MCQOPTIONS
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MCQOPTIONS
This section includes 12 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. |
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 | |
| 2. |
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 | |
| 3. |
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 | |
| 4. |
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 | |
| 5. |
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. | |
| 6. |
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 | |
| 7. |
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 | |
| 8. |
The reactive power in synchronous machine is proportional to __________ |
| A. | torque |
| B. | excitation |
| C. | sin |
| D. | all of the mentioned |
| Answer» C. sin | |
| 9. |
Active power in synchronous machine is proportional to __________ |
| A. | torque |
| B. | excitation |
| C. | sin |
| D. | all of the mentioned |
| Answer» B. excitation | |
| 10. |
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 | |
| 11. |
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 | |
| 12. |
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 | |