4 thyristors rated 200 V in series. The operating voltage of the string is 600 V. Derating factor of the string is_____________________?

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. 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

3. 60 thyrsistors are connected in series and parallel to form a 10 KV and 5.5 KA switch. Each thyristor is rated for 1.2 KV, 1 KA. The no. of parallel path are 6. The efficiency of the switch is______________________?

   A. 76.3 %
   B. 91.6 %
   C. 83.3 %
   D. 90.9 %

4. A single phase one pulse controlled circuit has a resistance R and counter emf E load 400 sin(314 t) as the source voltage. For a load counter emf of 200 V, the range of firing angle control is _____?

   A. 30° to 150°.
   B. 30° to 180°.
   C. 60° to 120°.
   D. 60° to 180°.

5. 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

6. 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

7. Under over voltage condition impedance offered by the voltage clamping device is__________?

   A. low
   B. High
   C. moderate
   D. infinity

8. Under normal operating condition voltage clamping device offers impedance of_________?

   A. high value.
   B. low value.
   C. zero value.
   D. moderate value.

9. SCRs are used in series to meet_______________?

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

10. For series connected SCR’s dynamic equalising circuit consists of___________?

    A. R and C in series but with diode across C
    B. R and C in series but with diode across R
    C. Series R and diode with C across R
    D. Series R and diode with C across R