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

«
»

This set of Electric Drives Multiple Choice Questions & Answers (MCQs) focuses on “Solid-State Switching Circuits – Three Phase, Half-Wave, AC/DC Conversion for Resistive Loads”.

1. Calculate the Vo(avg) for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 440 V.
a) 297.25 V
b) 298.15 V
c) 298.11 V
d) 300.15 V
View Answer

Answer: a
Explanation: The Vo(avg) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2π. The value of output voltage is 3Vml÷2π=3×√2×440÷6.28=297.25 V.
advertisement

2. Calculate the pulse number if the supply frequency is 2π and the output frequency is 2π÷3.
a) 4
b) 5
c) 6
d) 3
View Answer

Answer: d
Explanation: The pulse number can be calculated using the ratio of input frequency to the output frequency. The value of pulse number (P) is 2π÷(2π÷3)=3. It is a three-pulse converter or 3-Φ phase Half-wave uncontrolled rectifier.

3. Calculate the average value of current for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 400 V and resistive load value is 5 Ω.
a) 54.04 A
b) 57.26 A
c) 51.64 A
d) 58.15 A
View Answer

Answer: a
Explanation: The Io(avg) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2πR. The value of output voltage is 3Vml÷2πR=3×√2×440÷6.28×5=54.04 A.

4. In 3-Φ Fully controlled rectifier calculate the average value of the voltage if the supply is 400 V and firing angle is 45°.
a) 381.15 V
b) 382.16 V
c) 383.19 V
d) 384.25 V
View Answer

Answer: b
Explanation: In 3-Φ Fully controlled rectifier, the average value of the voltage is 3Vml(cos(∝))÷π=3×400×√2(cos(45°))÷3.14=382.16 V.

5. Calculate the Vo(r.m.s) (Highly inductive load) for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 441 V.
a) 297.25 V
b) 298.15 V
c) 298.11 V
d) 300.15 V
View Answer

Answer: a
Explanation: The Vo(r.m.s) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2π. The value of output voltage is 3Vml÷2π=3×√2×441÷6.28=297.25 V.
advertisement

6. Calculate the Vo(avg) for the 3-Φ phase Half-wave controlled rectifier if the supply value is 364 V and the value of firing angle is 2°.
a) 247.62 V
b) 245.76 V
c) 214.26 V
d) 233.26 V
View Answer

Answer: b
Explanation: The Vo(avg) for the 3-Φ phase Half-wave controlled rectifier is 3Vmlcos(α)÷2π. The value of output voltage is 3Vmlcos(α)÷2π=3×√2×364×(.99)÷6.28=245.76 V.

7. Calculate the value of the Input power factor for 3-Φ Fully controlled rectifier if the firing angle value is 16°.
a) .96
b) .91
c) .93
d) .94
View Answer

Answer: b
Explanation: The value of the input power factor for 3-Φ Fully controlled rectifier is .95cos(16°)=.91. The input power factor is a product of distortion factor and displacement factor.

8. In 3-Φ Semi-controlled rectifier calculate the average value of the voltage if the supply is 299 V and firing angle is 56.15°.
a) 311.26 V
b) 304.26 V
c) 314.51 V
d) 312.45 V
View Answer

Answer: c
Explanation: In 3-Φ Semi-controlled rectifier, the average value of the voltage is 3Vml(1+cos(∝))÷2π=3×299×√2(1+cos(56.15°))÷6.28=314.51 V.

9. Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 13° and supply frequency is 49.5 Hz.
a) 730.2 msec
b) 740.8 msec
c) 754.5 msec
d) 755.1 msec
View Answer

Answer: a
Explanation: The circuit turn-off time for 3-Φ Fully controlled rectifier is (240°-α)÷ω. The value of circuit turn-off time for ∝ < 60° is (240°-13°)÷6.28×49.5=730.2 msec.
advertisement

10. Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 170° and supply frequency is 50.5 Hz.
a) 32.4 msec
b) 35.2 msec
c) 39.3 msec
d) 31.5 msec
View Answer

Answer: d
Explanation: The circuit turn-off time for 3-Φ Fully controlled rectifier is (180°-α)÷Ω. The value of circuit turn-off time for ∝ ≥ 60° is (180°-170°)÷6.28×50.5=31.5 msec.

11. Calculate the form factor if V(r.m.s)=45 V, V(avg)=15 V.
a) 2
b) 5
c) 3
d) 8
View Answer

Answer: c
Explanation: The form factor is defined as the ratio of the Vr.m.s÷Vavg=45÷15=3. The r.m.s value is three times of average value Vavg.

12. Calculate the Vo(avg) for the 3-Φ phase Half-wave controlled rectifier if the supply value is 480 V and the value of firing angle is 92°.
a) 264.02 V
b) 487.26 V
c) 858.26 V
d) 248.25 V
View Answer

Answer: a
Explanation: The Vo(r.m.s) for the 3-Φ phase Half-wave controlled rectifier is 3Vm(1+cos(α))÷2π. The value of output voltage is 3Vm(1+cos(α+30))÷2π=3×480×√3×√2(1+cos(92))÷2π=264.02 V.

13. Full form of SCR is ____________
a) Silicon controlled rectifier
b) State-controlled rectifier
c) State cover rectifier
d) State-controlled reset
View Answer

Answer: a
Explanation: SCR stands for silicon controlled rectifier. It is a semi-controlled, bipolar, uni-directional switch. It is a high power rating than other power electronic devices.
advertisement

14. Full form of TRIAC is __________
a) Triode for Alternating current
b) Tri for Alternating current
c) Triode for Alternating counter
d) Tri for Alternating counters
View Answer

Answer: a
Explanation: TRIAC stands for Triode for Alternating current. It is a bipolar, bidirectional switch. It is used in fan regulators to control the speed of fans.

15. TRIAC is a unipolar switch.
a) True
b) False
View Answer

Answer: b
Explanation: TRIAC stands for Triode for Alternating current. It is a bipolar, bidirectional switch. It is used in fan regulators to control the speed of fans.

Sanfoundry Global Education & Learning Series – Electric Drives.

To practice all areas of Electric Drives, here is complete set of 1000+ Multiple Choice Questions and Answers.

Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

advertisement
advertisement
advertisement
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