McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering , Electronics and Communication Engineering .
| 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 |
| Answer» C. two 3 phase full converters connected in antiparallel | |
| 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) |
| Answer» D. Both (b) and (c) | |
| 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 |
| Answer» A. appears across only one junction | |
| 254. |
In sinusoidal PWM for inverters the width of different pulses are not the same. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» A. True | |
| 255. |
The symbol in figure is for |
| A. | UJT |
| B. | PUT |
| C. | SCS |
| D. | SBS |
| Answer» B. PUT | |
| 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 |
| Answer» C. 8 thyristors and 4 diodes | |
| 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° |
| Answer» C. firing angle is more than 60° | |
| 258. |
The circuit in figure is for |
| A. | resonant commutation |
| B. | line commutation |
| C. | auxiliary commutation |
| D. | complementary commutation |
| Answer» D. complementary commutation | |
| 259. |
The main utility of SCR is due to |
| A. | gate triggering |
| B. | high temperature triggering |
| C. | triggering |
| D. | high breakdown voltage |
| Answer» A. gate triggering | |
| 260. |
The symbol in figure is for |
| A. | SUS |
| B. | SBS |
| C. | Shockley diode |
| D. | UJT |
| Answer» C. Shockley diode | |
| 261. |
he circuit in figure is for |
| A. | resonant commutation |
| B. | self commutation |
| C. | load commutation |
| D. | auxiliary commutation |
| Answer» B. self commutation | |
| 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 |
| Answer» C. 2 thyristors and two diodes | |
| 263. |
In a single phase semi-converter the number of thyristors is |
| A. | 16 |
| B. | 8 |
| C. | 4 |
| D. | 2 |
| Answer» D. 2 | |
| 264. |
Which of these commutation methods uses two leads? |
| A. | Class A |
| B. | Class B |
| C. | Class C |
| D. | Class D |
| Answer» D. Class D | |
| 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 |
| Answer» A. both these methods are based on entirely different principles | |
| 266. |
In a series inverter |
| A. | the commutating elements carry full load current |
| B. | the commutating elements carry upto 50% of load current |
| C. | the commutating elements do not carry load current |
| D. | any of the above |
| Answer» A. the commutating elements carry full load current | |
| 267. |
Which of these devices is used in relaxation oscillator? |
| A. | UJT |
| B. | SCR |
| C. | DIAC |
| D. | TRIAC |
| Answer» A. UJT | |
| 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 voltage's for the same current |
| Answer» D. may have equal or different on state voltage drops and equal or different forward blocking voltage's for the same current | |
| 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 |
| Answer» B. 4 thyristors and 4 diodes | |
| 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 |
| Answer» B. high harmonic content | |
| 271. |
Thyristors connected in series need static and dynamic stabilizing circuits. |
| A. | True |
| B. | False |
| C. | none |
| D. | all |
| Answer» A. True | |
| 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 |
| Answer» C. more than Ip but less than Iv | |
| 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 |
| Answer» A. is always zero | |
| 274. |
Which of these devices have four layers? |
| A. | UJT |
| B. | SCR |
| C. | TRIAC |
| D. | SCR and TRIAC |
| Answer» B. SCR | |
| 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) |
| Answer» C. saw tooth wave | |
| 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 |
| Answer» D. (Vrms2- Vdc2)0.5 | |
| 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 |
| Answer» C. Current is more than peak current but less than valley current | |
| 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 |
| Answer» A. RF = (FF2- 1)0.5 | |
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