Electric Motor - Terminology

Terminology

In an electric motor the moving part is called the rotor and the stationary part is called the stator. Magnetic fields are produced on poles, and these can be salient poles where they are driven by windings of electrical wire. A shaded-pole motor has a winding around part of the pole that delays the phase of the magnetic field for that pole.

A commutator switches the current flow to the rotor windings depending on the rotor angle.

A DC motor is powered by direct current, although there is almost always an internal mechanism (such as a commutator) converting DC to AC for part of the motor. An AC motor is supplied with alternating current, often avoiding the need for a commutator. A synchronous motor is an AC motor that runs at a speed fixed to a fraction of the power supply frequency, and an asynchronous motor is an AC motor, usually an induction motor, whose speed slows with increasing torque to slightly less than synchronous speed. Universal motors can run on either AC or DC, though the maximum frequency of the AC supply may be limited.