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
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
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
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
Explanation: Diodes are connected in anti-parallel with the SCRs during inductive loads for freewheeling actions.
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
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
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.
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
Explanation: 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
Explanation: The fourier analysis of full wave inverter gives,
Vo =
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
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
Explanation: Peak value Vm = 2Vs/π
Rms value = 2Vs/π√2 = 103.552 V
Io = Vo/R = 103.552/2 = 51.776 A.
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
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.
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