MCQOPTIONS
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MCQOPTIONS
This section includes 78 Mcqs, each offering curated multiple-choice questions to sharpen your Power Electronics knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In MPM, the square wave is the ________ signal whereas the triangular wave is the ________ signal. |
| A. | reference, carrier |
| B. | base, reference |
| C. | carrier, reference |
| D. | none of the mentioned |
| Answer» B. base, reference | |
| 2. |
What is the maximum line voltage value in case of a three-phase VSI in 180° mode? |
| A. | 2Vs |
| B. | Vs |
| C. | 3Vs |
| D. | 2Vs/3 |
| Answer» C. 3Vs | |
| 3. |
A single phase full bridge inverter has RLC load with R = 4 Ω, L = 35 mH and C = 155 μF. The dc input voltage is 230 V and the output frequency is 50 Hz. Find the rms value of the fundamental load current. |
| A. | 28.31 A |
| B. | 20.02 A |
| C. | 16.69 A |
| D. | 26.90 A |
| Answer» C. 16.69 A | |
| 4. |
The harmonic factor of nth harmonic is given by |
| A. | Vn |
| B. | V1/Vn |
| C. | Vn/V1 |
| D. | None of the mentioned |
| Answer» D. None of the mentioned | |
| 5. |
The distortion factor (μ) is the ratio of |
| A. | total rms output voltage to fundamental rms output voltage |
| B. | fundamental rms output voltage to fundamental average output voltage |
| C. | total rms output voltage to rms value of all the harmonic components |
| D. | fundamental rms output voltage to total rms output voltage |
| Answer» E. | |
| 6. |
Let Vs be the amplitude of the output voltage and P be the output power for a single-phase half bridge inverter. Then the corresponding values for a full bridge inverter would be |
| A. | 2Vs, 4P |
| B. | 2Vs, 2P |
| C. | Vs, P |
| D. | 2Vs, P |
| Answer» B. 2Vs, 2P | |
| 7. |
Find the distortion factor (μ), for a single phase half wave bridge inverter with dc source Vs = 1 kV. |
| A. | 0.87 |
| B. | 1 |
| C. | 0.9 |
| D. | 0.7 |
| Answer» D. 0.7 | |
| 8. |
In case of the 120° mode of operation, __________ devices conduct at a time. |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | none of the mentioned |
| Answer» B. 3 | |
| 9. |
In case of MPM with two pulses per half cycle of width = d each and ɣ as the distance between the first pulse and ωt=0, for eliminating the nth harmonic from the output voltage, the value of gamma (ɣ) must be equal to |
| A. | 0 |
| B. | π |
| C. | π/n |
| D. | d/n |
| Answer» D. d/n | |
| 10. |
In PWM, the comparator output is further given to a ____________ |
| A. | integrator |
| B. | scr devices |
| C. | trigger pulse generator |
| D. | snubber circuit |
| Answer» D. snubber circuit | |
| 11. |
If Vr is the rms value of the inverter output voltage and V1 is the rms value of the fundamental component, then the total harmonic distortion (THD) is given by |
| A. | Vr/V1 |
| B. | (Vr + V1r |
| C. | [ (Vr/V1)2 – 1 ]1/2 |
| D. | [ (Vr/V1)1/2 + 1 ]2 |
| Answer» D. [ (Vr/V1)1/2 + 1 ]2 | |
| 12. |
Single-phase full bridge inverters requires |
| A. | 4 SCRs and 2 diodes |
| B. | 4 SCRs and 4 diodes |
| C. | 2 SCRs and 4 diodes |
| D. | 2 SCRs and 2 diodes |
| Answer» C. 2 SCRs and 4 diodes | |
| 13. |
For a full bridge inverter with the following load: R = 2 Ω, XL = 8 Ω and XC = 6 Ω. |
| A. | The output voltage lags the current by 45° |
| B. | The output current lags the voltage by 45° |
| C. | The output current lags the voltage by 90° |
| D. | The output current lags the voltage by more than 90° |
| Answer» C. The output current lags the voltage by 90° | |
| 14. |
In a PWM inverter, if the frequency of the lowest harmonic is 180 Hz, then the frequency of the fundamental component would be ___________ |
| A. | 50 Hz |
| B. | 60 Hz |
| C. | 540 Hz |
| D. | 90 Hz |
| Answer» C. 540 Hz | |
| 15. |
A single phase full bridge inverter is fed from a dc source such that the fundamental component of output voltage = 230 V. Find the rms value of SCR and diode current respectively, for a R load of 2 Ω. |
| A. | 115 A, 80 A |
| B. | 81.33 A, 36.2 A |
| C. | 36.2 A, 0 A |
| D. | 81.33 A, 0 A |
| Answer» E. | |
| 16. |
If T1 is gated at 0 °, T3 and T5 will start conducting at _______ and _________ respectively. |
| A. | 180°, 270° |
| B. | 120°, 240° |
| C. | 180°, 300° |
| D. | 240°, 360° |
| Answer» C. 180°, 300° | |
| 17. |
What is the peak value of phase voltage in case of 3-phase VSI with 180° mode. The supply side consists of a constant dc voltage source of Vs. |
| A. | Vs |
| B. | 3Vs/2 |
| C. | 2Vs/3 |
| D. | 3Vs |
| Answer» D. 3Vs | |
| 18. |
Calculate the pulse width in case of MPM, if the amplitudes of square wave and triangular wave are respectively 2 V and 3 V respectively. 16 pulses per cycle are generated. |
| A. | 18° |
| B. | 7.5° |
| C. | 6.4° |
| D. | 9° |
| Answer» C. 6.4° | |
| 19. |
In case of a single-pulse width modulation with the pulse width = 2d, to eliminate the 3rd harmonic from the output voltage waveform, the value of the pulse width (2d) must be |
| A. | 0° |
| B. | 60° |
| C. | 120° |
| D. | 180° |
| Answer» D. 180° | |
| 20. |
The 120° mode of operation of a three phase bridge inverter requires ___________ number of steps. |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» D. 8 | |
| 21. |
The McMurray-Bedford half-bridge inverter requires |
| A. | 4 SCRs, 2 diodes, 2 capacitors and 2 inductors |
| B. | 4 SCRs, 4 diodes, 2 capacitors and 2 inductors |
| C. | 2 SCRs, 4 diodes, 2 capacitors and 1 inductor |
| D. | 2 SCRs, 2 diodes, 2 capacitors and 2 inductors |
| Answer» E. | |
| 22. |
The fundamental component of output voltage for a full wave bridge inverter is given by |
| A. | (2Vs/π) sinωt |
| B. | (4Vs/π) sinωt |
| C. | (Vs/2π) sinωt |
| D. | (Vs) |
| Answer» C. (Vs/2π) sinωt | |
| 23. |
In the multiple-pulse width modulation method, the Fourier coefficient an is |
| A. | (Vs/π) [ cos(nπ/2) cos(nd) ]. |
| B. | 0 |
| C. | (4Vs/nπ) [sin(nπ/2) sin(n |
| D. | ].d) (2Vs/nπ) [sin(nπ/2) sin(nd)]. |
| Answer» C. (4Vs/nπ) [sin(nπ/2) sin(n | |
| 24. |
A single phase full bridge inverter using transistors and diodes is feeding a R load of 3 Ω with the dc input voltage of 60 V. Find the rms output voltage and the peak reverse blocking voltage of each transistor. |
| A. | 30 V, 60 V |
| B. | 30 V, 30 V |
| C. | 60 V, 60 V |
| D. | 60 V, 30 V |
| Answer» D. 60 V, 30 V | |
| 25. |
A single-phase bridge inverter, fed from a 230 V dc is connected to the load R = 10 Ω and L = 0.03 H. The output is a quasi-square wave with an on period of 0.5 of a cycle. Determine the fundamental component of rms output voltage. |
| A. | 207.10 V |
| B. | 146.42 V |
| C. | 265.4 V |
| D. | 129 V |
| Answer» C. 265.4 V | |
| 26. |
____________ is the measure of the contribution of any individual harmonic to the inverter output voltage. |
| A. | THD |
| B. | Distortion Factor |
| C. | Harmonic Factor |
| D. | TUF |
| Answer» D. TUF | |
| 27. |
A single phase full bridge inverter circuit, has load R = 2 Ω and dc source Vs = 230 V. Find the value of power delivered to the load in watts only due to the fundamental component of the load current. |
| A. | 5361.5 W |
| B. | 2142.5 W |
| C. | 21424.5 W |
| D. | 214.2 W |
| Answer» D. 214.2 W | |
| 28. |
A single phase full bridge inverter has RLC load with R = 4 Ω, Xl = 11 Ω and Xc = 20.54 Ω. The dc input voltage is 230 V. Find the value of fundamental load power. |
| A. | 1633 W |
| B. | 1603 W |
| C. | 1576 W |
| D. | none of the mentioned |
| Answer» C. 1576 W | |
| 29. |
Determine the distortion factor (μ) for a full bridge inverter with supply Vs = 60 V. |
| A. | 0.8 |
| B. | 0.7 |
| C. | 0.9 |
| D. | 1 |
| Answer» D. 1 | |
| 30. |
In an inverter, if the fundamental output frequency is 50 Hz, then the frequency of the lowest order harmonic will be |
| A. | 50 Hz |
| B. | 150 Hz |
| C. | 250 Hz |
| D. | 350 Hz |
| Answer» C. 250 Hz | |
| 31. |
A single phase half bridge inverter has load R = 2 Ω and a dc voltage source Vs/2 = 115 V. Find the power delivered to the load due to the fundamental component. |
| A. | 536 kW |
| B. | 53.61 kW |
| C. | 5.361 kW |
| D. | 536 W |
| Answer» D. 536 W | |
| 32. |
In case of a single-pulse width modulation with the pulse width = 2d, to eliminate the nth harmonic from the output voltage |
| A. | d = π |
| B. | 2d = π |
| C. | nd = π |
| D. | nd = 2π |
| Answer» D. nd = 2π | |
| 33. |
A single phase half bridge inverter has RLC load. The dc input voltage (Vs/2) = 115 V and the output frequency is 50 Hz. The expression for the load voltage up to the fifth harmonic will be given by |
| A. | 146 sin 314t + 48.81 sin 314t + 58.57 sin 318t + 28.31 sin 318t + 3.686 sin 318t |
| B. | 146 sin 314t + 48.81 sin (3 x 314t) + 29.28 sin (5 x 318t) |
| C. | 146 sin 314t + 48.81 sin (2 x 314t) + 58.57 sin (3 x 318t) |
| D. | none of the mentioned |
| Answer» C. 146 sin 314t + 48.81 sin (2 x 314t) + 58.57 sin (3 x 318t) | |
| 34. |
The total harmonic distortion (THD) is the measure of |
| A. | input vs output power factor |
| B. | temperature sensitivity |
| C. | waveform distortion |
| D. | contribution of each harmonic to the total output |
| Answer» D. contribution of each harmonic to the total output | |
| 35. |
In the 180° mode VSI, ___________ devices conduct at a time. |
| A. | 5 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» D. 4 | |
| 36. |
The single-phase McMurray-Bedford type bridge inverter is a/an |
| A. | auxiliary-commutated inverter |
| B. | complementary-commutated inverter |
| C. | supplementary-commutated inverter |
| D. | none of the mentioned |
| Answer» C. supplementary-commutated inverter | |
| 37. |
In single-phase modulation of PWM inverters, the lowest harmonic can be eliminated if the pulse width is made equal to __________ |
| A. | 30° |
| B. | 0° |
| C. | 120° |
| D. | 60° |
| Answer» D. 60° | |
| 38. |
In the multiple-pulse width modulation method with two pulses per half cycle of width = d each and ɣ as the distance between the first pulse and ωt=0, has the Fourier coefficient bn = |
| A. | (8Vs/π) [ cos(ɣπ/2) cos(nd/2) ]. |
| B. | 0 |
| C. | (4Vs/nπ) [sin(nɣ) sin(nd/2)]. |
| D. | (8Vs/nπ) [sin(nɣ) sin(nd/2)]. |
| Answer» E. | |
| 39. |
In an inverter, if the fundamental output frequency is 45 Hz, then the frequency of the lowest order harmonic will be |
| A. | 45 Hz |
| B. | 225 Hz |
| C. | 15 Hz |
| D. | 135 Hz |
| Answer» E. | |
| 40. |
By controlling the modulation index (MI), __________ can be controlled. |
| A. | gain |
| B. | output frequency |
| C. | harmonic content of the output voltage |
| D. | cosine component of the output voltage |
| Answer» D. cosine component of the output voltage | |
| 41. |
In case of MPM with two pulses per half cycle of width = d each and ɣ as the distance between the first pulse and ωt=0, for eliminating the nth harmonic from the output voltage, which of the following condition must be satisfied? |
| A. | d = 2π |
| B. | d = π |
| C. | d = n° |
| D. | d = 2π/n |
| Answer» E. | |
| 42. |
A single-phase half bridge inverter is connected to a 230 V dc source which is feeding a R load of 10 Ω. Determine the fundamental power delivered to the load. |
| A. | 1.07 W |
| B. | 107.2 W |
| C. | 1.07 kW |
| D. | 107.2 kW |
| Answer» D. 107.2 kW | |
| 43. |
In the MPM method, the comparator is given _______ and _______ types of waveform at its input. |
| A. | square, sine |
| B. | square, quasi-square |
| C. | sine, triangular |
| D. | square, triangular |
| Answer» E. | |
| 44. |
The peak value of the line voltage in case of 120° mode of operation of a three-phase bridge inverter is |
| A. | Vs/2 |
| B. | 3Vs/2 |
| C. | Vs/√2 |
| D. | Vs |
| Answer» E. | |
| 45. |
The HF (Harmonic factor of nth harmonic) is the ratio of |
| A. | an average and a rms value |
| B. | a rms and an average value |
| C. | two volt-ampere values |
| D. | two rms values |
| Answer» E. | |
| 46. |
VSIs using IGBTs are turned off by |
| A. | load commutation |
| B. | line commutation |
| C. | applying a negative gate pulse |
| D. | removing the base signal |
| Answer» E. | |
| 47. |
Force-commutated CSIs need |
| A. | capacitors for their commutation |
| B. | inductors for their commutation |
| C. | diodes for their commutation |
| D. | none of the mentioned |
| Answer» B. inductors for their commutation | |
| 48. |
In the sinusoidal pulse width modulation, ____________ is the reference wave signal. |
| A. | square wave |
| B. | triangular wave |
| C. | sinusoidal wave |
| D. | quasi-square wave |
| Answer» D. quasi-square wave | |
| 49. |
Single phase half bridge inverters requires |
| A. | two wire ac supply |
| B. | two wire dc supply |
| C. | three wire ac supply |
| D. | three wire dc supply |
| Answer» E. | |
| 50. |
A single phase full bridge inverter using transistors and diodes is feeding a R load of 3 Ω with the dc input voltage of 60 V. Find the fundamental frequency output power. |
| A. | 1200 W |
| B. | 856 W |
| C. | 972 W |
| D. | 760 W |
| Answer» D. 760 W | |