# MCQ in Power Electronics Part 6 | ECE Board Exam

(Last Updated On: August 10, 2022) This is the Multiple Choice Questions Part 6 of the Series in Power Electronics as one of the Electronics Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electronics Engineering field, Electronics Books, Journals and other Electronics References.

#### Continue Practice Exam Test Questions Part 6 of the Series

Choose the letter of the best answer in each questions.

251. A 3 phase dual converter consists of

A. two 3 phase semiconverters connected in parallel

B. two 3 phase semiconverters connected in antiparallel

C. two 3 phase full converters connected in antiparallel

D. two 3 phase full converters connected in parallel

Solution:

252. Which inverter circuit uses coupled inductors?

A. Modified McMurray full bridge inverter

B. McMurray Bedford half bridge inverter

C. Modified McMurray Bedford half bridge inverter

D. Both (b) and (c)

Solution:

253. When an SCR is in forward blocking mode, the applied voltage

A. appears across only one junction

B. is equally shared by two junctions

C. is equally shared by three junctions

D. may appear across one or more junctions

Solution:

254. In sinusoidal PWM for inverters the width of different pulses are not the same.

A. True

B. False

C. none

D. all

Solution:

255. The symbol in figure is for

A. UJT

B. PUT

C. SCS

D. SBS

Solution:

256. Mc Murray full bridge inverter uses

A. 4 thyristors and 2 diodes

B. 4 thyristors and 4 diodes

C. 8 thyristors and 4 diodes

D. 8 thyristors and 8 diodes

Solution:

257. In a 3-phase full converter, the instantaneous output voltage can have negative part if

A. firing angle is less than 60°

B. firing angle is less than 90°

C. firing angle is more than 60°

D. firing angle is more than 90°

Solution:

258. The circuit in figure is for

A. resonant commutation

B. line commutation

C. auxiliary commutation

D. complementary commutation

Solution:

259. The main utility of SCR is due to

A. gate triggering

B. high temperature triggering

C. triggering

D. high breakdown voltage

Solution:

260. The symbol in figure is for

A. SUS

B. SBS

C. Shockley diode

D. UJT

Solution:

261. he circuit in figure is for

A. resonant commutation

B. self-commutation

D. auxiliary commutation

Solution:

262. A single phase half bridge inverter required to feed R-L loads needs

A. 2 thyristors

B. 4 thyristors

C. 2 thyristors and two diodes

D. 4 thyristors and 4 diodes

Solution:

263. In a single-phase semi-converter the number of thyristors is

A. 16

B. 8

C. 4

D. 2

Solution:

264. Which of these commutation methods uses two leads?

A. Class A

B. Class B

C. Class C

D. Class D

Solution:

265. The difference between resonant commutation and self-commutation is

A. both these methods are based on entirely different principles

B. in resonant commutation, the commutating elements carry load current but in self commutation, the commutating elements do not carry load current

C. resonant commutation uses L and C but self-commutation uses only capacitor

D. none of the above

Solution:

266. In a series inverter

A. the commutating elements carry full load current

B. the commutating elements carry up to 50% of load current

C. the commutating elements do not carry load current

D. any of the above

Solution:

267. Which of these devices is used in relaxation oscillator?

A. UJT

B. SCR

C. DIAC

D. TRIAC

Solution:

268. Two thyristors of the same rating and specifications

A. will have equal on state voltage drops

B. will have equal forward blocking voltage for the same current

C. will have different on state voltage drops

D. may have equal or different on state voltage drops and equal or different forward blocking voltages for the same current

Solution:

269. A single phase full bridge inverter for R-L loads needs

A. 4 thyristors

B. 4 thyristors and 4 diodes

C. 4 thyristors and 2 diodes

D. 8 thyristors

Solution:

270. In the basic series inverter circuit, the source current has

A. low harmonic content

B. high harmonic content

C. low or high harmonic content depending on firing angle

D. zero harmonic content

Solution:

271. Thyristors connected in series need static and dynamic stabilizing circuits.

A. True

B. False

C. none

D. all

Solution:

272. When a UJT is used as a relaxation oscillator the current should be

A. less than Ip

B. more than Iv

C. more than Ip but less than Iv

D. negative

Solution:

273. In a single phase full wave regulator feeding a resistive load, the average current over one full cycle

A. is always zero

B. cannot be zero

C. may be sometimes zero

D. is always positive

Solution:

274. Which of these devices have four layers?

A. UJT

B. SCR

C. TRIAC

D. SCR and TRIAC

Solution:

275. When UJT is used for thyristor gate signal, the output of UJT is

A. sine wave

B. square wave

C. saw tooth wave

D. either (a) or (c)

Solution:

276. In rectifier circuits, the rms value of ac component of output voltage is equal to

A. Vrms

B. 0.5 Vrms

C. (Vrms – Vdc)0.5

D. (Vrms2– Vdc2)0.5

Solution:

277. A UJT exhibits negative resistance characteristics when

A. Current is less than valley current

B. Current is less than peak current

C. Current is more than peak current but less than valley current

D. None of the above

Solution:

278. In rectifier circuits, ripple factor RF and form factor FF are related as

A. RF = (FF2– 1)0.5

B. RF = FF

C. RF = FF – 1

D. RF = (FF – 1)0.5

Solution:

### Complete List of MCQ in Electronics Engineering per topic

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