MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 28 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Squirrel cage bars placed in the rotor pole faces of a 3-phase alternator help in reducing hunting. |
| A. | I, II |
| B. | III |
| C. | I, II, III |
| D. | none of the mentionedView Answer |
| Answer» B. III | |
| 2. |
To start the synchronous motor, its field winding should be __________ |
| A. | short circuited |
| B. | kept open |
| C. | connected to dc excitation source |
| D. | any of the mentioned |
| Answer» B. kept open | |
| 3. |
During the starting of the 3-phase synchronous motor by damper bars, the field winding is usually short circuited so that starting torque is equal to __________ |
| A. | induction motor torque plus an additional torque produced by short circuited field winding |
| B. | induction motor torque |
| C. | electromagnetic torque |
| D. | reluctance torque due to rotor saliency |
| Answer» B. induction motor torque | |
| 4. |
For running a 750 kW compressor, a synchronous motor is preferred because of __________ |
| A. | (ii), (iii) |
| B. | (i), (ii), (iv) |
| C. | (i), (ii), (iii), (iv) |
| D. | (iii), (iv)View Answer |
| Answer» B. (i), (ii), (iv) | |
| 5. |
The power load angle characteristic as maximum for a load angle of __________ |
| A. | 90° |
| B. | 45° |
| C. | more than 90° |
| D. | 180° |
| Answer» B. 45° | |
| 6. |
If the 3-phase alternator has 4 poles and has synchronous speed of 120 rad/s. Then the mechanical speed in rad/sec is? |
| A. | 60 |
| B. | 240 |
| C. | 120 |
| D. | 30 |
| Answer» B. 240 | |
| 7. |
Reactive power flow in synchronous machine can be controlled by __________ |
| A. | varying field excitation |
| B. | varying field current |
| C. | varying field flux |
| D. | any of the mentioned |
| Answer» E. | |
| 8. |
If the synchronous machine is loaded from floating conditions, the synchronous motor begins to operate at __________ |
| A. | leading p.f |
| B. | lagging p.f |
| C. | unity p.f |
| D. | zero p.f |
| Answer» C. unity p.f | |
| 9. |
If the synchronous machine is loaded from floating conditions, the alternator begins to operate at __________ |
| A. | leading p.f |
| B. | lagging p.f |
| C. | unity p.f |
| D. | zero p.f |
| Answer» B. lagging p.f | |
| 10. |
The reactive power in synchronous machine is proportional to __________ |
| A. | torque |
| B. | excitation |
| C. | sinϕ |
| D. | all of the mentioned |
| Answer» C. sinϕ | |
| 11. |
Active power in synchronous machine is proportional to __________ |
| A. | torque |
| B. | excitation |
| C. | sinϕ |
| D. | all of the mentioned |
| Answer» B. excitation | |
| 12. |
At steady state operation in a 3-phase synchronous generator. (where Tem is developed electromagnetic torque developed in the machine and Tpm is the prime mover torque.) |
| A. | Tem = Tpm |
| B. | Tem > Tpm |
| C. | Tem < Tpm |
| D. | can not be coupled |
| Answer» B. Tem > Tpm | |
| 13. |
If the field poles are ahead of resultant mmf, then the 3-phase synchronous machine is operating as ___________ |
| A. | generator |
| B. | motor |
| C. | reluctance motor |
| D. | any of the mentioned |
| Answer» B. motor | |
| 14. |
Floating of synchronous machine on infinite bus means ___________ |
| A. | Fa = 0 and machine neither generator nor motor |
| B. | Fa is not zero and machine neither generator nor motor |
| C. | Fa = 0 and machine is not excited |
| D. | frequency is zero |
| Answer» B. Fa is not zero and machine neither generator nor motor | |
| 15. |
IF_THE_3-PHASE_ALTERNATOR_HAS_4_POLES_AND_HAS_SYNCHRONOUS_SPEED_OF_120_RAD/S.?$ |
| A. | |
| B. | 60 |
| C. | 240 |
| Answer» B. 60 | |
| 16. |
For running a 750 kW compressor, a synchronous motor is preferred because of$ |
| A. | lower noise |
| B. | faster build up of pressure |
| C. | better power factor |
| D. | low starting torque |
| Answer» B. faster build up of pressure | |
| 17. |
The_power_load_angle_characteristic_as_maximum_for_a_load_angle_of$ |
| A. | 90° |
| B. | 45° |
| C. | more than 90° |
| D. | 180° |
| Answer» B. 45¬¨¬®‚Äö√†√ª | |
| 18. |
To start the synchronous motor, its field winding should be |
| A. | short circuited |
| B. | kept open |
| C. | connected to dc excitation source |
| D. | any of the mentioned |
| Answer» B. kept open | |
| 19. |
During the starting of the 3-phase synchronous motor by damper bars, the field winding is usually short circuited so that starting torque is equal to |
| A. | induction motor torque plus an additional torque produced by short circuited field winding |
| B. | induction motor torque |
| C. | electromagnetic torque |
| D. | reluctance torque due to rotor saliency |
| Answer» B. induction motor torque | |
| 20. |
A poly phase synchronous motor will be used for the load of ______ over poly phase induction motor. |
| A. | 600 kW 500 rpm |
| B. | 600 kW 1500 rpm |
| C. | 600 kW 3500 rpm |
| D. | 600 kW 1200 rpm |
| Answer» B. 600 kW 1500 rpm | |
| 21. |
Reactive power flow in synchronous machine can be controlled b? |
| A. | varying field excitation |
| B. | varying field current |
| C. | varying field flux |
| D. | any of the mentioned |
| Answer» E. | |
| 22. |
If the synchronous machine is loaded from floating conditions, the synchronous motor begins to operate at |
| A. | leading p.f |
| B. | lagging p.f |
| C. | unity p.f |
| D. | zero p.f |
| Answer» C. unity p.f | |
| 23. |
If the synchronous machine is loaded from floating conditions, the alternator begins to operate at |
| A. | leading p.f |
| B. | lagging p.f |
| C. | unity p.f |
| D. | zero p.f |
| Answer» B. lagging p.f | |
| 24. |
The reactive power in synchronous machine is proportional to |
| A. | torque |
| B. | excitation |
| C. | sinϕ |
| D. | all of the mentioned |
| Answer» C. sin‚âà√¨‚àö√ò | |
| 25. |
Active power in synchronous machine is proportional to |
| A. | torque |
| B. | excitation |
| C. | sinϕ |
| D. | all of the mentioned |
| Answer» B. excitation | |
| 26. |
At steady state operation in a 3-phase synchronous generator |
| A. | Tem = Tpm |
| B. | Tem > Tpm |
| C. | Tem < Tpm |
| D. | can not be coupled |
| Answer» B. Tem > Tpm | |
| 27. |
If the field poles are ahead of resultant mmf, then the 3-phase synchronous machine is operating as |
| A. | generator |
| B. | motor |
| C. | reluctance motor |
| D. | any of the mentioned |
| Answer» B. motor | |
| 28. |
Floating of synchronous machine on infinite bus means |
| A. | Fa = 0 and machine neither generator nor motor |
| B. | Fa is not zero and machine neither generator nor motor |
| C. | Fa = 0 and machine is not excited |
| D. | frequency is zero |
| Answer» B. Fa is not zero and machine neither generator nor motor | |