Magnetic Stator Assembly
A magnetic stator is the stationary part of a motor. It consists of ferromagnetic metal and provides the magnetic field which interacts with polarization in the windings to produce torque.
A stator must perform two functions:
– Magnetically, it must create a fixed magnetic pole face for each winding so that when current flows through the winding it magnetizes according to Fleming’s left-hand rule (see below). This by itself would tend to make all poles point in one direction, but by either adding or subtracting magnets (and hence poles) we can arrange it so that alternating currents – if applied at exactly twice the frequency of rotation – produce no net effect on the rotor; this arrangement is known as an “isolation transformer”.
– Statically, it must not be subject to forces caused by the motion of the rotor. This means that all magnetic pole faces are stationary with respect to the air gap (or they would produce eddy currents). It also means that there is a definite air gap between each magnet and each flux carrying path. A combined stator/air gap assembly is referred to as a “stator core arrangement.”