MCQOPTIONS
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MCQOPTIONS
This section includes 517 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 351. |
The coupling angle or load angle of synchronous motor is defined as the angle between the%! |
| A. | rotor and stator teeth |
| B. | rotor and the stator poles of opposite polarity |
| C. | rotor and the stator poles of the same polarity |
| D. | none of the above |
| Answer» C. rotor and the stator poles of the same polarity | |
| 352. |
Stability of a synchronous machine%! |
| A. | decreases with increase in its excitation |
| B. | increases with increase in its excitation |
| C. | remains unaffected with increase in excitation |
| D. | any of the above |
| Answer» C. remains unaffected with increase in excitation | |
| 353. |
A synchronous motor working at leading power factor can be used as%! |
| A. | voltage booster |
| B. | phase advancer |
| C. | noise generator |
| D. | mechanical synchronizer |
| Answer» C. noise generator | |
| 354. |
While starting a synchronous motor by induction motor action, field winding is usually%! |
| A. | connected to D.C. supply |
| B. | short-circuited by low resistance |
| C. | kept open-circuited |
| D. | none of the above |
| Answer» C. kept open-circuited | |
| 355. |
Change of D.C. excitation of a synchronous motor changes%! |
| A. | Applied voltage of the motor |
| B. | Motor speed |
| C. | Power factor of power drawn by the motor |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 356. |
If the field of a synchronous motor is underexcited, the power factor will be%! |
| A. | zero |
| B. | unity |
| C. | lagging |
| D. | leading |
| Answer» D. leading | |
| 357. |
A synchronous motor can be started by%! |
| A. | pony motor |
| B. | D.C. compound motor |
| C. | providing damper winding |
| D. | any of the above |
| Answer» E. | |
| 358. |
The working of a synchronous motor is similar to%! |
| A. | gear train arrangement |
| B. | transmission of mechancial power by shaft |
| C. | distribution transformer |
| D. | turbine |
| Answer» C. distribution transformer | |
| 359. |
A synchronous motor running with normal excitation adjusts to load increases essentially by increase in%! |
| A. | back e.m.f. |
| B. | armature current |
| C. | power factor |
| D. | torque angle |
| Answer» C. power factor | |
| 360. |
In a synchronous motor, the damping winding is generally used to%! |
| A. | prevent hunting and provide the starting torque |
| B. | reduce the eddy currents |
| C. | provide starting torque only |
| D. | reduce noise level |
| Answer» B. reduce the eddy currents | |
| 361. |
If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will%! |
| A. | stop |
| B. | run as induction motor |
| C. | function as static condenser |
| D. | burn with dense smoke |
| Answer» B. run as induction motor | |
| 362. |
A synchronous motor can operate at%! |
| A. | lagging power factor only |
| B. | leading power factor only |
| C. | unity power factor only |
| D. | lagging, leading and unity power factors |
| Answer» E. | |
| 363. |
A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will%! |
| A. | remain same |
| B. | go down |
| C. | improve |
| D. | none of the above |
| Answer» D. none of the above | |
| 364. |
In case one phase of a three-phase synchronous motor is short-circuited the motor will%! |
| A. | not start |
| B. | run at 2/3 of synchronous speed |
| C. | run with excessive vibrations |
| D. | take less than the rated load |
| Answer» B. run at 2/3 of synchronous speed | |
| 365. |
The duration of sudden short-circuit test on a synchronous motor is usually about%! |
| A. | one hour |
| B. | one minute |
| C. | one second |
| D. | none of the above |
| Answer» D. none of the above | |
| 366. |
The efficiency of a properly designed synchronous motor will usually fall in range%! |
| A. | 60 to 70% |
| B. | 75 to 80% |
| C. | 85 to 95% |
| D. | 99 to 99.5% |
| Answer» D. 99 to 99.5% | |
| 367. |
The size of a synchronous motor decreases with the increase in%! |
| A. | flux density |
| B. | horse power rating |
| C. | speed |
| D. | all of the above |
| Answer» B. horse power rating | |
| 368. |
*$_The size of a synchronous motor decreases with the increase in? |
| A. | flux density |
| B. | horse power rating |
| C. | speed |
| D. | all of the above |
| Answer» B. horse power rating | |
| 369. |
*$_The duration of sudden short-circuit test on a synchronous motor is usually about? |
| A. | one hour |
| B. | one minute |
| C. | one second |
| D. | none of the above |
| Answer» D. none of the above | |
| 370. |
*$_In case one phase of a three-phase synchronous motor is short-circuited the motor will? |
| A. | not start |
| B. | run at 2/3 of synchronous speed |
| C. | run with excessive vibrations |
| D. | take less than the rated load |
| Answer» B. run at 2/3 of synchronous speed | |
| 371. |
*$_If the field of a synchronous motor is underexcited, the power factor will be? |
| A. | zero |
| B. | unity |
| C. | lagging |
| D. | leading |
| Answer» D. leading | |
| 372. |
*$_The efficiency of a properly designed synchronous motor will usually fall in range? |
| A. | 60 to 70% |
| B. | 75 to 80% |
| C. | 85 to 95% |
| D. | 99 to 99.5% |
| Answer» D. 99 to 99.5% | |
| 373. |
*$_Change of D.C. excitation of a synchronous motor changes? |
| A. | Applied voltage of the motor |
| B. | Motor speed |
| C. | Power factor of power drawn by the motor |
| D. | Any of the above |
| Answer» D. Any of the above | |
| 374. |
*$_A synchronous motor can be started by? |
| A. | pony motor |
| B. | D.C. compound motor |
| C. | providing damper winding |
| D. | any of the above |
| Answer» E. | |
| 375. |
*$_A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will? |
| A. | remain same |
| B. | go down |
| C. | improve |
| D. | none of the above |
| Answer» D. none of the above | |
| 376. |
*$_A synchronous motor can operate at? |
| A. | lagging power factor only |
| B. | leading power factor only |
| C. | unity power factor only |
| D. | lagging, leading and unity power factors |
| Answer» E. | |
| 377. |
*$_If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will? |
| A. | stop |
| B. | run as induction motor |
| C. | function as static condenser |
| D. | burn with dense smoke |
| Answer» B. run as induction motor | |
| 378. |
*$_In a synchronous motor, the damping winding is generally used to? |
| A. | prevent hunting and provide the starting torque |
| B. | reduce the eddy currents |
| C. | provide starting torque only |
| D. | reduce noise level |
| Answer» B. reduce the eddy currents | |
| 379. |
*$_A synchronous motor running with normal excitation adjusts to load increases essentially by increase in? |
| A. | back e.m.f. |
| B. | armature current |
| C. | power factor |
| D. | torque angle |
| Answer» C. power factor | |
| 380. |
*$_If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to? |
| A. | increase in both armature current and power factor angle |
| B. | increase in back e.m.f. but decrease in armature current |
| C. | increase in both armature current and power factor which is lagging |
| D. | increase in torque angle but decrease in back e.m.f. |
| Answer» B. increase in back e.m.f. but decrease in armature current | |
| 381. |
*$_The construction of a synchronous motor resembles? |
| A. | a series motor |
| B. | an induction motor |
| C. | an alternator |
| D. | a rotary converter |
| Answer» D. a rotary converter | |
| 382. |
*/*_In a synchronous motor, the breakdown torque is? |
| A. | directly proportional to applied voltage |
| B. | directly proportional to the square of the applied voltage |
| C. | inversely proportional to applied voltage |
| D. | none of the above |
| Answer» B. directly proportional to the square of the applied voltage | |
| 383. |
*/*_While starting a synchronous motor by induction motor action, field winding is usually? |
| A. | connected to D.C. supply |
| B. | short-circuited by low resistance |
| C. | kept open-circuited |
| D. | none of the above |
| Answer» C. kept open-circuited | |
| 384. |
*/*_A synchronous motor working at leading power factor can be used as? |
| A. | voltage booster |
| B. | phase advancer |
| C. | noise generator |
| D. | mechanical synchronizer |
| Answer» C. noise generator | |
| 385. |
*/*_Stability of a synchronous machine? |
| A. | decreases with increase in its excitation |
| B. | increases with increase in its excitation |
| C. | remains unaffected with increase in excitation |
| D. | any of the above |
| Answer» C. remains unaffected with increase in excitation | |
| 386. |
*/*_The working of a synchronous motor is similar to? |
| A. | gear train arrangement |
| B. | transmission of mechancial power by shaft |
| C. | distribution transformer |
| D. | turbine |
| Answer» C. distribution transformer | |
| 387. |
*/*_The coupling angle or load angle of synchronous motor is defined as the angle between the? |
| A. | rotor and stator teeth |
| B. | rotor and the stator poles of opposite polarity |
| C. | rotor and the stator poles of the same polarity |
| D. | none of the above |
| Answer» C. rotor and the stator poles of the same polarity | |
| 388. |
*/*_The synchronous motor is not inherently self-starting because? |
| A. | the force required to accelerate the rotor to the synchronous speed in an instant is absent |
| B. | the starting device to accelerate the rotor to near synchronous speed is absent |
| C. | a rotating magnetic field does not have enough poles |
| D. | the rotating magnetic field is produced by only 50 Hz frequency currents |
| Answer» B. the starting device to accelerate the rotor to near synchronous speed is absent | |
| 389. |
*/*_Synchronous motors are generally not self-starting because? |
| A. | the direction of rotation is not fixed |
| B. | the direction of instantaneous torque reverses after half cycle |
| C. | startes cannot be used on these machines |
| D. | starting winding is not provided on the machines |
| Answer» C. startes cannot be used on these machines | |
| 390. |
*/*_In a synchronous motor, the armature current has large values for? |
| A. | high excitation only |
| B. | low excitation only |
| C. | both high and low excitation |
| D. | none of the above |
| Answer» D. none of the above | |
| 391. |
*/*_Which of the following losses, in a synchronous motor, does not vary with load?? |
| A. | Windage loss |
| B. | Copper losses |
| C. | Any of the above |
| D. | None of the above |
| Answer» B. Copper losses | |
| 392. |
*/*_The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of? |
| A. | zero degree |
| B. | two degrees |
| C. | five degrees |
| D. | ten degrees |
| Answer» D. ten degrees | |
| 393. |
*/*_An over-excited synchronous motor takes? |
| A. | leading current |
| B. | lagging current |
| C. | both (A) and (B) |
| D. | none of the above |
| Answer» B. lagging current | |
| 394. |
*/*_The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as? |
| A. | pull-up torque |
| B. | pull-in torque |
| C. | pull-out torque |
| D. | none of the above |
| Answer» C. pull-out torque | |
| 395. |
*/*_The induced e.m.f. in a synchronous motor working on leading power factor will be? |
| A. | more than the supply voltage |
| B. | less than the supply voltage |
| C. | equal to the supply voltage |
| D. | none of the above |
| Answer» B. less than the supply voltage | |
| 396. |
*/*_If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then? |
| A. | it runs at a slower speed |
| B. | the motor stops |
| C. | it continues to run at the same speed |
| D. | it runs at a very high speed |
| Answer» C. it continues to run at the same speed | |
| 397. |
*/*_When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop? |
| A. | inductor motor torque |
| B. | induction generator torque |
| C. | synchronous motor torque |
| D. | d.c. motor toque |
| Answer» C. synchronous motor torque | |
| 398. |
*/*_Exciters of synchronous machines are? |
| A. | d.c. shunt machines |
| B. | d.c. series machines |
| C. | d.c. compound machines |
| D. | any of the above |
| Answer» B. d.c. series machines | |
| 399. |
*/*_In a synchronous motor, damper windings are provided on? |
| A. | stator frame |
| B. | rotor shaft |
| C. | pole faces |
| D. | none of the above |
| Answer» D. none of the above | |
| 400. |
*/*_A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because? |
| A. | Speed of the motor is reduced |
| B. | Power factor is decreased |
| C. | Eb (back e.m.f.) becomes less than V (applied voltage) |
| D. | Er (net resultant voltage) in armature is increased |
| Answer» E. | |