MCQOPTIONS
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MCQOPTIONS
This section includes 13 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. |
Auto transformer method of starting has most acceptable method for the starting of the induction motor due to __________ |
| A. | maximum torque |
| B. | maximum reduction of inrush current |
| C. | variable tapping |
| D. | all of he mentioned |
| Answer» B. maximum reduction of inrush current | |
| 2. |
For the application requiring high starting torque and minimum starting current, the most suitable starting method will be? |
| A. | Auto transformer starting method |
| B. | Reactance starting method |
| C. | DOL method |
| D. | Star-Delta method |
| Answer» B. Reactance starting method | |
| 3. |
A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by auto transformer method of starting with a tapping ratio of x , then the starting torque will be? |
| A. | x *Tfl |
| B. | x^2 *Tfl |
| C. | 1/x *Tfl |
| D. | no change in the starting current |
| Answer» B. x^2 *Tfl | |
| 4. |
A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by auto transformer method of starting with a tapping ratio of x , then the starting current reduces by? |
| A. | x |
| B. | x^2 |
| C. | 1/x |
| D. | no change in the starting current |
| Answer» C. 1/x | |
| 5. |
Series reactor method of starting has main disadvantage of lowering the starting power. This can be overcome by __________ |
| A. | using series resistance |
| B. | using parallel reactor |
| C. | using parallel resistance |
| D. | using series reactor |
| Answer» B. using parallel reactor | |
| 6. |
Series reactor method of starting has main disadvantage of __________ |
| A. | lowering the starting power |
| B. | increasing the starting current |
| C. | increasing starting torque |
| D. | all of the mentioned |
| Answer» B. increasing the starting current | |
| 7. |
A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by reactance method of starting with a fraction of x , then the starting torque reduces by? |
| A. | x |
| B. | x^2 |
| C. | 1/x |
| D. | no change in the starting current |
| Answer» C. 1/x | |
| 8. |
A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by reactance method of starting with a fraction of x , then the starting current reduces by? |
| A. | x |
| B. | x^2 |
| C. | 1/x |
| D. | no change in the starting current |
| Answer» B. x^2 | |
| 9. |
External methods of induction motor starting is employed to __________ |
| A. | Reduce the voltage |
| B. | Reduce the current |
| C. | Improve efficiency |
| D. | All of the mentioned |
| Answer» B. Reduce the current | |
| 10. |
For a 4-pole, 50 Hz induction motor has starting current as 5 times to that of the full load current working at a speed of 1450rpm. The ratio of starting to full load torque will be? |
| A. | 0.83 |
| B. | 0.17 |
| C. | 0.67 |
| D. | 1 |
| Answer» B. 0.17 | |
| 11. |
Full voltage starting of induction motor may cause __________ |
| A. | dip in the voltages |
| B. | high inrush current |
| C. | high losses |
| D. | all of the mentioned |
| Answer» B. high inrush current | |
| 12. |
Starters are required in the induction motor because __________ |
| A. | of high starting current |
| B. | they are not self starting |
| C. | torque produced is very low at starting to overcome inertia |
| D. | all of the mentioned |
| Answer» B. they are not self starting | |
| 13. |
Voltage induce in the induction motor is highest at __________ |
| A. | starting |
| B. | standstill |
| C. | rated speed |
| D. | any of the mentioned |
| Answer» B. standstill | |