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

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. SCRs are used in series to meet_______________?

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

3. To meet high current demand we use SCRs in______________?

   A. series connection.
   B. parallel connection.
   C. anti parallel connection.
   D. both B and C.

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. 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

6. 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 %

7. Voltage commutation circuit can be converted into a current commutation by interchanging the positions of____________?

   A. Diode and capacitor
   B. Capacitor and SCR
   C. Inductor and capacitor
   D. Capacitor and load

8. 4 thyristors rated 200 V in series. The operating voltage of the string is 600 V. Derating factor of the string is_____________________?

   A. 0.75
   B. 0.7
   C. 0.2
   D. 0.25

9. 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

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

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