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.