MCQOPTIONS
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MCQOPTIONS
This section includes 35 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. |
The rotor winding for 3-phase slip ring induction motor having delta connected stator must be connected in _________ |
| A. | star |
| B. | delta |
| C. | tertiary |
| D. | any of the mentioned |
| Answer» B. delta | |
| 2. |
In a three phase slip ring induction motor, brushes are connected to _________ |
| A. | external star connected resistors |
| B. | dc supply |
| C. | 3-phase ac supply |
| D. | any of the mentioned |
| Answer» B. dc supply | |
| 3. |
The rotor of th 3-phase induction motor rotates in the same direction as that of stator field. This can be explained by _________ |
| A. | Newton’s laws of motion |
| B. | Farady’s laws of electromagnetic induction |
| C. | Lenz’s law |
| D. | Fleming’s right hand rule |
| Answer» B. Farady’s laws of electromagnetic induction | |
| 4. |
The 3-phase induction motor with rotor circuit open will _________ |
| A. | not run |
| B. | run normally |
| C. | get over heated |
| D. | make noise |
| Answer» B. run normally | |
| 5. |
Stator flux induces emf in the rotor conductors _________ |
| A. | magnitude depending on the load |
| B. | rotating at synchronous speed around stator |
| C. | constant in magnitude |
| D. | none of the mentioned |
| Answer» B. rotating at synchronous speed around stator | |
| 6. |
For a 4-pole, 3-phase induction motor the rotor speed found is 2100 rpm at 50 Hz. Then the phase sequence of the emf generated will be? |
| A. | acb |
| B. | abc |
| C. | no emf will be induced |
| D. | cba |
| Answer» B. abc | |
| 7. |
A 4-pole, 3-phase slip ring induction motor is used as a frequency changer. Its stator is excited from 3-phase, 50 Hz supply. A load requiring 3-phase, 20 Hz supply is connected to the star-connected rotor through three slip-rings of SRIM. At what two speeds the prime mover should drive the rotor of this SRIM? |
| A. | 900 rpm |
| B. | 600 rpm |
| C. | 1500 rpm |
| D. | 0 |
| Answer» B. 600 rpm | |
| 8. |
A properly shunted center zero galvanometer is connected in the rotor circuit of a 6-pole, 50 hz wound rotor induction motor. If the makes 90 complete oscillations in one minute, the rotor speed is? |
| A. | 1000 rpm |
| B. | 970 rpm |
| C. | 950 rpm |
| D. | 930 rpm |
| Answer» C. 950 rpm | |
| 9. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the rotor field w.r.t. stator field is? |
| A. | zero |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» B. 150 rad/s | |
| 10. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the rotor field w.r.t. rotor structure is? |
| A. | 157 rad/s |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» D. 145 rad/s | |
| 11. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the stator field revolving rotor structure is? |
| A. | 157 rad/s |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» D. 145 rad/s | |
| 12. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the stator filed with respect to stator structure is? |
| A. | 157 rad/s |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» B. 150 rad/s | |
| 13. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Rotor frequency is? |
| A. | 2 Hz |
| B. | 50 Hz |
| C. | 52 Hz |
| D. | 58 Hz |
| Answer» B. 50 Hz | |
| 14. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. The full load slip will be? |
| A. | 4% |
| B. | 5% |
| C. | 2.4% |
| D. | 3% |
| Answer» B. 5% | |
| 15. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. The number of poles of this motor is? |
| A. | 4 |
| B. | 6 |
| C. | 5 |
| D. | 2 |
| Answer» B. 6 | |
| 16. |
For a 4 pole three phase induction motor having synchronous speed of 1500 rpm is operating at 1450rpm. The frequency of the induced emf in rotor is? |
| A. | 100 Hz |
| B. | 50 Hz |
| C. | 150 Hz |
| D. | 0 Hz |
| Answer» B. 50 Hz | |
| 17. |
Slip is defined as _________ (Ns as the synchronous speed and Nr is the rotor speed) |
| A. | Ns-Nr/Ns |
| B. | Ns-Nr/Nr |
| C. | Nr-Ns/Ns |
| D. | Ns-Nr/Nsb) Ns-Nr/Nrc) Nr-Ns/Nsd) Ns-Nr |
| Answer» B. Ns-Nr/Nr | |
| 18. |
A_PROPERLY_SHUNTED_CENTER_ZERO_GALVANOMETER_IS_CONNECTED_IN_THE_ROTOR_CIRCUIT_OF_A_6-POLE,_50_HZ_WOUND_ROTOR_INDUCTION_MOTOR._IF_THE_MAKES_90_COMPLETE_OSCILLATIONS_IN_ONE_MINUTE,_THE_ROTOR_SPEED_IS?$ |
| A. | 1000 rpm |
| B. | 970 rpm |
| C. | 950 rpm |
| D. | 930 rpm |
| Answer» C. 950 rpm | |
| 19. |
For a 4-pole, 3-phase induction motor the rotor speed found is 2100 rpm at 50 Hz. Then the phase sequence of the emf generated will be$ |
| A. | acb |
| B. | abc |
| C. | no emf will be induced |
| D. | cba |
| Answer» B. abc | |
| 20. |
A 4-pole, 3-phase slip ring induction motor is used as a frequency changer. Its stator is excited from 3-phase, 50 Hz supply. A load requiring 3-phase, 20 Hz supply is connected to the star-connected rotor through three slip-rings of SRIM.$ |
| A. | |
| B. | 900 rpm |
| C. | 600 rpm |
| Answer» B. 900 rpm | |
| 21. |
The squirrel cage induction motor of 6-pole can be used as ________ induction motor. |
| A. | any number of poles |
| B. | 6 pole |
| C. | 6 or 12 pole |
| D. | integral number of 4 poles |
| Answer» B. 6 pole | |
| 22. |
The rotor winding for 3-phase slip ring induction motor having delta connected stator must be connected in |
| A. | star |
| B. | delta |
| C. | tertiary |
| D. | any of the mentioned |
| Answer» B. delta | |
| 23. |
In a three phase slip ring induction motor, brushes are connected to |
| A. | external star connected resistors |
| B. | dc supply |
| C. | 3-phase ac supply |
| D. | any of the mentioned |
| Answer» B. dc supply | |
| 24. |
The rotor of th 3-phase induction motor rotates in the same direction as that of stator field. This can be explained by |
| A. | Newton’s laws of motion |
| B. | Farady’s laws of electromagnetic induction |
| C. | Lenz’s law |
| D. | Fleming’s right hand rule |
| Answer» B. Farady‚Äö√Ñ√∂‚àö√ë‚àö¬•s laws of electromagnetic induction | |
| 25. |
The 3-phase induction motor with rotor circuit open will |
| A. | not run |
| B. | run normally |
| C. | get over heated |
| D. | make noise |
| Answer» B. run normally | |
| 26. |
Stator flux induces emf in the rotor conductors |
| A. | magnitude depending on the load |
| B. | rotating at synchronous speed around stator |
| C. | constant in magnitude |
| D. | none of the mentioned |
| Answer» B. rotating at synchronous speed around stator | |
| 27. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the rotor field w.r.t. stator field i? |
| A. | zero |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» B. 150 rad/s | |
| 28. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the rotor field w.r.t. rotor structure i? |
| A. | 157 rad/s |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» D. 145 rad/s | |
| 29. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the stator field revolving rotor structure is |
| A. | 157 rad/s |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» D. 145 rad/s | |
| 30. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the stator filed with respect to stator structure is |
| A. | 157 rad/s |
| B. | 150 rad/s |
| C. | 6.28 rad/s |
| D. | 145 rad/s |
| Answer» B. 150 rad/s | |
| 31. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Rotor frequency is |
| A. | 2 Hz |
| B. | 50 Hz |
| C. | 52 Hz |
| D. | 58 Hz |
| Answer» B. 50 Hz | |
| 32. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. The full load slip will be |
| A. | 4% |
| B. | 5% |
| C. | 2.4% |
| D. | 3% |
| Answer» B. 5% | |
| 33. |
A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. The number of poles of this motor is |
| A. | 4 |
| B. | 6 |
| C. | 5 |
| D. | 2 |
| Answer» B. 6 | |
| 34. |
For a 4 pole three phase induction motor having synchronous speed of 1500 rpm is operating at 1450rpm. The frequency of the induced emf in rotor is |
| A. | 100 Hz |
| B. | 50 Hz |
| C. | 150 Hz |
| D. | 0 Hz |
| Answer» B. 50 Hz | |
| 35. |
Slip is defined as (Ns as the synchronous speed and Nr is the rotor speed) |
| A. | Ns-Nr/Ns |
| B. | Ns-Nr/Nr |
| C. | Nr-Ns/Ns |
| D. | Ns-Nr |
| Answer» B. Ns-Nr/Nr | |