Induced Electromotive Force

The coiled rotor induction electric motor can be used as a frequency conversion device when its rotor is driven at a given speed and the electromotive force is withdrawn through the collector rings. The determination of the direction of the induced electromotive force can be made through the rule of Fleming of the right hand, that is, at rest, the frequency of the electromotive force induced in the rotor is equal to the frequency of the rotating magnetic field. But if the rotor were able to rotate at the same speed as the rotating magnetic field, there would be no induced voltage. Thus the frequency of the induced voltages in the rotor varies 174654.00 inversely with the rotor speed, from a maximum with the rotor at rest, to the zero frequency at the synchronous speed.

Thus we can imagine a squirrel-cage induction motor with rotor composed of copper conductors embedded in a three-conductor rotor iron core (A, B and C) and its relation to a multipolar magnetic field caused by a three-phase winding , due to the rotating field has a magnetic flux rotating at the synchronous speed clockwise relative to the rotor conductor A.