9.3 AC motor general description and principles of operation
9.3.1 General description of an AC motor
An AC motor has two main parts: a stator, which is fixed, and a rotor, which rotates with
the shaft.
The stator is the stationary part of the motor. Within the stator assembly there is an iron
core constructed from thin iron sheets coated with insulation. Copper wire, which forms the
phase windings, is placed in the slots of the iron core.
The rotor is the moving part in the motor. The rotor core is made of a stack of sheet-steel
laminations. Aluminum, copper or bronze conductors are placed in slots around the outer
periphery of the rotor core, and these conductors are shorted together by circular end rings
at each end of the rotor.
A speed sensor and a thermal sensor are enclosed in the motor too.
9.3.2 Principle of operation
Figure 10 shows a two-pole AC motor supplied by a three-phase current.
PRELIMINARY VERSION 51
Figure 10: Stator currents and flux in a two-pole AC motor.
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