3 phase Induction Motor

While operating on variable frequency supplies, the AC motor requires variable voltage in order to

• protect the insulation.

• avoid effect of saturation.

• improve the capabilities of the inverter.

• protect thyristor from dV / dt.

A 2-pole, 3-phase, ______ Hz induction motor is operating at a speed of 550 rpm. The frequency of the rotor current of the motor in Hz is 2.

• 9.37

• 9.12

The concept of V/f control of inverters driving induction motors results in

• constant torque operation

• speed reversal

• reduced magnetic loss

• hormonic elimination

Stator voltage control for the speed control of induction motor is suitable for

• Fan and Pump Drive

• Drive of a crane

• Running as the generator

• Constant Load drive

Objective of Rotor resistance starter is...

• To limit the starting current

• To control the starting torque

• To vary the speed

• All the above

A wound rotor induction motor is preferred over squirrel cage induction motor when the major consideration involved is

• High starting Torque

• Low starting current

• Speed control over the limited range

• All of the above

Wound rotor and squirrel-cage motors with the high slip which develop maximum torque at standstill are used for

• Presses and Punches

• Machine tools

• Elevators

• All of the above

V/f is maintained constant in the following case of speed control of induction motor:

• Below base speed with voltage control

• Below the base speed with frequency control

• Above base speed with frequency control

• None of these

Name the type of induction motor which produces high starting torque

• Slip ring Induction motor

• Squirrel cage induction motor

Slip ring induction motor controlled by

• Rotor resistance starter

• Solid state rotor resistance starter

• both a & b