11. Calculate the circuit turn-off time for Half-wave controlled rectifier for a ω=5 rad/sec for resistive load.
A. .62 sec
B. .42 sec
C. .58 sec
D. .64 sec
Answer: A
The value of the circuit turn-off for the Half-wave controlled rectifier for a ω=5 rad/sec for the resistive load is a
π÷Ω=π÷5=.62 sec.
12. Calculate the string efficiency if the de-rating factor is .429.
A. 48.1 %
B. 57.1 %
C. 47.8 %
D. 46.5 %
Answer: B
The string efficiency is calculated for the series and parallel connection of SCRs.
The value of string efficiency is 1-(De-rating factor)=1-.429=57.1 %.
13. Calculate the output frequency for the six-pulse converter if the supply frequency is 10 Hz.
A. 40 Hz
B. 30 Hz
C. 60 Hz
D. 80 Hz
Answer: C
The output of a six-pulse converter consists of six pulses in one cycle. The output frequency of the six pulse converter is 6×supply frequency=6×10=60 Hz.
14. Calculate the pulse number if the supply frequency is 2π and the output frequency is π÷6.
A. 4
B. 12
C. 16
D. 8
Answer: B
The pulse number can be calculated using the ratio of input frequency to the output frequency. The value of pulse number (P) is 2π÷π÷6=12. It is a twelve-pulse converter.
15. Volt-sec balance method is based on the principle of the energy of conservation.
A. True
B. False
Answer: A
The volt-sec balance method states that the net area over the cycle will be zero. It is based on the principle of the energy of conservation. The amount of charging is equal to discharging.
16. Calculate the value of the Input power factor for a 1-Φ Full wave bridge rectifier if the firing angle value is 39°.
A. .69
B. .59
C. .78
D. .15
Answer: A
The value of the input power factor for the 1-Φ Full wave bridge rectifier is
.9cos(67°)=.69.
The input power factor is a product of the distortion factor and displacement factor.
17. Calculate the value of the fundamental displacement factor for a 1-Φ Full wave bridge rectifier if the firing angle value is 38°.
A. .22
B. .78
C. .33
D. .44
Answer: B
The fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current.
D.F=cos(∝)=cos(38°)=0.78.
18. Calculate the value of the fundamental displacement factor for a 1-Φ Full-wave semi-converter if the firing angle value is 69°.
A. .48
B. .24
C. .82
D. .88
Answer: C
The fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current. The fundamental displacement factor for a 1-Φ.
Full-wave semi-converter is cos(∝÷2)=cos(34.5°)=.82.
19. Calculate the fundamental component of source current in 1-Φ Full wave bridge rectifier for load(Highly inductive) current=3.14 A.
A. 2.82 A
B. 1.45 A
C. 3.69 A
D. 4.78 A
Answer: A
The fundamental component of source current in a 1-Φ Full wave bridge rectifier is
2√2Io÷π.
It is the r.m.s value of the fundamental component.
Is1(r.m.s) = 2√2Io÷π
=2√2=2.82 A.
20. Calculate the circuit turn-off time for 1-Φ Full wave bridge rectifier for α=145°. Assume the value of ω=5 rad/sec.
A. 84.9 msec
B. 94.5 msec
C. 101.2 msec
D. 87.2 msec
Answer: D
The circuit turn-off time for the 1-Φ Full wave bridge rectifier is (π-α)÷ω. The value of circuit turn-off time is
