Electrical Machines Questions and Answers – Induction Machines
Induction Motor Phasor Diagram
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If the operating voltage of the induction motor is increased by twice while keeping the frequency of the operation constant.
Then the new starting torque will be
Then the new starting torque will be
Correct!
Wrong!

If the frequency is reduced by 50% for a 3phase, 50 Hz induction motor having 4 poles. The slip at which the maximum torque occurs becomes
Correct!
Wrong!

If the voltage and frequency of the induction machine is reduced to 50% of the operating region,the slip of the machine will be
Correct!
Wrong!

The rotor of the slip ring induction motor is connected to an ac source and stator is short circuited. If the rotating magnetic field is rotates clockwise, the rotor rotates in
Correct!
Wrong!

The torque and the slip characteristic is most correctly related by which of the following below in the region of 3050% operation of slip.
Correct!
Wrong!

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

A 3phase induction motor had the maximum rated torque of 40 Nm while the load torque applied to it is 55 Nm.
Correct!
Wrong!

The phasor diagram for the induction generator is best represented by
Correct!
Wrong!

If the voltage of a three phase induction motor if increased to 200%, then the slip if the machine changes to
Correct!
Wrong!

I. Maximum torque can be achieved by inserting an additional resistance at desired slip in the rotor.
II. Maximum torque can be altered by adding the external resistance in the rotor.
II. Maximum torque can be altered by adding the external resistance in the rotor.
Correct!
Wrong!

The power input to the 3phase induction motor is 60 kW. The stator losses total 1 kW. Find the mechanical power developed at the slip of 3%.
Correct!
Wrong!

Approximately the efficiency of the rotor of the induction motor depends on the
Correct!
Wrong!

The phasor diagram for the induction motor is
Correct!
Wrong!

Rotor leakage impedance at starting is different from its value at normal running conditions.
Correct!
Wrong!

Choose the most appropriate. The torque slip characteristic of the induction motor at the slip of 36 %.
Correct!
Wrong!

An induction motor X operating at the slip of 3%.
An induction motor Y operating at slip of 40%.
An induction motor Y operating at slip of 40%.
Correct!
Wrong!

If the hysteresis is neglected in the induction machine, then the the air gap flux _______ the resultant mmf.
Correct!
Wrong!

On increasing the starting torque of the induction motor, the maximum torque is also increased.
Correct!
Wrong!
