MCQOPTIONS
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MCQOPTIONS
This section includes 15 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. |
A dc shunt motor is running at 1000 rpm at the rated load torque. If few of the field windings get shot circuited then the __________ |
| A. | motor speed will increase and more armature current is drawn |
| B. | motor speed will decrease and more armature current is drawn |
| C. | motor speed will increase and lesser armature current is drawn |
| D. | motor speed will decrease and lesser armature current is drawn |
| Answer» B. motor speed will decrease and more armature current is drawn | |
| 2. |
A dc shunt motor is running at 1000 rpm at the rated load torque. If we reverse the supply terminals, then the __________ |
| A. | direction of rotation reverses and commutation will be unaffected |
| B. | direction of rotation will be same and commutation will be unaffected |
| C. | direction of ration reverses and commutation will be affected |
| D. | direction of ration will be same and commutation will be affected |
| Answer» C. direction of ration reverses and commutation will be affected | |
| 3. |
A dc shunt motor is running at 1000 rpm at the rated load torque. If we reverse the filed winding terminals, then the __________ |
| A. | direction of rotation reverses and commutation will be unaffected |
| B. | direction of rotation will be same and commutation will be unaffected |
| C. | direction of ration reverses and commutation will be affected |
| D. | direction of ration will be same and commutation will be affected |
| Answer» B. direction of rotation will be same and commutation will be unaffected | |
| 4. |
A dc shunt motor is connected to the source through 3-point starter. If the field id kept open and starter handle is moved from off to on position, then __________ |
| A. | motor will not start |
| B. | armature will draw large current from source |
| C. | no sparking would occur |
| D. | all of the mentioned |
| Answer» E. | |
| 5. |
The correct positioning of the windings in the below diagrams is? |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11a.png"><img alt="The positioning of the windings - option a" class="alignnone size-full wp-image-160812" height="150" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11a.png" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11b.png"><img alt="The positioning of the windings - option b" class="alignnone size-full wp-image-160813" height="183" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11b.png" width="300"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11c.png"><img alt="The positioning of the windings - option c" class="alignnone size-full wp-image-160814" height="158" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11c.png" width="300"/></a> |
| D. | Any of the mentioned |
| Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11b.png"><img alt="The positioning of the windings - option b" class="alignnone size-full wp-image-160813" height="183" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q11b.png" width="300"/></a> | |
| 6. |
Compensating winding has an advantage of __________ |
| A. | eliminating flux distortion |
| B. | importing speed of response |
| C. | protecting overloading |
| D. | any of the mentioned |
| Answer» B. importing speed of response | |
| 7. |
Compensating windings are embedded in pole faces and having the same polarity as that of adjoining armature winding. |
| A. | True |
| B. | False |
| Answer» C. | |
| 8. |
A 100KW, 250 V, 400 A, a long shunt compound generator has an armature resistance of 0.025 ohms. There are 1000 shunt fields turns per pole and 3 series field turns per pole. The series field is connected in a such a fashion that positive armature current produces direct-axis MMF which adds to that of the shunt field. Compute the gross MMF at the rated terminal current when shunt field current is 4.7A and speed is 1150 rpm. |
| A. | 5.9AT |
| B. | 3.5AT |
| C. | 4.7AT |
| D. | 1.2AT |
| Answer» B. 3.5AT | |
| 9. |
The brushes of a dc motor, are shifted by 5 , from the main field axis, then __________ |
| A. | demagnetizing or magnetizing effect may occur depending on machine |
| B. | cross-magnetization will be pronounced |
| C. | both cross-magnetization as well as magnetization and demagnetization will occur |
| D. | none of the mentioned |
| Answer» B. cross-magnetization will be pronounced | |
| 10. |
Which method needed to limit cross-magnetizing effect? |
| A. | by increasing reluctance of cross flux path |
| B. | by chamfering the pole faces |
| C. | by compensating winding |
| D. | any of the mentioned |
| Answer» B. by chamfering the pole faces | |
| 11. |
The flux distortion caused by cross magnetizing armature reaction is more pronounced in a __________ |
| A. | dc shunt motor |
| B. | dc series motor |
| C. | any of the mentioned |
| D. | differential Compound Motors |
| Answer» B. dc series motor | |
| 12. |
The air-gap flux density waveform has decreased flux under one pole tip and measured under the other is due to __________ |
| A. | cross magnetization |
| B. | magnetization |
| C. | demagnetization |
| D. | saturation of iron magnetic circuit |
| Answer» B. magnetization | |
| 13. |
Armature reaction in a dc machine is __________ |
| A. | cross magnetizing in nature |
| B. | magnetizing in nature |
| C. | demagnetizing in nature |
| D. | none of the mentioned |
| Answer» B. magnetizing in nature | |
| 14. |
The space distribution of flux produced in a DC machine is? |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q2a.png"><img alt="The space distribution of flux produced in a DC machine - option a" class="alignnone size-full wp-image-160809" height="215" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q2a.png" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q2b.png"><img alt="The space distribution of flux produced in a DC machine - option b" class="alignnone size-full wp-image-160810" height="194" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q2b.png" width="215"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q2c.png"><img alt="The space distribution of flux produced in a DC machine - option c" class="alignnone size-full wp-image-160811" height="170" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-dc-machine-mmf-flux-density-q2c.png" width="300"/></a> |
| D. | None of the mentioned |
| Answer» E. | |
| 15. |
The armature mmf affects __________ |
| A. | commutation |
| B. | generated voltage |
| C. | torque |
| D. | any of the mentioned |
| Answer» B. generated voltage | |