11. Calculate the r.m.s value of the current through the thyristor in the case of a 1-Φ Full wave bridge rectifier if the value of the load current is 2 A.
A. 1.414 A
B. 1.214 A
C. 1.347 A
D. 1.657 A
Answer: A
The r.m.s value of the current through the thyristor in the case of 1-∅ a full-wave bridge rectifier is
Io÷√2=√2 A=1.414 A.
Each thyristor conducts for 180°.
12. Calculate the value of THD value for a 1-Φ Full wave bridge rectifier.
A. 48.43 %
B. 47.25 %
C. 49.26 %
D. 50.48 %
Answer: A
The value of the distortion factor is .9. The value of THD value for the 1-Φ Full wave bridge rectifier is
√(1÷.9)2-1=48.43 %.
THD measures the amount of harmonic distortion.
13. Calculate the value of the Input power factor for a 1-Φ Full wave bridge rectifier if the firing angle value is 45°.
A. .65
B. .64
C. .61
D. .63
Answer: D
The value of the input power factor for the 1-Φ Full wave bridge rectifier is .9cos(45°)=.63.
The input power factor is a product of the distortion factor and displacement factor.
14. Calculate the value of the fundamental displacement factor for a 1-Φ Full wave bridge rectifier if the firing angle value is 60°.
A. .5
B. .4
C. .2
D. .8
Answer: A
The fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current.
D.F=cos(∝)=cos(60°)=0.5.
15. Calculate the value of the fundamental displacement factor for a 1-Φ Full-wave semi-converter if the firing angle value is 20°.
A. .82
B. .98
C. .74
D. .26
Answer: B
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(10°)=.98.
16. Calculate the output frequency for the two-pulse converter if the supply frequency is 20 Hz.
A. 40 Hz
B. 20 Hz
C. 60 Hz
D. 90 Hz
Answer: A
The output of a two-pulse converter consists of two pulses in one cycle. The output frequency of the two pulse converters is
2×supply frequency=2×20=40 Hz.
17. Calculate the pulse number if the supply frequency is 2π and the output frequency is π÷3.
A. 4
B. 2
C. 6
D. 8
Answer: C
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÷3=6. It is a six-pulse converter.
18. In a 3-Φ Fully controlled rectifier calculate the average value of the voltage if the supply is 400 V and the firing angle is 15°.
A. 521.2 V
B. 522 V
C. 523 V
D. 524 V
Answer: B
In 3-Φ Fully controlled rectifier, the average value of the voltage is
3Vml(cos(∝))÷π
=3×400×√2(cos(15°))÷3.14=522 V.
19. Calculate the value of the Input power factor for a 3-Φ Fully controlled rectifier if the firing angle value is 70°.
A. .32
B. .38
C. .31
D. .33
Answer: A
The value of the input power factor for a 3-Φ Fully controlled rectifier is
.95cos(70°)=.32.
The input power factor is a product of the distortion factor and displacement factor.
20. Calculate the value of THD value for a 3-Φ Fully controlled rectifier.
A. 48.43 %
B. 47.25 %
C. 39.26 %
D. 31 %
Answer: D
The value of the distortion factor is .95. The value of THD value for a 3-Φ Fully controlled rectifier is
√(1÷.95)2-1=31 %.