MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 10 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. |
Power factor of a synchronous motor varies when the ___________ |
| A. | applied voltage is varied |
| B. | load is changed |
| C. | supply frequency and field excitation is changed |
| D. | all of the mentioned |
| Answer» B. load is changed | |
| 2. |
The reactive power output of a synchronous generator is limited by ___________ |
| A. | armature current and field current |
| B. | field current and load angle |
| C. | load angle and prime mover input |
| D. | armature current and prime mover input |
| Answer» B. field current and load angle | |
| 3. |
A synchronous machine is operating at constant load and at unity power factor. If its excitation is increased, then it operates as ___________ |
| A. | generator at lagging p.f |
| B. | motor at lagging p.f |
| C. | absorber of reactive power |
| D. | generator at leading p.f |
| Answer» B. motor at lagging p.f | |
| 4. |
A synchronous machine is operating at constant load and at unity power factor. If its excitation is increased and then it operates as ___________ |
| A. | motor at leading p.f |
| B. | motor at lagging p.f |
| C. | absorber of reactive power |
| D. | generator at leading p.f |
| Answer» B. motor at lagging p.f | |
| 5. |
A 3-phase, 400V, synchronous motor is providing load at 0.8 p.f. lagging. If the field current of the motor is continuously increased, then the _____________ |
| A. | power factor increases and then decreases |
| B. | power factor is not affected |
| C. | power factor decreases upto a certain value of field current and then increases |
| D. | power facor increases simply |
| Answer» B. power factor is not affected | |
| 6. |
In a 3-phase cylindrical-rotor alternator, synchronous reactance is sum of mutual and leakage reactance. |
| A. | True |
| B. | False |
| Answer» C. | |
| 7. |
These days alternators are designed to have larger air gaps for __________ |
| A. | stable parallel operation |
| B. | higher stability limit |
| C. | sinusoidal mmf distribution |
| D. | all of the mentioned |
| Answer» B. higher stability limit | |
| 8. |
A synchronous machine with its field winding on stator and polyphase armature winding on rotor. At steady state, which of the following is not true for its air gap field? |
| A. | stationary w.r.t. stator |
| B. | rotating at double the speed Ns w.r.t. rotor |
| C. | rotating in direction opposite to rotor |
| D. | rotating at Ns w.r.t. rotor |
| Answer» E. | |
| 9. |
Auxiliary method of starting is not possib1e due to the fact that ____________ |
| A. | it can not be started under load |
| B. | it can be only started under load |
| C. | it is less efficient |
| D. | all of the mentioned |
| Answer» B. it can be only started under load | |
| 10. |
Synchronous motors are ___________ |
| A. | not self starting |
| B. | self starting |
| C. | single excited |
| D. | none of the mentioned |
| Answer» B. self starting | |