Power Electronics Inverter MCQ

1. A single-phase, voltage source, square wave inverter feeds a pure inductive load. The waveform of the current will be

  1. triangular
  2. trapezoidal
  3. rectangular
  4. sinusoidal
Answer. a

2. In the sinusoidal pulse-width modulation scheme, if the zero of the triangular wave coincides with the zero of the reference sinusoidal, then the number of pulse per half cycle is

\\a. \frac{f_c}{2f}\\ \\ b. \frac{f_c}{2f}+1\\ \\ c. \frac{2f_c}{f}\\ \\ d. \frac{f_c}{2f}-1

Answer. d

3. In a single-phase full bridge inverter what is the advantages of a unipolar switching over the bipolar switching?

  1. Apparent doubling of the switching frequency
  2. elimination of 5th and 7th harmonics
  3. increase of the fundamental component by a factor of 115 for the same DC input voltage
  4. none of the above
Answer. a

4. A voltage source inverter is used when source and load inductances are respectively

  1. small and small
  2. large and large
  3. large and small
  4. small and large
Answer. d

5. For a 1-phase full-bridge inverter fed from 48 V dc and connected to load resistance of 2.4 Ω, the RMS value of fundamental component of output voltage is

  1. 43.2 V
  2. 34.4 V
  3. 21.6 V
  4. 20 V
Answer. a

6. A voltage source inverter (VSI) is normally employed when

  1. both source inductance and load inductance are large
  2. both source inductance and load inductance are small
  3. source inductance is small and load inductance is large
  4. source inductance is large and load inductance is small
Answer. c

7. In a single-phase VSI bridge inverter, the load current is Io = 200sin(ωt – 45°) mA. The d.c. supply voltage is 220 V. What is the power drawn from the supply?

  1. 34.03 W
  2. 27.25 W
  3. 19.8 W
  4. 9.8 W
Answer. c

8. A single-phase full bridge inverter is connected to a load of 2.4 Ω. The d.c. input voltage is 48 V. What is the r.m.s. output at fundamental frequency?

\\a. \frac{4\times 48}{\sqrt{2}\pi } V\\ \\ b. \frac{2\times 48}{\sqrt{2}\pi } V\\ \\ c. \frac{4\times 48}{\pi } V\\ \\ d. \frac{2\times 48}{\pi } V

Answer. a

9. A single-phase half-bridge inverter has input voltage of 48 V DC. Inverter is feeding a load of 2.4 Ω. The RMS output voltage at fundamental frequency is

\\a. \frac{4\times 48}{\sqrt{2}\pi } V\\ \\ b. \frac{2\times 48}{\sqrt{2}\pi } V\\ \\ c. \frac{4\times 48}{\pi } V\\ \\ d. \frac{2\times 48}{\pi } V

Answer. b

10. Which one of the following statements is correct?

A voltage source inverter is normally employed

  1. when both the source and load have low values of impedance and reactance respectively.
  2. when both the source and load have high values of impedance and reactance respectively.
  3. when the source has high impedance and load has low reactance
  4. when the source has low impedance and load has high reactance
Answer. d

11. A single-phase inverter has square wave output voltage. What is the percentage of the fifth harmonic component in relation to the fundamental component?

  1. 10%
  2. 20%
  3. 30%
  4. 40%
Answer. b

12. Compared to a single-phase half-bridge inverter, the output power of a single-phase full-bridge inverter is higher by a factor of

  1. 2
  2. 8
  3. 4
  4. 12
Answer. c

13. In case of voltage source inverter, free-wheeling can be needed for the load of

  1. back emf nature
  2. resistive nature
  3. capacitive nature
  4. inductive nature
Answer. d

14. The main application of multilevel inverter is in

  1. voltage regulator
  2. synchronous buck converter
  3. dc motor drive
  4. reactive power compensation
Answer. d

15. Current source inverters are suitable for supply power to

  1. RL loads
  2. Inductive loads
  3. Capacitive loads
  4. All loads
Answer. c

16. A current source inverter is obtained by inserting a large

  1. capacitance in series with dc supply
  2. inductance in parallel with dc supply
  3. capacitance in parallel with dc supply
  4. inductance in series with dc supply
Answer. a

17. A single-phase current source inverter is connected with capacitive load only the waveform of the output voltage across the capacitor for constant source current will be

  1. step function
  2. triangular wave
  3. square wave
  4. sine wave
Answer. b

18. In 3-phase inverter with 180° conduction mode the number of switches that is on at any instant of time is

  1. 4
  2. 3
  3. 2
  4. 1
Answer. b

19. What is the region of operation of a 3-phase inverter employing sinusoidal PWM when the peak-to-peak values of both the carrier and the modulating waves are made equal?

  1. six-step operation
  2. boundary of linear modulation and over modulation
  3. over modulation
  4. linear modulation
Answer. d

20. What should be the frequency modulation ratio (mf) for a 3-phase inverter, if the mfth harmonic and its odd multiples are to be suppressed in the line-to-line voltages?

  1. mf should be odd
  2. mf should be even
  3. mf should be an odd multiple of 3
  4. mf should be an even multiple of 3
Answer. c
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