Power Electronics Questions and Answers – Single Phase VSI-3

This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “Single Phase VSI-3”.

1. The output voltage from a single phase full wave bridge inverter varies from
a) Vs to –Vs
b) Vs to zero
c) Vs/2 to zero
d) –Vs/2 to Vs/2
View Answer

Answer: a
Explanation: The output from a full wave bridge inverter varies from Vs to –Vs.

2. 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
View Answer

Answer: c
Explanation: When two SCRs are conducting, T1-T2 or T3-T4, the output voltage magnitude is Vs. When the diodes are conducting, freewheeling action is taking place and voltage is zero.

3. In the following circuit, the diodes D1 to D4 are used to
The diodes D1 to D4 are used to send current back to the dc source when SCRs are off
a) reduce the switching losses
b) send current back to the dc source when SCRs are off
c) send current back to the load when SCRs are off
d) send current back to the dc source when SCRs are conducting
View Answer

Answer: b
Explanation: Diodes are connected in anti-parallel with the SCRs during inductive loads for freewheeling actions.
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4. For a full wave bridge inverter, the output voltage (Vo)
a) Vo = Vs/2 for 0 < t < T/2
b) Vo = Vs for 0 < t <T/2
c) Vo = Vs for T/2< t < T
d) Vo = -Vs for T/2< t < 3T/2
View Answer

Answer: b
Explanation: For the first half cycle, Vo = Vs and for the second half cycle Vo = -Vs.

5. For a half wave bridge inverter, the output voltage
a) Vo = – Vs/2 for 0 < t < T/2
b) Vo = – Vs/2 for T/2< t<T
c) Vo = – Vs for 0 < t < T/2
d) Vo = Vs/2 for T/2< t < T
View Answer

Answer: b
Explanation: In case of a half wave inverter, for the first half cycle, Vo = Vs/2 and for the second half cycle Vo = -Vs/2.
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6. The fundamental component of output voltage for a half wave bridge inverter is given by
a) (4Vs/π) sinωt
b) (2Vs/π) sinωt
c) (Vs/2π) sinωt
d) (Vs)
View Answer

Answer: b
Explanation: The fourier analysis of half wave inverter gives,
The fourier analysis of half wave inverter gives
Put n = 1 for the fundamental component.

7. 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)
View Answer

Answer: b
Explanation: The fourier analysis of full wave inverter gives,
Vo =
The component of output voltage for full wave bridge inverter is given by (4Vs/π) sinωt
Put n = 1 for the fundamental component.

8. 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
View Answer

Answer: b
Explanation: The fundamental component of voltage = (2Vs/π) sinωt.
Peak value Vm = 2Vs/π
Rms value = 2Vs/π√2 = 103.552 V.

9. 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
View Answer

Answer: b
Explanation: Peak value Vm = 2Vs/π
Rms value = 2Vs/π√2 = 103.552 V
Io = Vo/R = 103.552/2 = 51.776 A.
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10. 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
View Answer

Answer: c
Explanation: Peak value Vm = 2Vs/π
Rms value = 2Vs/π√2 = 103.552 V
Io = Vo/R = 103.552/2 = 51.776 A
P = Io2 x R = 5361.5 Watts.

Sanfoundry Global Education & Learning Series – Power Electronics.

To practice all areas of Power Electronics, here is complete set of 1000+ Multiple Choice Questions and Answers.

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