Gate circuit or triggering circuit of a thyristor is

Related Mcqs:

1. For an SCR gate – cathode characteristic is a straight line of 130. For triggered source volume of 15 V and allowable gate power dissipation of 0.5 W compute the gate source resistance_____?

   A. 111.9 Ω.
   B. 11.19 Ω.
   C. 108 Ω.
   D. 115 Ω

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. 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

4. 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

5. Which triggering is the most reliable____________?

   A. Forward voltage triggering
   B. Gate triggering
   C. dV / dt triggering
   D. Thermal triggering

6. 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

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

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

8. 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

9. Typical range of thyristor turn OFF time is______________?

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

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