Virtual lab

Blocked-Rotor Test

1) In a 3 phase wound rotor induction motor, 3 phase balanced supply is given to the rotor and the stator winding is short circuited. The rotor would:

Not run

Run in the direction of the rotating field

Run against the direction of rotating field

Run at half the synchronous speed

2) A three phase, 50Hz, 4 pole squirrel cage induction motor has its stator rewound for 6 poles without any alterations in the rotor. The motor would now run at a speed:

<1000 rpm

<1500 rpm

<3000 rpm

<0 rpm

3) A three phase induction motor is running at a slip s. If its two supply leads are interchanged, then its slip at that instant is equal to :

1-s

2-s

1+s

4) The stator of a 3 phase 6 pole wound rotor induction motor is connected to a 50Hz source but its rotor is energized from a 20Hz source. The rotor would run at a speed of

1600 rpm

600 rpm

1000 rpm

400 rpm

5) The maximum torque produced (Tem) produced by a three phase induction motor:

Increases as the stator resistance increases

Decreases as the stator resistance increases

Decreases as the stator resistance decreases

Is unaffected by change in stator resistance

Shakshat Virtual Lab

INDIAN INSTITUTE OF TECHNOLOGY GUWAHATI