Explore topic-wise MCQs in Power Electronics.

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.

51.

In the single-pulse width modulation method, the Fourier coefficient an is given by

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
Discussion
52.

Which of the following is not a PWM technique?

A. Single-pulse width modulation
B. Multiple-pulse width modulation
C. Triangular-pulse width modulation
D. Sinusoidal-pulse width modulation
Answer» D. Sinusoidal-pulse width modulation
Discussion
53.

In case of sinusoidal pulse width modulation with MI < 1, if the number of pulses per half cycle (N) = 6, then

A. harmonics of order 7 and 9 become significant
B. harmonics of order 7 and 9 are eliminated
C. harmonics of order 11 and 13 become significant
D. harmonics of order 11 and 13 are eliminated
Answer» D. harmonics of order 11 and 13 are eliminated
Discussion
54.

The amplitude of the nth harmonic of the two-pulse MPM waveform is given by __________Let d be the width of a single pulse and ɣ be the distance from 0 to the centre of the first pulse.

A. (8Vs/nπ) sin(nɣ) sin(nd/2)
B. (4Vs/nπ) sin(nɣ) sin(nd/2)
C. (8Vs/nπ) sin(nπ) sin(nd/2)
D. (8Vs/nπ) sin(nɣ/2) sin(nd/2)
Answer» B. (4Vs/nπ) sin(nɣ) sin(nd/2)
Discussion
55.

In VSI (voltage source inverters)

A. both voltage and current depend on the load impedance
B. only voltage depends on the load impedance
C. only current depends on the load impedance
D. none of the mentioned
Answer» D. none of the mentioned
Discussion
56.

In the PWM method

A. external commutating capacitors are required
B. more average output voltage can be obtained
C. lower order harmonics are minimized
D. higher order harmonics are minimized
Answer» D. higher order harmonics are minimized
Discussion
57.

The modulation index (MI) is given byVr = peak value of the reference wave.Vc = peak value of the carrier wave.

A. Vr/Vc
B. Vc/Vr
C. (1 + Vc/Vr)
D. 1/(Vc Vr)
Answer» B. Vc/Vr
Discussion
58.

A single phase full bridge inverter has RLC load. The dc input voltage is 230 V and the output frequency is 50 Hz. Find the expression for the load voltage up to the fifth harmonic.

A. 292 sin 314t + 97.62 sin 314t + 58.57 sin 318t + 28.31 sin 318t + 3.686 sin 318t
B. 292 sin 314t + 97.62 sin (3 x 314t) + 58.57 sin (5 x 318t)
C. 292 sin 314t + 97.62 sin (2 x 314t) + 58.57 sin (3 x 318t) + 28.31 sin (4 x 318t) + 3.686 sin (5 x 318t)
D. 292 sin 512t + 25.62 sin 249t + 6.74 sin 508t
Answer» C. 292 sin 314t + 97.62 sin (2 x 314t) + 58.57 sin (3 x 318t) + 28.31 sin (4 x 318t) + 3.686 sin (5 x 318t)
Discussion
59.

Find the peak value of the fundamental component of voltage with a pulse width of 2d = 90 and Vs = 240 V for single-pulse modulation in a full wave bridge inverter.

A. 305 V
B. 216 V
C. 0 V
D. 610 V
Answer» C. 0 V
Discussion
60.

A single-phase bridge inverter, fed from a 230 V dc is connected to the load R = 10 Ω and L = 0.03 H. Determine the fundamental component of rms output current. Fundamental output frequency of the square wave output = 50 Hz.

A. 30 A
B. 15 A
C. 2.3 A
D. 20.7 A
Answer» C. 2.3 A
Discussion
61.

The waveform obtained by __________ is more near to a sinusoidal wave

A. PWM inverters
B. Stepped wave inverters
C. parallel connected inverters
D. None of the mentioned
Answer» C. parallel connected inverters
Discussion
62.

A single phase half bridge inverter has a dc voltage source Vs/2 = 115 V. Find the rms value of the fundamental component of output voltage.

A. 510 V
B. 103.5 V
C. 120 V
D. 96 V
Answer» C. 120 V
Discussion
63.

In single-phase modulation of PWM inverters, the 5th order harmonic can be eliminated if the pulse width is made equal to ___________

A. 30°
B. 36°
C. 72°
D. None of the mentioned
Answer» D. None of the mentioned
Discussion
64.

In pulse width modulation

A. the output voltage is modulated
B. the input voltage is modulated
C. the gating pulses are modulated
D. none of the mentioned
Answer» D. none of the mentioned
Discussion
65.

The Total Harmonic Distortion (THD) is the ratio of

A. rms value of all the harmonic components to the rms value of the fundamental component
B. average value of all the harmonic components to the rms value of the fundamental component
C. rms value of all the third harmonic component to the rms value of the fundamental component
D. rms value of all the fundamental component to the rms value of all the harmonic components
Answer» B. average value of all the harmonic components to the rms value of the fundamental component
Discussion
66.

In the single-pulse width modulation method, the Fourier coefficient bn is given by

A. (Vs/π) [ sin(nπ/2) sin(nd) ].
B. 0
C. (4Vs/nπ) [sin(nπ/2) sin(n
D. ].d) (2Vs/nπ) [sin(nπ/2) sin(nd)].
Answer» D. ].d) (2Vs/nπ) [sin(nπ/2) sin(nd)].
Discussion
67.

In a 3-phase VSI operating in square-wave mode, the output line voltage is free from

A. 3rd harmonic
B. 7th harmonic
C. 11th harmonic
D. 13th harmonic
Answer» B. 7th harmonic
Discussion
68.

The output current wave of a single-phase full bridge inverter on RL load is

A. a sine wave
B. a square wave
C. a triangular wave
D. constant dc
Answer» D. constant dc
Discussion
69.

In current source inverters

A. L filter is used after the CSI (load side)
B. L filter is used before the CSI (input side)
C. C filter is used after the CSI (load side)
D. C filter is used before the CSI (input side)
Answer» C. C filter is used after the CSI (load side)
Discussion
70.

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 angle by which the third harmonic current will lead/lag the third harmonic output voltage.

A. 67.25°
B. 96.4°
C. 49.87°
D. 81.3°
Answer» E.
Discussion
71.

In a single-phase half wave inverter ________ SCR(s) are/is gated at a time.

A. one
B. two
C. three
D. none of the mentioned
Answer» B. two
Discussion
72.

In a single phase full wave bridge inverter, when the output is Vs or -Vs

A. one SCR and one diode are conducting
B. four SCRs are conducting
C. two SCRs are conducting
D. two diodes are conducting
Answer» D. two diodes are conducting
Discussion
73.

In the single-pulse width modulation method, when the pulse width of 2d is equal to its maximum value of π radians, then the fundamental component of output voltage is given by

A. Vs
B. 4Vs/π
C. 0
D. 2Vs/π
Answer» C. 0
Discussion
74.

A single phase full bridge inverter has load R = 2 Ω, and dc voltage source Vs = 230 V. Find the rms value of the fundamental load current.

A. 96 A
B. 0 A
C. 103 A
D. none of the mentioned
Answer» D. none of the mentioned
Discussion
75.

In single-phase modulation of PWM inverters, the pulse width is 120°. For an input voltage of 220 V dc, the rms value of output voltage is

A. 185 V
B. 254 V
C. 127 V
D. 179 V
Answer» E.
Discussion
76.

In current source inverters (CSIs), the output voltage's

A. amplitude depends upon the load impedance
B. waveform depends upon the load impedance
C. amplitude as well as the nature of the waveform depends on the load
D. both amplitude and waveform are independent of the load impedance
Answer» D. both amplitude and waveform are independent of the load impedance
Discussion
77.

A single phase half bridge inverter has load R = 2 Ω and a dc voltage source Vs/2 = 115 V. Find the rms value of the fundamental load current.

A. 10.25 A
B. 51.7 A
C. 86 A
D. 24.8 A
Answer» C. 86 A
Discussion
78.

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 average current through each SCR inverter switch.

A. 11.5 A
B. 5.75 A
C. 23 A
D. none of the mentioned
Answer» C. 23 A
Discussion