The short-circuit rotor

Usually the induction electric motor with squirrel cage type rotor consists of two parts, the stator and the rotor.

In the stator the magnetic circuit of the electric motor, as a rule of the slotted type, where the coils are installed which, by appropriate connection, produce the rotating magnetic field. Already in the rotor the winding formed by copper or aluminum bars short circuited at the ends. The current in the rotor circuit is induced by the action of the rotating field of the stator.

This functioning motor in the magnetic field formed in the rotor circuit will chase the rotating field of the stator. It is impossible for the rotor of an induction motor to rotate at the same speed as the magnetic field. When the motor is energized, it will act as a transformer with the secondary being shorted, so it requires a much higher current than the rated current from the mains, which can reach about eight times its value. The high starting currents cause inconveniences, and it requires dimensioning cables with diameters much larger than necessary. In addition, there are short drops in the power factor, which is monitored by the utility, causing an increase in energy bills.

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