Power Electronics Questions and Answers – Applications of Power Electronics-2

This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “Applications of Power Electronics-2”.

1. HVDC transmission lines are __________ as compared to HVAC lines.
a) difficult to erect
b) more expensive for long distances
c) more expensive for short distances
d) less expensive for short distances
View Answer

Answer: c
Explanation: HVDC lines require additional cost of the converting and inverting equipments, hence they are more expensive for short distances as compared to HVAC lines.

2. In HVDC transmission lines
a) both the stations operate as an inverter
b) both the stations operate as a converter
c) one acts as a converter and other as an inverter
d) depends upon the type of the load
View Answer

Answer: c
Explanation: The supply side station is the converting station, power is transmitted in dc then again converted back to ac at the inverting or receiving station further which it is distributed in ac to houses.

3. Two six pulse converters used for bipolar HVDC transmission system, are rated at 1000 MW, +- 200 kV. What is the dc transmission voltage?
a) 200 kV
b) 400 kV
c) 500 kV
d) 100 kV
View Answer

Answer: b
Explanation: As the link is bipolar, the total voltage transmitted will 200 + 200 kV.
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4. Two six pulse converters used for bipolar HVDC transmission system, are rated at 1000 MW, +- 200 kV. Find the dc current in the transmission line.
a) 500 A
b) 25 A
c) 2500 A
d) 5 A
View Answer

Answer: c
Explanation: Transmission voltage = 200 + 200 = 400 kV.
I = P/V = 1000 mW/ 400 kV = 2500 A.

5. Two six pulse converters used for bipolar HVDC transmission system, are rated at 1000 MW, +- 200 kV. Find the rms current rating required for the SCRs.
a) 2500 A
b) 1350 A
c) 1445 A
d) none of the mentioned
View Answer

Answer: c
Explanation: Transmission voltage = 200 + 200 = 400 kV.
I = P/V = 1000 mW/ 400 kV = 2500 A.
As in 3-phase full converter each SCR conducts for 120° for a total period of 360°.
Irms = 2500 x √(120/360) = 1443.4 A. Nearly about 1445 A as it is a standard current rating.
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6. For high power applications _________ are used as static switches whereas for low power applications __________ are used.
a) Transistors, SCRs
b) SCRs, transistors
c) Diodes, transistors
d) SCRs, diodes
View Answer

Answer: b
Explanation: As SCR are of higher rating they are preferred in high power applications.

7. _________ can be used as a single phase static ac switch.
a) Diode
b) SCR
c) DIAC
d) TRAIC
View Answer

Answer: d
Explanation: SCR cannot be used, as it is unidirectional. Diode isn’t a switch nor is the DIAC.
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8. ___________ can be used as a dc static switch.
a) GTO
b) Transistor
c) Both GTO and transistor
d) TRIAC
View Answer

Answer: c
Explanation: Both GTO and transistor can be used as a dc static switch.

9. A single-phase ac switch is used in between a 230 V source and load of 2 kW and 0.8 lagging power factor. Determine the rms current rating required by the SCR. Use the factor of safety = 2.
a) 10.87 A
b) 87 A
c) 21.74 A
d) 32 A
View Answer

Answer: c
Explanation: I = (200√2)/(230 x 0.8) = 15.37 A.
I(rms) = 15.37/1.414 = 10.87
Required rating = 10.87 x factor of safety = 15.37 x 2 = 21.74 A.
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10. Solid State Relays (SSRs) have
a) moving parts
b) no moving parts
c) a coil
d) a contactor
View Answer

Answer: b
Explanation: SSRs have no moving parts, they simply consist of a LED and a transistor or photo diode.

Sanfoundry Global Education & Learning Series – Power Electronics.

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

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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