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ECE :: Power Electronics

  1. A 3 phase fully controlled bridge converter is fed by a 3 phase system having phase voltage v = Vm sin ωt. The firing angle is a. The dc output voltage is


  2. Which of these commutation methods uses an external pulse for commutation?

  3. A.
    Class A
    B.
    Class C
    C.
    Class E
    D.
    Class F

  4. In a single phase full wave regulator feeding an R-L load, the power factor angle of load is θ. The range of control of firing angle a is

  5. A.
    0 ≤ ap
    B.
    θ ≤ ap
    C.
    0 ≤ a ≤ (p - θ)
    D.
    θ ≤ a ≤ (p + θ)

  6. A separately excited dc motor is run from a dc source through a chopper. At 600 rpm and rated torque, the duty cycle of chopper is 0.8. At 600 rpm and half the rated torque, the duty cycle is likely to be

  7. A.
    0.9
    B.
    0.8
    C.
    0.75
    D.
    0.6

  8. A relaxation oscillator uses

  9. A.
    tunnel diode
    B.
    UJT
    C.
    both tunnel diode and UJT
    D.
    PIN diode

  10. In a 3 phase bridge inverter with 180° mode of operation the numbers of thyristors conducting at one time are

  11. A.
    1
    B.
    2
    C.
    3
    D.
    4

  12. A single phase full converter can operate in

  13. A.
    4 quadrants
    B.
    3 quadrants
    C.
    2 quadrants
    D.
    1 quadrant

  14. In a 3 phase semiconverter, the freewheeling diode comes into operation only if firing angle

  15. A.
    is zero
    B.
    is 60°
    C.
    is more than 60°
    D.
    is more than 90°

  16. In the circuit of figure, the load current when thyristor is off

  17. A.
    is constant
    B.
    increases exponentially
    C.
    decreases exponentially
    D.
    zero

  18. A full bridge inverter is fed by a battery of 30 V. The rms value of output voltage is

  19. A.
    15 V
    B.
    152 V
    C.
    30 V
    D.
    302 V