MCQOPTIONS
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MCQOPTIONS
This section includes 21 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. |
If it is desired to approximate the efficiency of an induction motor operating at slip ‘s’, then its efficiency is given by? |
| A. | 1-s/1+s |
| B. | 1/1+s |
| C. | s/s+1 |
| D. | s/1-s |
| Answer» B. 1/1+s | |
| 2. |
A delta connected capacitance bank is preferred over a star connected bank. This is done to ensure _________ |
| A. | lesser capacitance |
| B. | easy calculation |
| C. | easier connection |
| D. | all of the mentioned |
| Answer» B. easy calculation | |
| 3. |
A star connected capacitor bank is connected to the induction motor having capacitance C and VA rating as VAs. If the capacitor bank is replaced by a delta bank then? |
| A. | C = C/3, VA = VAs |
| B. | C = 3C, VA = VAs |
| C. | C = C, VA = VAs/3 |
| D. | C = C/3, VA = VAs/3 |
| Answer» B. C = 3C, VA = VAs | |
| 4. |
Induction generators will deliver power at _________ |
| A. | leading p.f. |
| B. | lagging p.f. |
| C. | unity p.f. |
| D. | zero p.f. |
| Answer» B. lagging p.f. | |
| 5. |
A 3-phase induction machine is running at super synchronous speed. For the machine to be self excited it _________ |
| A. | draws reactive power from mains |
| B. | draws real power from mains |
| C. | feeds reactive power to mains |
| D. | generates emf by gradual voltage build up |
| Answer» B. draws real power from mains | |
| 6. |
In a 3-phase induction generator which is self excited, load has been increased. To keep the frequency of the generated voltage constant, speed of the induction machine should be _________ |
| A. | increased |
| B. | decreased |
| C. | maintained less than rated synchronous speed |
| D. | maintained more than rated synchronous speed |
| Answer» B. decreased | |
| 7. |
At standstill the equivalent of the 3-phase induction motor is similar to _________ |
| A. | short-circuited two winding transformer |
| B. | open circuit two winding transformer |
| C. | stand still synchronous motor |
| D. | none of the mentioned |
| Answer» B. open circuit two winding transformer | |
| 8. |
The actual rotor resistance referred to the stator if the induction motor is? |
| A. | r2 |
| B. | (r2)/s |
| C. | (r2)/(1-s) |
| D. | (r2)*(1-s)/s |
| Answer» B. (r2)/s | |
| 9. |
The electrical anlogous of the mechanical load in the induction machine is given by? |
| A. | (r2)*(1-s)/s |
| B. | (r2) |
| C. | (r2)/s |
| D. | (r2)/(1-s) |
| Answer» B. (r2) | |
| 10. |
Rc in the below circuit represents? |
| A. | core loss of induction motor |
| B. | no load losses of induction motor |
| C. | iron losses of induction motor |
| D. | copper losses of induction motor |
| Answer» B. no load losses of induction motor | |
| 11. |
If it is desired to approximate the efficiency of an induction motor operating at slip ‘s’, then its efficiency is given by$ |
| A. | 1-s/1+s |
| B. | 1/1+s |
| C. | s/s+1 |
| D. | s/1-s |
| Answer» B. 1/1+s | |
| 12. |
A delta connected capacitance bank is preferred over a star connected bank. This is done to ensure |
| A. | lesser capacitance |
| B. | easy calculation |
| C. | easier connection |
| D. | all of the mentioned |
| Answer» B. easy calculation | |
| 13. |
A star connected capacitor bank is connected to the induction motor having capacitance C and VA rating as VAs. |
| A. | |
| B. | C = C/3, VA = VAs |
| C. | C = 3C, VA = VAs |
| Answer» B. C = C/3, VA = VAs | |
| 14. |
Induction generators will deliver power at |
| A. | leading p.f. |
| B. | lagging p.f. |
| C. | unity p.f. |
| D. | zero p.f. |
| Answer» B. lagging p.f. | |
| 15. |
A 3-phase induction machine is running at super synchronous speed. For the machine to be self excited, it |
| A. | draws reactive power from mains |
| B. | draws real power from mains |
| C. | feeds reactive power to mains |
| D. | generates emf by gradual voltage build up |
| Answer» B. draws real power from mains | |
| 16. |
In a 3-phase induction generator which is self excited, load has been increased.To keep the frequency of the generated voltage constant, speed of the induction machine should be |
| A. | increased |
| B. | decreased |
| C. | maintained less than rated synchronous speed |
| D. | maintained more than rated synchronous speed |
| Answer» B. decreased | |
| 17. |
At standstill the equivalent of the 3-phase induction motor is similar t? |
| A. | short-circuited two winding transformer |
| B. | open circuit two winding transformer |
| C. | stand still synchronous motor |
| D. | none of the mentioned |
| Answer» B. open circuit two winding transformer | |
| 18. |
The leakage reactance and the rotor resistance are constant throughout the operation in an induction motor. |
| A. | True |
| B. | False |
| Answer» C. | |
| 19. |
The leakage reactances are less than their values at the full load operating conditions. Why? |
| A. | Due to large inrush current during starting |
| B. | Due to very low saturation |
| C. | Due to speed is not same as synchronous speed |
| D. | All of the mentioned |
| Answer» B. Due to very low saturation | |
| 20. |
The actual rotor resistance referred to the stator if the induction motor is |
| A. | r2 |
| B. | (r2)/s |
| C. | (r2)/(1-s) |
| D. | (r2)*(1-s)/s |
| Answer» B. (r2)/s | |
| 21. |
The electrical anlogous of the mechanical load in the induction machine is given by |
| A. | (r2)*(1-s)/s |
| B. | (r2) |
| C. | (r2)/s |
| D. | (r2)/(1-s) |
| Answer» B. (r2) | |