An induction electric motor operates in principle at a vacuum, close to the synchronous speed. In this type of motor, the rotating field is produced by the magnetization current and thus, the slip between the rotor and the magnetic fields is small, but the rotor frequency is also reduced.
The movement is small and in turn the induced voltage in the rotor rod and the flow of the current in the rotor also become small. Because the frequency of the rotor is much smaller, its reactance is close to zero and the rotor current will be almost in phase with the rotor voltage.
The rotor current produces a small magnetic field, with an angle greater than 90 °, behind the resulting magnetic field. It may be noted that the stator current will be large still unfilled, and should supply most of the resulting rotating field.
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For this reason electric induction motors have large unladen currents when compared to other types of motors.
As the magnetic field of the rotor is small, the induced torque must also be small, but large enough to oppose the losses of the motor. The induced torque keeps the motor spinning.