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ECE :: Power Electronics

  1. UJT can be used for

  2. A.
    firing an SCR
    B.
    turning off an SCR
    C.
    both firing and turning off an SCR
    D.
    none of the above

  3. In a series inverter supplying a load resistance R, the commutating elements L and C should be such that


  4. In a full wave converter (M - 2 connection) feeding an RLE load, the peak thyristor current is 15 A. For fully controlled bridge circuit and same load current, the peak thyristor current will be

  5. A.
    30 A
    B.
    152 A
    C.
    15 A
    D.

  6. Induction heating systems require low frequency inverters.

  7. A.
    True
    B.
    False

  8. A single phase half wave controlled rectifier circuit is feeding on RL load. The circuit has a freewheeling diode. The input voltage is v = Vm sin ωt. If I0 is the load current during the conduction of freewheeling diode, the KVL equation during the conduction of free wheeling diode is


  9. HVDC transmission systems generally use

  10. A.
    12 pulse converters
    B.
    6 pulse converters
    C.
    3 pulse converters
    D.
    either 12 or 6 pulse converters

  11. A single phase semiconverter is feeding a highly inductive load. The circuit has a freewheeling diode across the load and firing angle is a. During one cycle of input voltage, the total duration of conduction of freewheeling diode is

  12. A.
    a
    B.
    2 a
    C.
    4 a
    D.
    0.5 a

  13. During forward blocking state of SCR, the voltage and current respectively are

  14. A.
    high and high
    B.
    low and low
    C.
    high and low
    D.
    low and high

  15. In a 3 phase full converter the average load current is 150 A. The average thyristor current is

  16. A.
    150 A
    B.
    75A
    C.
    50 A
    D.
    25 A

  17. The two modes of operation of three phase bridge inverters are known as

  18. A.
    60° mode and 120° mode
    B.
    90° mode and 120° mode
    C.
    120° mode and 180° mode
    D.
    120° mode and 240° mode