duration flows through a thyristor then which one of the following device will operate to protect the thyristor ___________?

   A. CB
   B. Snubber circuit
   C. Voltage clamping device
   D. Fast acting current limiting device (FACL fuse)

2. 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

3. An SCR has half cycle surge current rating of 3000 A for 50 Hz supply. One cycle surge current will be_____?

   A. 1500 A.
   B. 6000 A.
   C. 2121.32 A.
   D. 4242.64 A.

4. Which statement is true for latching current ___________?

   A.It is related to turn off process of the device.
   B. It is related to conduction process of device.
   C. It is related to turn on process of the device.
   D. Both C and D.

5. The latching current of GTO should be of order

   A. 100 mA
   B. 500 mA
   C. 1 A
   D. 2 A

6. CB used for over current protection of thyristor operates when the fault current is__________?

   A. of long period
   B. of short duration
   C. both (A) and (B)
   D. neither (A) nor (B)

7. A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 KA. The voltage and current rating of available SCRs are 1800 V and 1000 A. For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be_____________?

   A. 5, 7
   B. 4, 6
   C. 7, 5
   D. 6, 4

8. Leakage current flows through the thyristor in_________?

   A. forward blocking mode
   B. reverse blocking mode
   C. both forward and reverse blocking mode
   D. forward conduction mode

9. Let of a thyristor Vc1, Vc2, Vc3 are forward break over voltage for gate current Ig1, Ig2, Ig3 respectively. Then________________?

   A. Vc1 > Vc2 > Vc3 when Ig1 > Ig2 > Ig3.
   B. Vc1 > Vc2 > Vc3 when Ig1 < Ig2 < Ig3.
   C. Vc1 = Vc2 = Vc3 any value of Ig.
   D. Vc1 > Vc2 > Vc3 when Ig1 ≥ Ig2 &Atil

10. Thyristor can be protected from over voltages by using____________?

    A. voltage clamping device.
    B. fuse.
    C. heat sink.
    D. snubber circuit.