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The Basics of Electric Motor

Electric motors use alternating current (AC) or direct current (DC) to convert electrical energy into mechanical power. They are found in many different applications, from household appliances to automobiles and trains.

Working Principle
The working principle of an electric motor is based on Faraday’s Law of Induction, which states that when an alternating current interacts with a changing magnetic field, a force is generated. The stator of the motor contains a sequence of steel alloy laminations that are wound with wires to make induction coils, one for each power source phase.

Several of these coils are connected to make a circuit which rotates a part of the motor shaft called the rotor. The rotor is then enclosed within a casing with end caps that contain bearing mountings. The casing also often has a fan that draws in ambient air to cool the rotor and motor parts.

Induction Motors
Induction motors are the most common type of electric motor. They have a ferromagnetic core with a magnetic field that is induced by supplying an alternating current in windings.

They come in both salient and non-salient-pole configurations. In salient-pole motors, the poles of the ferromagnetic core face one another and each winding is wound around a specific pole. This creates a south or north pole of the magnetic field as current moves through the winding.

Non-salient-pole motors, on the other hand, have a cylinder with wound wire distributed equally in slots around the circumference of the cylinder. When a current passes through the wound wire, it forms the poles of the magnetic field and the cylinder spins continuously.