Induction Motor Quiz

For starting of an induction motor, star/delta starting can be considered equivalent to an autotransformer starter with the ratio of

• 0.333

• 0.5

• 1

• 0.577

A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor current will be

• 50 Hz

• 25 Hz

• 5 Hz

• 2 Hz

The resultant flux in an induction motor is equal to the

• Maximum value of flux due to any phase

• Twice of the maximum value of flux due to any phase

• 0.5 times the maximum value of flux due to any phase

• 1.5 times the maximum value of flux due to any phase

The frequency of rotor current in an induction motor is

• slip times the frequency of stator current

• slip times the frequency of supply

• One by slip times the frequency of stator current

• One by slip times the frequency of supply

Slip of an induction motor increases with

• increase in current and decrease in torque

• increase in current and torque

• decrease in current and torque

• decrease in current and increase in torque

For a 4-pole, 50 Hz induction motor has starting current as 5 times to that of the full load current working at a speed of 1450rpm.The ratio of starting to full load torque will be

• 0.83

• 0.17

• 0.67

• 1

Starting methods applicable to both squirrel-cage and slip ring induction motors is/are A. DOL starting B. Auto transformer starting C. Rotor resistance starting

• A, B

• A, B, C

• B, C

• A, C

The method which employs reduction of the voltage while induction motor starting is/are A. DOL starting B. Auto transformer starting

• Only A

• A, B

• Only B

• Neither A nor B

A 3-phase, 4-pole, 50 Hz induction motor is uses DOL method of starting. It is later replaced by reactance method of starting with a fraction of 'x', then the starting current reduces by

• x

• x^2

• 1/x

• x^3

Which starter cannot be used for squirrel cage induction motor

• star delta

• autotransfomer

• dol starter

• rotor resistance starter