Power Electronics Questions and Answers – 3-Phase Bridge Inverters-1

This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “3-Phase Bridge Inverters-1”.

1. Identify the below given circuit.
Three-phase bridge thyristor inverter used as the switching device
a) Three-phase bridge regulator
b) Three-phase bridge type semi-converter circuit
c) Three-phase bridge thyristor inverter
d) Three-phase bridge IGBT inverter
View Answer

Answer: c
Explanation: It is a three-phase bridge type inverter. As SCRs are used as the switching device, it is called as a thyristor inverter.

2. A three-phase bridge inverter requires minimum of _____________ switching devices.
a) 3
b) 4
c) 6
d) 8
View Answer

Answer: c
Explanation: It requires a min. 6 devices, 2 in each leg. Switching devices could be anything BJT, MOSFET or an IGBT. SCRs are used when very high power ratings are required.

3. The below given inverter circuit is a __ step inverter.
Three-phase bridge thyristor inverter used as the switching device
a) 3
b) 2
c) 6
d) none of the mentioned
View Answer

Answer: c
Explanation: The three-phase bridge type is a 6-step inverter. That means, the firing changes from one SCR to another 6 times per cycle.
advertisement
advertisement

4. In the three-phase bridge inverter, each step consists of
a) 30°
b) 60°
c) 90°
d) will depend on the value of the firing angle
View Answer

Answer: b
Explanation: It is a 6 step inverter. Hence, 360/6 = 60°. This means that the SCRs are gated every 60° in proper sequence.

5. In inverters, to make the supply voltage constant
a) an inductor is placed in series with the load
b) capacitor is connected in parallel to the load side
c) capacitor is connected in parallel to the supply side
d) none of the mentioned
View Answer

Answer: c
Explanation: A large C connected across the input terminal keep the supply voltage from altering.
Note: Join free Sanfoundry classes at Telegram or Youtube

6. In the 180° mode VSI, ___________ devices conduct at a time.
a) 5
b) 2
c) 3
d) 4
View Answer

Answer: c
Explanation: Three devices conduct at a time. One from the upper pair and two from the lower pair or vice-versa.

7. In the figure given below, for 180° mode of operation if T1 is fired at 0°. Then SCRs T3 and T5 should be fired at _________ and _________ respectively.
Three-phase bridge thyristor inverter used as the switching device
a) 180°, 360°
b) 90°, 180°
c) 120°, 240°
d) none of the mentioned
View Answer

Answer: c
Explanation: T1-T4 form the first pair. T3-T6 form the second pair, and like-wise. For the 180° mode, each SCR conducts for 180°, but the groups of SCRs lag the prior group by an angle of 120°. e.g. If T1 is fired at 0 then T3 must be fired at an angle of 0 + 120° and T5 at 120 + 120 = 240°.
advertisement

8. For a three phase bridge inverter in the 180° mode, ___________ devices are conducting from 120° to 180°.
Three-phase bridge thyristor inverter used as the switching device
a) T1, T6, T5
b) T2, T6, T5
c) T1, T6, T5
d) T1, T2, T3
View Answer

Answer: d
Explanation:

Group I T1 T1 T1 T4 T4 T4 T1 T4
Group II T6 T6 T3 T3 T3 T6 T6 T6
Group III T5 T2 T2 T2 T5 T5 T5 T2
Step No I II III IV V VI I II

Each step consists of 60°. 120° to 180° will be step III.

advertisement

9. _________ SCRs conduct from 300° to 360°.
Three-phase bridge thyristor inverter used as the switching device
a) T1, T2, T3
b) T4, T5, T6
c) T4, T3, T2
d) T1, T6, T5
View Answer

Answer: b
Explanation:

Group I T1 T1 T1 T4 T4 T4 T1 T4
Group II T6 T6 T3 T3 T3 T6 T6 T6
Group III T5 T2 T2 T2 T5 T5 T5 T2
Step No I II III IV V VI I II

Each step consists of 60°. 300° to 360° will be step VI.

10. The diodes D4 and D1 will conduct from
Three-phase bridge thyristor inverter used as the switching device
a) they will never conduct
b) 300° to 360°
c) 120° to 180°
d) insufficient information
View Answer

Answer: d
Explanation: This will depend on the nature on the load, which is not mentioned in the above problem.

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]

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). 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!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
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.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.