Uncontrolled Rectifier MCQ

1. A half-wave rectifier circuit using ideal diode has an input voltage of 20sinωt volt. Then average and RMS value of output voltage respectively are

  1. 10/π V and 10 V
  2. 20/π V and 5 V
  3. 20/π V and 10 V
  4. 10/π V and 5 V
Answer
Answer. c

2. The input power factor of the converter circuit may be defined as the ratio of

  1. total mean input power to the total rms input volt amperes.
  2. total rms input volt amperes to the total mean input power.
  3. total peak input volt amperes to the total rms input volt amperes.
  4. total input rms volt amperes to the total input peak volt amperes.
Answer
Answer. a

3. Compute the ripple factor of a single-phase full-wave rectifier with load resistance R = 10 kΩ. Forward bias dynamic resistance of diodes used is 100 Ω. The rms voltage across secondary winding is 330 V.

  1. 4.82
  2. 1.21
  3. 0.482
  4. 0.812
Answer
Answer. c

4. A single-phase two pulse converter feeds an R-L load with insufficient smoothing but the conduction is continuous. If the resistance of the load circuit is increased, then

  1. the ripple content of the load current will remain the same.
  2. the ripple content of the load current will decrease.
  3. the ripple content of the load current will increase.
  4. there is possibility of discontinuous conduction due to an increase in the ripple content.
Answer
Answer. d

5. The use of multiphase rectifier in place of single-phase rectifier results in

  1. Increased output voltage and reduced harmonics
  2. Increased output voltage and increased harmonics
  3. Decreased output voltage and reduced harmonics
  4. Increased output voltage and no effect on harmonics
Answer
Answer. a

6. The average output voltage of a fly-back converter is Vo = 24 V at a resistive load of R = 0.8 Ω. The duty cycle ratio is α = 50% and the switching frequency is f=1 kHz. The on-state voltage drop of transistors and diodes are V, = 1.2 V and Vd = 0.7 V respectively. The turn ratio of the transformer is ‘a’ = Ns/Np = 0.25. What is the efficiency of the converter?

  1. 86.5%
  2. 96%
  3. 75%
  4. 90%
Answer
Answer. b

7. Which one of the following statements is correct?

The function of the bleeder resistor in a power supply is

  1. to ensure a minimum current drain in the circuit
  2. to increase the output d.c. voltage
  3. to increase the output current
  4. same as that of a load resistor
Answer
Answer. a

8. The characteristic features of discontinuous conduction compared to continuous conduction in a two-pulse, single-phase bridge converter are

  1. larger average value of load voltage and larger ripple-content
  2. larger average value of load voltage and smaller ripple-content
  3. smaller average value of load voltage and smaller ripple-content
  4. smaller average value of load voltage and larger ripple-content
Answer
Answer. d

9. In a three-phase full-wave a.c. to d.c. converter, the ratio of output ripple-frequency to the supply voltage frequency is

  1. 2
  2. 3
  3. 6
  4. 12
Answer
Answer. c

10. The total harmonic distortion (THD) of ac supply input current of rectifiers is maximum for

  1. single-phase diode rectifier with dc inductive filter
  2. 3-phase diode rectifier with dc inductive filter
  3. 3-phase thyristor rectifier with inductive filter
  4. single-phase diode rectifier with capacitive filter
Answer
Answer. d
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