Operating Principle - Electrolux EWX11831 Service Manual

13.10.2 Operating principle

The alternating current permanent magnets motor is a synchronous electric motor: the speed of rotation when
stationary only depends on the frequency of power supply and it is independent of the load (torque at the axis).
Like all electric motors, the permanent magnets motor consists of a stator and a rotor: both these components
contribute to the production of torque by iteration between the respective magnetic fields.
The magnetic field of the stator is produced, as in asynchronous motors, by the current that passes through the
windings; if this current is three-phase alternating current, the magnetic field of the stator has a fixed intensity
and variable direction (rotating): hence a rotating magnetic field is produced. The speed of rotation of the
rotating magnetic field is proportional to the frequency and inversely proportional to the number of poles.
The magnetic field of the rotor is generated by the permanent magnets which are positioned in the rotor.
When current passes through the stator windings, these generate a magnetic field that tends to attract the
magnets (the north poles of the stator attract the south poles of the rotor, and the south poles attract the north
poles); since the magnetic field of the stator is rotating, the rotor (which is magnetised) tends to follow it, thereby
causing the rotation of the rotor itself.
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