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?

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. 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

3. During which time maximum conduction spreading take place in the thyristor during turn ON?

   A. Delay time
   B. Spread time
   C. Rise time
   D. Same for every case

4. Typical range of thyristor turn OFF time is______________?

   A. 3 – 10 µs
   B. 3 – 50 µs
   C. 3 – 100 µs
   D. 3 – 500 µs

5. 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

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

   A. 0.01 A.
   B. 0.002 A.
   C. 0.009 A.
   D. 0.004 A.

7. 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)

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. If the anode current is 800 A, then the amount of current required to turn off the GTO is about____________?

   A. 20 A
   B. 200 A
   C. 600 A
   D. 400 A

10. A step up chopper has input voltage 110 V and output voltage 150 V. The value of duty cycle is_____?

    A. 0.32
    B. 0.67
    C. 0.45
    D. 0.27