Q. During no load test of a 3 phase induction motor, the power drawn by the motor is to meet
Solution:
- No load test is performed when rotor rotates with synchronous speed and there is no load torque. This test is similar to the open circuit test on transformer.
- Actually, to achieve synchronous speed in an induction motor is impossible. The speed is assumed to be synchronized. The synchronous speed can be achieved by taking slip = 0 which creates infinite impedance in the rotor branch.
- During the no load test the energy consumed will be used to meet the core losses and the friction and windage losses.
- Rotor copper loss at no load is very less that its value is negligible.
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The diagram shows how the energy supplied to the motor is utilized and different losses in the motor.
- Power input = core loss ?? copper loss windage and friction loss
- Core loss occur only in stator, because at no load slip is very small , so frequency of induced emf in rotor will be extremely small.
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