MCQOPTIONS
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MCQOPTIONS
This section includes 12 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. |
(I) Even at no load a large 3-phase squirrel- cage induction motor is started at reduced voltage than rated. (II) If a large 3 phase squirrel-cage induction motor with no load is started at full voltage, it will be damaged. |
| A. | I is true, II is false |
| B. | I is true and II is also true |
| C. | I is false, II is true |
| D. | I and II are false |
| Answer» B. I is true and II is also true | |
| 2. |
The rotor of 3-phase slip ring induction motor is fed from a 3-phase supply with its stator winding short circuited having rotor rotating clockwise at a speed of Nr, then the _________ |
| A. | speed of air gap field w.r.t. stator is Ns-Nr anticlockwise |
| B. | speed of air gap field w.r.t. stator is Ns-Nr clockwise |
| C. | speed of airgap field w.r.t rotor is Ns clockwise |
| D. | speed of airgap field w.r.t. stator is Ns-Nr clockwise |
| Answer» B. speed of air gap field w.r.t. stator is Ns-Nr clockwise | |
| 3. |
The great advantage of the double squirrel-cage induction motor over single cage rotor is that its _________ |
| A. | efficiency is higher |
| B. | power factor is higher |
| C. | slip is larger |
| D. | starting current is lower |
| Answer» E. | |
| 4. |
An induction motor when started on load, it does not accelerate up to full speed but runs at 1/7th of the rated speed. The motor is said to be _________ |
| A. | Locking |
| B. | Plumming |
| C. | Crawling |
| D. | Cogging |
| Answer» D. Cogging | |
| 5. |
The low no load power factor _________ |
| A. | reduces full load operating pf |
| B. | increases full load operating pf |
| C. | reduces full load excitation voltage |
| D. | increases full load excitation voltage |
| Answer» B. increases full load operating pf | |
| 6. |
Mechanically air gaps in induction motor are kept very low to avoid _________ |
| A. | lower power factor |
| B. | lagging nature |
| C. | magnetizing current |
| D. | all of the mentioned |
| Answer» E. | |
| 7. |
At no load induction motor has possible power factor as _________ |
| A. | 0.2 |
| B. | 0.5 |
| C. | 0.65 |
| D. | 0 |
| Answer» B. 0.5 | |
| 8. |
The no load current of the induction motor is high due to _________ |
| A. | long and high reluctance path between stator and rotor |
| B. | mutual flux having moderate reluctance path between stator and rotor |
| C. | leakage flux having low reluctance iron core |
| D. | leakage flux having high reluctance iron core |
| Answer» B. mutual flux having moderate reluctance path between stator and rotor | |
| 9. |
The no load current of the transformer is very less due to _________ |
| A. | mutual flux having low reluctance iron core |
| B. | mutual flux having high reluctance iron core |
| C. | leakage flux having low reluctance iron core |
| D. | leakage flux having high reluctance iron core |
| Answer» B. mutual flux having high reluctance iron core | |
| 10. |
The rated current in induction motor for a three phase system is 100A. What can be the no load estimated current for the machine? |
| A. | 12 A |
| B. | 20 A |
| C. | 30 A |
| D. | 5 A |
| Answer» B. 20 A | |
| 11. |
A 3-phase induction motor with its rotor blocked behaves similar to a _________ |
| A. | transformer under short circuit of secondary terminals |
| B. | transformer under open circuit of secondary |
| C. | synchronous motor under slip test |
| D. | synchronous motor under open circuit |
| Answer» B. transformer under open circuit of secondary | |
| 12. |
An induction motor can be said analogous to _________ |
| A. | transformer |
| B. | synchronous motor |
| C. | universal motor |
| D. | stepper motor |
| Answer» B. synchronous motor | |