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.
| 501. |
The power developed by a synchronous motor will be maximum when the load angle is |
| A. | zero |
| B. | 45° |
| C. | 90° |
| D. | 120° |
| Answer» D. 120¬¨‚àû | |
| 502. |
If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is# |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 6 |
| Answer» C. 4 | |
| 503. |
A synchronous motor can be made self starting by providing |
| A. | Damper winding on rotor poles |
| B. | Damper winding on stator |
| C. | Damper winding on stator as well as rotor poles |
| D. | None of the above |
| Answer» E. | |
| 504. |
The back e.m.f. in the stator of a synchronous motor depends on |
| A. | number of poles |
| B. | flux density |
| C. | rotor speed |
| D. | rotor excitation |
| Answer» E. | |
| 505. |
A rotory converter can also be run as a |
| A. | d.c. shunt motor |
| B. | d.c. series motor |
| C. | d.c. compound motor |
| D. | induction motor |
| E. | synchronous motor |
| Answer» F. | |
| 506. |
When load on an over-excited or under excited synchronous motor is increased, rate of change of its armature current as compared with that of power factor is |
| A. | more |
| B. | less |
| C. | equal |
| D. | twice |
| Answer» C. equal | |
| 507. |
The back e.m.f. of a synchronous motor depends on |
| A. | speed |
| B. | load |
| C. | load angle |
| D. | all of the above |
| Answer» D. all of the above | |
| 508. |
In which of the following motors the stator and rotor fields rotate simultaneously ? |
| A. | D.C. motor |
| B. | Reluctance motor |
| C. | Universal motor |
| D. | Synchronous motor |
| Answer» E. | |
| 509. |
The ratio of starting torque to running torque in a synchronous motor is |
| A. | zero |
| B. | one |
| C. | two |
| D. | infinity |
| Answer» B. one | |
| 510. |
The net armature voltage of a synchronous motor is equal to the |
| A. | vector sum of Eb and V |
| B. | arithmetic sum of Eb and V |
| C. | arithmetic difference of Eb and V |
| D. | vector difference of Eh and V |
| Answer» E. | |
| 511. |
The armature current of the synchronous motor has higher values for |
| A. | high excitation only |
| B. | low excitation only |
| C. | both (A) and (B) |
| D. | none of the above |
| Answer» D. none of the above | |
| 512. |
The maximum speed variation in a 3-phase synchronous motor is |
| A. | 10 per cent |
| B. | 6 per cent |
| C. | 4 per cent |
| D. | per cent |
| E. | zero |
| Answer» F. | |
| 513. |
If one-phase of a 3-phase synchronous motor is short-circuited, motor |
| A. | will refuse to start |
| B. | will overheat in spots |
| C. | will not come upto speed |
| D. | will fail to pull into step |
| Answer» B. will overheat in spots | |
| 514. |
For V-curves for a synchronous motor the graph is drawn between |
| A. | field current and armature current |
| B. | terminal voltage and load factor |
| C. | power factor and field current |
| D. | armature current and power factor |
| Answer» B. terminal voltage and load factor | |
| 515. |
The percentage slip in case of a synchronous motor is |
| A. | 1% |
| B. | 100% |
| C. | 0.5% |
| D. | zero |
| Answer» E. | |
| 516. |
While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by |
| A. | induction motor torque in field winding |
| B. | induction motor torque in damper winding |
| C. | eddy current and hysteresis torque in pole faces |
| D. | reHetance motor torque due to saliency of the rotor |
| E. | all of the above methods |
| Answer» F. | |
| 517. |
A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as |
| A. | static condenser |
| B. | condenser |
| C. | synchronous condenser |
| D. | none of the above |
| Answer» D. none of the above | |