# in the single-pulse width modulation method, the output voltage waveform is symmetrical about

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## 250+ TOP MCQs on PWM Inverters

Power Electronics Multiple Choice Questions on “PWM Inverters-1”. 1. In the single-pulse width modulation method, the output voltage waveform is

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## 250+ TOP MCQs on PWM Inverters-1 and Answers

Power Electronics Multiple Choice Questions on “PWM Inverters-1”.

1. In the single-pulse width modulation method, the output voltage waveform is symmetrical about __________

A. π B. 2π C. π/2 D. π/4 Answer: C

Clarification: The waveform is a positive in the first half cycle and symmetrical about π/2 in the first half.

2. In the single-pulse width modulation method, the output voltage waveform is symmetrical about ____________ in the negative half cycle.

A. 2π B. 3π/2 C. π/2 D. 3π/4 Answer: B

Clarification: In the negative half the wave is symmetrical about 3π/2.

3. The shape of the output voltage waveform in a single PWM is

A. square wave B. triangular wave

C. quasi-square wave

D. sine wave Answer: C

Clarification: Positive and the negative half cycles of the output voltage are symmetrical about π/2 and 3π/2 respectively. The shape of the waveform obtained is called as quasi-square wave.

4. 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(nD.].

D. (2Vs/nπ) [sin(nπ/2) sin(nD.].

Answer: C

Clarification: The Fourier analysis is as under:

bn = (2/π) ∫ Vs sin nωt .d(ωt) , Where the integration would run from (π/2 + D. to (π/2 – D.

2d is the width of the pulse.

5. 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(nD.].

D. (2Vs/nπ) [sin(nπ/2) sin(nD.].

Answer: B

Clarification: As the positive and the negative half cycles are identical the coefficient an = 0.

6. 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: B

Clarification: The Fourier representation of the output voltage is given by

Put 2d = π & n = 1.

7. In case of a single-pulse width modulation with the pulse width = 2d, the peak value of the fundamental component of voltage is given by the expression

A. 4Vs/π B. Vs C. (4Vs/π) sin 2d D. (4Vs/π) sin d Answer: D

Clarification: For the fundamental component put n = 1.

Vo = (4Vs/π) sin (D. sin (ωt)

Hence the peak value is (4Vs/π) sin d.

8. 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: C

Clarification: To eliminate, the nth harmonic, nd is made equal to π radians, or d = π/n.

From the below expression,

when nd = π. sin nd = 0 hence, that output voltage harmonic is eliminated.

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## [Solved] In a single

Single-pulse modulation: It consists of a pulse width of 2d located symmetrically about π/2 and another pulse located at symmetrically about 3π/2. The

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## Question

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## In a single-phase inverter using single pulse modulation for control of output voltage, Harmonics of the order ‘n’ can be eliminated by making the pulse width equal to

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4π/n 2π/n π/n π/2n

## Answer (Detailed Solution Below)

Option 2 : 2π/n

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## Detailed Solution

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Single-pulse modulation:

It consists of a pulse width of 2d located symmetrically about π/2 and another pulse located at symmetrically about 3π/2. The range of pulse width varies from 0 to π.

The output voltage is controlled by varying pulse width.

**To eliminate nth harmonic, ‘nd’ should be made equal to π**.

This method of voltage control, a great deal of harmonic content is introduced in the output voltage, particularly at low output voltage levels.

The output voltage waveform of a single-phase full-bridge inverter is represented as below.

v0=∑n=1,3,5∞4Vsnπsinnπ2sinndsinnωt

v0=4Vsπ[sindsinωt−13sin3dsin3ωt+15sin5dsin5ωt]

If nd is equal to π ord=πn

or if pulse width is made equal to

2d=2πn

**, it shows that nth harmonic is eliminated from the inverter output voltage.**

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**Q1.**A 3-phase grid-connected voltage source converter with DC link voltage of 1000 V is switched using sinusoidal Pulse Width Modulation (PWM) technique. If the grid phase current is 10 A and the 3-phase complex power supplied by the converter is given by (−4000 − j3000) VA, then the modulation index used in sinusoidal PWM is ___________. (round off to two decimal places)

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**Q7.**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 pulses per half cycle is

**Q8.**In single pulse modulation PWM inverter third harmonics can be eliminate if the pulse – width is made equal to

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**Q3.**A 3-phase grid-connected voltage source converter with DC link voltage of 1000 V is switched using sinusoidal Pulse Width Modulation (PWM) technique. If the grid phase current is 10 A and the 3-phase complex power supplied by the converter is given by (−4000 − j3000) VA, then the modulation index used in sinusoidal PWM is ___________. (round off to two decimal places)

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## PWM Inverters

This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “PWM Inverters-1”. 1. In the single-pulse width modulation method, the output voltage waveform is symmetrical about __________ a) π b) 2π c) π/2 d) π/4 2. In the single-pulse width modulation method, the output voltage waveform is symmetrical about ____________ in the ... Read more

## Power Electronics Questions and Answers – PWM Inverters-1

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This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “PWM Inverters-1”.

1. In the single-pulse width modulation method, the output voltage waveform is symmetrical about __________

a) π b) 2π c) π/2 d) π/4 View Answer

2. In the single-pulse width modulation method, the output voltage waveform is symmetrical about ____________ in the negative half cycle.

a) 2π b) 3π/2 c) π/2 d) 3π/4 View Answer

3. The shape of the output voltage waveform in a single PWM is

a) square wave b) triangular wave

c) quasi-square wave

d) sine wave View Answer

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4. 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(nd)].

d) (2Vs/nπ) [sin(nπ/2) sin(nd)].

View Answer

5. 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(nd)].

d) (2Vs/nπ) [sin(nπ/2) sin(nd)].

View Answer

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6. 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 View Answer

7. In case of a single-pulse width modulation with the pulse width = 2d, the peak value of the fundamental component of voltage is given by the expression

a) 4Vs/π b) Vs c) (4Vs/π) sin 2d d) (4Vs/π) sin d View Answer advertisement

8. 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 View Answer

9. 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 View Answer advertisement

10. 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° View Answer

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Guys, does anyone know the answer?