Electric motor basics
An electric motor is a commonly used device that transforms electrical energy into mechanical energy through the interaction of magnetic fields. The main two components of an electric motor are the stator and rotor.
The stator contains copper windings which are designed to carry direct current and set up a magnetic field. The windings are alternately magnetized, creating a magnetic field in the stator. The rotor is levitated to one side by the magnetic field. Because the three windings are alternately magnetized, the rotor begins to rotate.
The magnetic field of the stator always rotates faster than the rotor (hence asynchronous electric motor). The speed difference between the magnetic field in the stator and the rotor is called slip. Because of this slip, a voltage is generated in the rotor in the rotor anchors, which are shorted, thereby creating a rotor current. The rotor current then creates a magnetic field in the opposite direction, also known as the counter EMF. Together, the magnetic field in the stator and the magnetic field in the rotor produce the torque that is delivered by the electric motor. Higher shaft load provides more slip, more slip generates more rotor current, more rotor current produces more counter EMF and thus more torque. This is typical of asynchronous short-circuit electric motors.