Typical range of thyristor turn OFF time is______________?

Related Mcqs:

1. 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

2. 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)

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. A thyristor is basically________?

   A. PNPN device
   B. A combination of diac and triac
   C. A set of SCRs
   D. A set if SCR,diac and triac

5. Thyristor can be protected from over voltages by using

   A. 23 mA.
   B. 40 mA.
   C. 10 mA.
   D. 60 mA.

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. 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

8. Thyristor is nothing but a____________?

   A. Controlled transistor
   B. Controlled switch
   C. Amplifier with higher gain
   D. Amplifier with large current gain

9. What is used to protect a thyristor from high di / dt conditions__________?

   A. Fuse.
   B. Snubber circuit
   C. Inductor
   D. Voltage clamping device

10. 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