21. Calculate the maximum frequency for ASCI using the data: R=15 kΩ, C=5 μF.
A. 3.51 Hz
B. 3.69 Hz
C. 3.33 Hz
D. 3.98 Hz
Answer: C
The maximum frequency for ASCI is
1÷(4×R×C) = 1÷(4×15×5×.001) = 3.33 Hz.
The total frequency is the sum of charging and discharging frequency.
22. The output current waveform for R load in CSI is ___________
A. Square
B. Triangular
C. Constant
D. Vertical
Answer: A
The output current of CSI for R load is square in nature. The amplitude of the output current varies from I to -I.
23. T.H.D value for CSI is ________________
A. 48.43 %
B. 41.15 %
C. 39.15 %
D. 46.48 %
Answer: A
T.H.D value for VSI is 48.43 %. Triple harmonics are present in CSI due to which harmonic content increases.
24. What is the distortion factor value in CSI?
A. .85
B. .90
C. .95
D. .88
Answer: B
The distortion value in CSI is .90. The r.m.s value of the fundamental current is 2√2I÷π and the r.m.s value of the output current is I. The distortion factor is (2√2I÷π)÷I = .90.
25. Number of switches turned on in CSI at a single time is __________
A. 2
B. 4
C. 5
D. 3
Answer: A
In CSI two switches conduct at a single time. The common switch used in CSI is a thyristor. Thyristors are unidirectional, and bipolar in nature.
26. Calculate the r.m.s value of the output current having an amplitude of 2 A for CSI.
A. 3 A
B. 4 A
C. 2 A
D. 1 A
Answer: B
The r.m.s value of the output current having an amplitude of 2 A for CSI is 2A. The waveform for output current is a square wave. The r.m.s value of the square wave is its amplitude.
27. Calculate the r.m.s value of the fundamental component of the output current having an amplitude of 3 A for CSI.
A. 2.80 A
B. 2.70 A
C. 2.54 A
D. 3.48 A
Answer: B
The r.m.s value of the fundamental component of the output current is
2√2I÷π=8.48÷3.14=2.70 A. The r.m.s value of the output current is I.
28. Calculate the string efficiency if the de-rating factor is .76.
A. 24 %
B. 25 %
C. 26 %
D. 27 %
Answer: A
The string efficiency is calculated for the series and parallel connection of SCRs. The value of string efficiency is 1-(De-rating factor)=1-.76=24 %.
29. 20 V rated 8 SCRs are connected in series. The operation voltage of the string is 50. Calculate the De-rating factor.
A. .67
B. .68
C. .69
D. .70
Answer: B
The string efficiency can be calculated using the formula
operation voltage÷(Number of SCRs×Rated voltage)=
50÷(20×8)=.31.
The De-rating factor value is 1-.31=.68.
30. Forced commutated CSI require _________
A. Diode
B. Resistor
C. Inductor
D. Capacitor
Answer: D
Forced commutated CSI requires a capacitor. The capacitor acts as a commutating element. It is connected in parallel with the load.
