To meet high current demand we use SCRs in______________?

Related Mcqs:

1. 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

2. Practical way of obtaining static voltage equalization in series connected SCRs is by the use of____________?

   A. One resistor across the string
   B. Resistors of the same value across each SCR
   C. Resistors of different values across each SCR
   D. One resistor in series with each SCR

3. SCRs are used in series to meet_______________?

   A. high current demand
   B. low voltage demand
   C. low current demand
   D. high voltage demand

4. 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

5. The transfer function of PWM is generally developed in______________?

   A. Time domain
   B. Frequency domain
   C. Either A. or B.
   D. None of these

6. 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.

7. 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.

8. 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

9. 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)

10. The reverse recovery time of diode is trr = 3 μs and the rate off all of the diode current is di/dt = 30 A/μs. The storage charge current QRR is___________?

    A. 130 μs
    B. 135 μs
    C. 140 μs
    D. 145 μs