To generate electricity, three things are necessary, which are motion, a magnet, and wire coil. In the case of a motor, the stator is the coil of wire that surrounds a rotor to generate electric power. It is a part of a motor that creates a magnetic field to create direct current (DC) to charge the motor. A stator coil is the static part of a motor and generates a rotating magnetic field. It is made up of the core, frame, and winding, with the core being the portion of the stator that supports and protects the three-phase winding. The magnetic field produced by a stator coil causes the rotor, in an electric motor, to turn. An electromagnetic field (EMF) is produced by the interaction of the rotor and stator.
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Applications of Stator Coils
The concept of a stator is used in a wide variety of motors from the fan on a computer to giant turbines that produce electric power. The most common use of stators is in lawn mowers, automobiles, and simple electric motors. Engineers depend on stator coils when designing motors since they are a consistent and reliable source of electric power.
Materials Commonly Used in Manufacturing Stator Coils
The majority of stators are made from copper and iron housed in a casing of aluminum or steel. The iron in the construction is an efficient material for the generation of electric flux, a measure of the strength of an electric field. As with many electrical devices, copper wire is used for its conductivity, ductility, and high melting point. The copper wire winding of the stator is lacquered, or laminated, to increase the density of the winding.
Stator Coil Design and Function
In a motor for a vehicle, the stator is part of the alternator, which produces alternating current (AC) to keep an engine running and is required to produce extra current that can be stored in the battery. Since the battery only stores DC current, a regulator converts the AC current to DC for battery storage. The essential function of the stator is to ensure that the rotor keeps turning to produce enough power. When the rotor is spinning, a commutator keeps the magnetic field correctly aligned. As the current increases, the commutator becomes larger and more forceful. A stator can be either a permanent magnet or electromagnet. In cases where the stator is an electromagnet, it is known as a field coil or field winding.
A key factor in wire winding is the fill factor, which needs to be kept high to ensure the efficiency of the electric field that the stator produces. Insulation, lamination, and winding has to be completed in the most efficient manner to increase the fill factor. In the typical three phase motor, there are six slots with three pairs of coil windings that are offset by 120o.
The goal of manufacturers is to maximize the amount of copper wire in the slot fill to increase the torque output. This challenge makes the production of stators difficult since engineers have to determine how much slot fill is necessary for an application.