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. |
Which motor can conveniently operate at lagging as well as leading power factor? |
| A. | Synchronous motor |
| B. | Slip ring induction motor |
| C. | Squirrel cage induction motor |
| D. | Stepper motor |
| Answer» B. Slip ring induction motor | |
| 2. |
Variation in the dc excitation of a synchronous motor causes variation in ___________ |
| A. | armature current and power factor |
| B. | power factor |
| C. | armature current |
| D. | speed |
| Answer» B. power factor | |
| 3. |
In a synchronous motor the back emf peak set up in the stator depends on ___________ |
| A. | rotor excitation |
| B. | supply voltage |
| C. | rotor speed |
| D. | load on the motor |
| Answer» B. supply voltage | |
| 4. |
The operation of a synchronous motor operating on constant excitation across infinite bus will not be stable if power angle ? |
| A. | exceeds internal angle |
| B. | is less than |
| C. | is more than /2 |
| D. | is less than /2 |
| Answer» B. is less than | |
| 5. |
Electromagnetic torque is present in rotating machines when ____________ |
| A. | both stator and rotor windings carry current |
| B. | rotor windings carry current |
| C. | stator windings carry current |
| D. | any of the mentioned |
| Answer» B. rotor windings carry current | |
| 6. |
For a 4-pole 3 phase, 400V alternator has synchronizing power of 300 units. Then the synchronizing power per mechanical degree is? |
| A. | 300 |
| B. | 1200 |
| C. | 900 |
| D. | 600 |
| Answer» B. 1200 | |
| 7. |
Which of the following is/are used in synchronous machines to maintain mechanical stability? |
| A. | Damper winding |
| B. | Interpole winding |
| C. | Compensating winding |
| D. | Equalizer rings |
| Answer» B. Interpole winding | |
| 8. |
Which of the following makes synchronizing power to come to play in the machine? |
| A. | Disturbance in power mover |
| B. | Disturbance in field current |
| C. | Disturbance in load |
| D. | All of the mentioned |
| Answer» B. Disturbance in field current | |
| 9. |
Synchronizing power is __________ |
| A. | transient in nature |
| B. | steady state in nature |
| C. | pulsating at small frequencies |
| D. | constant for a machine |
| Answer» B. steady state in nature | |
| 10. |
As load angle is increased, degree of stability __________ |
| A. | reduces |
| B. | increases |
| C. | remains same |
| D. | no change in stability |
| Answer» B. increases | |
| 11. |
An over excited synchronous machine is more stable than under excited. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 12. |
Large stiffness coefficient represents ____________ |
| A. | motor speed remains practically constant |
| B. | large fluctuations due to mechanical load |
| C. | motor speed is variable to changes |
| D. | no such significance with speed |
| Answer» B. large fluctuations due to mechanical load | |
| 13. |
The coupling angle or load angle of a synchronous motor is defined as the space angle between __________ |
| A. | rotor and stator poles of opposite polarity |
| B. | rotor and stator poles of same polarity |
| C. | rotor and stator teeth |
| D. | rotor and resultant magnetic field |
| Answer» B. rotor and stator poles of same polarity | |