If all the SCR’s of 3 phase PAC is replaced by diodes, they would be triggered_____________?

Related Mcqs:

1. For commutation in three phase PAC, normally balanced three phase voltages VR, VY and VB are connected to the three legs of the converter via______________?

   A. Three inductances
   B. Three capacitances
   C. Three resistance
   D. Three transistors

2. The turn-on time of an SCR with inductive load is 20 µs. The puls train frequency is 2.5 KHz with a mark/space ratio of 1/10, then SCR will___________?

   A. Turn on
   B. Not turn on
   C. Turn on if inductance is removed
   D. Turn on if pulse frequency us increased to two times

3. In commutation PAC stands for_______?

   A. Permanent angle converter
   B. Phase angle converter
   C. Phase angle commutation
   D. Phase and commutation

4. Which of the following is disadvantage of fast recovery diodes?

   A. Recovery is only 5 µs
   B. Recovery is only 50 µs
   C. Doping is carried out
   D. None of these

5. In a 3 phase CSI, if the required line output voltages are balanced and 120 degree out of phase, then the chopping angles are used to eliminate only the harmonics at frequencies

   A. 5
   B. 7
   C. 11
   D. All of these

6. n a phase controlled 3 phase ac voltage controller, the harmonic present is__________?

   A. 2nd
   B. 3rd
   C. 5th
   D. 7th

7. 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

8. 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

9. An SCR is made up of silicon because?

   A. silicon has large leakage current than germanium
   B. silicon has small leakage current than germanium
   C. silicon has small leakage voltage than germanium
   D. silicon has large leakage voltage than germanium

10. With gate open, the maximum anode current at which SCR is turned off from ON condition is called____________?

    A. breakdown voltage
    B. peak reverse voltage
    C. holding current
    D. latching current