Electrical Machines Mock Test 7

10%

Question 1 of 10

1. In a 3-phase cylindrical rotor alternator the _________

armature mmf leads air gap flux and air gap flux leads field flux

field mmf leads air gap flux, air gap flux leads armature flux

field mmf leads air gap flux, air gap flux lags armature flux

armature mmf leads air gap flux and air gap flux lags field flux

Question 1 of 10

Question 2 of 10

2. (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.

I is true, II is false

I is true and II is also true

I and II are false

I is false, II is true

Question 2 of 10

Question 3 of 10

3. A three phase, 50 Hz induction motor has a full load speed of 1440 rpm. Speed of the stator field revolving rotor structure is?

145 rad/s

157 rad/s

150 rad/s

6.28 rad/s

Question 3 of 10

Question 4 of 10

4. Insertion of external resistance in the squirrel cage induction motor _________

does not affect

decreases torque

increases torque

increases torque for some seconds and then decreases

Question 4 of 10

Question 5 of 10

5. The rated current in induction motor for a three phase system is 100A. What can be the no load estimated current for the machine?

12 A

20 A

30 A

5 A

Question 5 of 10

Question 6 of 10

6. A 400, 3-phase, 50 Hz, 4 pole induction motor takes a line current of 10 A with 0.86 pf lagging. What is the stator input?

5.95 kW

4.45 kW

6.95 kW

8.38 kW

Question 6 of 10

Question 7 of 10

7. The rotor winding for 3-phase slip ring induction motor having delta connected stator must be connected in _________

any of the mentioned

star

tertiary

delta

Question 7 of 10

Question 8 of 10

8. In a three-phase induction motor, the starting torque is maximum when?

r2 = x2

r2 = 1 pu

r2 = 1/x2

r2 = (x2)²

Question 8 of 10

Question 9 of 10

9. If the rotor circuit resistance is increased in an induction motor, maximum torque will occur at _________

none of the mentioned

same speed

higher speed

lower speed

Question 9 of 10

Question 10 of 10

10. The direction of rmf when a single phase supply is given to stator of three phase induction motor is?

2Ns

-Ns

Zero

Question 10 of 10