DC to DC Conversion MCQ [Free PDF] – Objective Question Answer for DC to DC Conversion Quiz

21. Full form of CSI is ___________

A. Counter source inverter
B. Counter severe inverter
C. Current source inverter
D. Current severe inverter

Answer: C

CSI stands for Current source inverter. The output voltage of CSI is variable but the output current is fixed.   

 

22. Number of switches turned on in 3-phase 180° VSI at a single time are __________

A. 3
B. 2
C. 1
D. 4

Answer: B

In 3-phase 180° VSI each phase conducts for 180° and only two switches from different phases conduct at a single time.   

 

23. Number of switches turned on in 3-phase 120° VSI at a single time are __________

A. 2
B. 4
C. 5
D. 3

Answer: D

In 3-phase 120° VSI each phase conducts for 120° and only three switches from different phases conduct at a single time.   

 

24. Calculate the phase voltage for 3-∅ 180° VSI if the value of the DC supply is 20 V.

A. 9.40 V
B. 9.42 V
C. 9.18 V
D. 9.78 V

Answer: B

The phase voltage for 3-∅ 180° VSI is

(√2÷3)×VDC=.471×20=9.42 V.

In 3-phase 180° VSI each phase conducts for 180° and only two switches from different phases conduct at a single time.   

 

25. Calculate the line voltage for 3-∅ 180° VSI if the value of the DC supply is 22 V.

A. 18.52 V
B. 18.12 V
C. 17.96 V
D. 15.48 V

Answer: C

The line voltage for 3-∅ 180° VSI is

(√2÷√3)×VDC

=.81×22=17.96 V.

In 3-phase 180° VSI each phase conducts for 180° and only two switches from different phases conduct at a single time.   

 

26. Calculate the line voltage for 3-∅ 120° VSI if the value of the DC supply is 24 V.

A. 16.52 V
B. 16.97 V
C. 12.96 V
D. 12.48 V

Answer: B

The line voltage for 3-∅ 120° VSI is

(VDC÷√2)

=.707×24=16.97 V.

In 3-phase 120° VSI each phase conducts for 120° and only three switches from different phases conduct at a single time.   

 

27. Calculate the phase voltage for 3-∅ 120° VSI if the value of DC supply is 26 V.

A. 10.52 V
B. 10.97 V
C. 10.96 V
D. 10.61 V

Answer: D

The line voltage for 3-∅ 120° VSI is (VDC÷√6)=10.61 V.

In 3-phase 120° VSI each phase conducts for 120° and only three switches from different phases conduct at a single time.   

 

28. Calculate power absorbed by 5 Ω load in 3-∅ 120° VSI if the value of DC supply is 16 V.

A. 17.06 W
B. 15.15 W
C. 18.25 W
D. 19.26 W

Answer: A

The power absorbed by 5 Ω load in 3-∅ 120° VSI if the value of DC supply is 16 V is

Vph2÷R=(16÷√3)2÷5=17.06 W.   

 

29. Calculate power absorbed by 10 Ω load in 3-∅ 180° VSI if the value of DC supply is 36 V.

A. 20.6 W
B. 24.5 W
C. 26.4 W
D. 28.8 W

Answer: D

The power absorbed by 10 Ω load in 3-∅ 180° VSI if the value of DC supply is 36 V is

Vph2÷R=(22.6÷3)2÷10=28.8 W.   

 

30. T.H.D value for 3-∅ 180° VSI is ________________

A. 36 %
B. 31 %
C. 39 %
D. 46 %

Answer: B

T.H.D value for 3-∅ 180° VSI is 31 %. Triple harmonics are absent in 3-∅ 180° VSI and 3-∅ 120° VSI. Only 6k±1 harmonics are present.   

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