Electric Drives Questions and Answers – Solid-State Switching Circuits – Single Phase, Full-Wave, AC/DC Conversion for Resistive Loads

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This set of Electric Drives Questions and Answers for Aptitude test focuses on “State Switching Circuits – Single Phase, Full-Wave, AC/DC Conversion for Resistive Loads “.

1. Calculate the value of the Input power factor for 1-Φ Full wave bridge rectifier if the firing angle value is 39°.
a) .69
b) .59
c) .78
d) .15
View Answer

Answer: a
Explanation: The value of the input power factor for 1-Φ Full wave bridge rectifier is .9cos(67°)=.69. The input power factor is a product of distortion factor and displacement factor.
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2. Calculate the value of the fundamental displacement factor for 1-Φ Full wave bridge rectifier if the firing angle value is 38°.
a) .22
b) .78
c) .33
d) .44
View Answer

Answer: b
Explanation: Fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current. D.F=cos(∝)=cos(38°)=0.78.

3. Calculate the value of the fundamental displacement factor for 1-Φ Full wave semi-converter if the firing angle value is 69°.
a) .48
b) .24
c) .82
d) .88
View Answer

Answer: c
Explanation: Fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current. The fundamental displacement factor for 1-Φ Full wave semi-converter is cos(∝÷2)=cos(34.5°)=.82.

4. 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
View Answer

Answer: a
Explanation: The fundamental component of source current in 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.

5. 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
View Answer

Answer: d
Explanation: The circuit turn-off time for 1-Φ Full wave bridge rectifier is (π-α)÷ω. The value of circuit turn-off time is (π-145°)÷5=87.2 msec.
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6. Calculate the fundamental component of source current in 1-Φ Full wave bridge rectifier for the load(Highly inductive) current=78 A.
a) 78 A
b) 45 A
c) 69 A
d) 13 A
View Answer

Answer: a
Explanation: The fundamental component of source current in 1-Φ Full wave bridge rectifier is Io. It is the r.m.s value of the source current. Is(r.m.s)=Io=78 A.

7. Calculate the r.m.s value of source current in 1-Φ Full wave semi-converter for the load (Highly inductive) current=51.2 A and α=15°.
a) 10.53 A
b) 14.52 A
c) 44.92 A
d) 49.02 A
View Answer

Answer: d
Explanation: The r.m.s value of source current in 1-Φ Full wave semi-converter is Io√π-α÷π. It is the r.m.s value of the source current. I(r.m.s) = Io√π-α÷π = 51.2(√.916) = 49.02 A.

8. Calculate the r.m.s value of thyristor current in 1-Φ Full wave semi-converter for the load (Highly inductive) current=2.2 A and α=155°. (Asymmetrical configuration)
a) .58 A
b) .57 A
c) .51 A
d) .52 A
View Answer

Answer: b
Explanation: The r.m.s value of source current in 1-Φ Full wave semi-converter is Io√π-α÷2π. It is the r.m.s value of the thyristor current. I(r.m.s) = Io√π-α÷2π=2.2(√.069)=.57 A.

9. Calculate the r.m.s value of diode current in 1-Φ Full wave semi-converter for the load (Highly inductive) current=5.1 A and α=115°. (Asymmetrical configuration)
a) 4.21 A
b) 4.61 A
c) 4.71 A
d) 4.52 A
View Answer

Answer: b
Explanation: The r.m.s value of diode current in 1-Φ Full wave semi-converter is Io√π+α÷2π. It is the r.m.s value of the diode current. I(r.m.s) = Io√π+α÷π=5.1(√.819)=4.61 A.
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10. Calculate the average value of thyristor current in 1-Φ Full wave semi-converter for the load (Highly inductive) current=25.65 A and α=18°. (Asymmetrical configuration)
a) 11.54 A
b) 12.15 A
c) 15.48 A
d) 14.52 A
View Answer

Answer: a
Explanation: The average value of thyristor current in 1-Φ Full wave semi-converter is Io(π-α÷2π). It is the average value of the thyristor current. Iavg = Io(π-α÷2π)=25.65(.45)=11.54 A.

11. Calculate the average value of diode current in 1-Φ Full wave semi-converter for the load (Highly inductive) current=75.2 A and α=41°. (Asymmetrical configuration)
a) 46.16 A
b) 42.15 A
c) 41.78 A
d) 41.18 A
View Answer

Answer: a
Explanation: The average value of diode current in 1-Φ Full wave semi-converter is Io(π+α÷2π). It is the average value of the diode current. Iavg = Io(π+α÷2π)=75.2(.61)=46.16 A.

12. Calculate the average value of diode current in 1-Φ Full wave semi-converter for the load (Highly inductive) current=5.2 A and α=11°. (F.D configuration)
a) .32 A
b) .31 A
c) .25 A
d) .27 A
View Answer

Answer: b
Explanation: The average value of diode current in 1-Φ Full wave semi-converter is Io(α÷π). It is the average value of the diode current. Iavg= Io(α÷π)=5.2(.061)=.31 A.

13. Calculate the r.m.s value of diode current in 1-Φ Full wave semi-converter for the load (Highly inductive) current=.2 A and α=74°. (F.D configuration)
a) .154 A
b) .248 A
c) .128 A
d) .587 A
View Answer

Answer: c
Explanation: The r.m.s value of diode current in 1-Φ Full wave semi-converter is Io√(α÷π). It is the r.m.s value of the diode current. Ir.m.s = Io√(α÷π)=.2√(.41)=.128 A.
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14. Diodes in 1-Φ Full wave semi-converter protects the thyristor from short-circuiting.
a) True
b) False
View Answer

Answer: a
Explanation: Diodes in 1-Φ Full wave semi-converter protects the thyristor from short-circuiting. They provide the gap from (α, π+α) to avoid the conduction of one leg thyristors.

15. The problem of short-circuiting in 1-Φ Full wave semi-converter is very common.
a) True
b) False
View Answer

Answer: a
Explanation: The problem of short-circuiting in 1-Φ Full wave semi-converter is very common. Diodes protect the thyristor from short-circuiting. They provide the gap from (α, π+α) to avoid the conduction of one leg thyristors.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn