The stator is the fixed part of an electrical machine that. Together with the rotor, it is a fundamental element to transmit electric current (in the case of electric generators) or power in the case of electric motors.
By electric machine we mean both electric motors and electric generators. The moving part of an electric motor is called a rotor. In the case of generators, the stator is the fixed part of the alternator that converts the mechanical energy of the rotor into electrical energy.
In alternating current machines, the stator is generally in the shape of a cylindrical tube with a certain wall thickness. The grooves where the stator coils are housed are made of stacked crowns of magnetic sheet with teeth in their inner circle.
In DC machines the stator is made up of a solid steel cylindrical frame. This frame has the poles or pole pieces fixed inside it with the corresponding coils.
Depending on the configuration it can be:
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Direct current: interacts with the movable armature to produce motor torque on the machine shaft.
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Alternating current: interacts with the rotating field to produce motor torque. In this case it is formed by a hollow structure made of stacked magnetic steel sheets.
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Alternating current (alternators) or direct current (generators). In this case, the stator interacts with the rotor and produces an electric current.
What is the function of the stator?
The stator has the function of supporting, at least partially, the machine. If it is a fluid-action motor machine, the stator also has the function of making all the expansion take place inside it, in electrical machines it is part of the magnetic circuit together with the rotor and contains the induced windings or inductors. .
In the case of an electric motor, the stator can act like a magnet (through the electromagnet effect), reacting with the armature to produce movement. When an electric current flows through the coils, a magnetic field is generated that interacts with the rotor. Today's electric motors place the field coil on the stator.
If it is an electric alternator, the stator can also act as an armature by accepting inductors from a moving field coil located on a rotor. In power generation or motion reaction coil is placed on the rotor.