Basics of AC Electric Motors

What is An Induction Motor?

An induction motor is a type of alternating current motor where power is supplied to the rotor by means of electromagnetic induction.

An electric motor converts electrical power to mechanical power in its rotor (rotating part). There are several ways to supply power to the rotor. In a DC motor this power is supplied to the armature directly from a DC source, while in an induction motor this power is induced in the rotating device. An induction motor is sometimes called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. The primary side's currents evokes a magnetic field which interacts with the secondary side's emf to produce a resultant torque, henceforth serving the purpose of producing mechanical energy. Induction motors are widely used, especially polyphase induction motors, which are frequently used in industrial drives.

Induction motors are now the preferred choice for industrial motors due to their rugged construction, absence of brushes (which are required in most DC motors) and — thanks to modern power electronics — the ability to control the speed of the motor.

Types of Induction Motor?

Induction Motors are classified based on the type of rotor used. They are

1. Squirrel Cage Induction Motors &

2. Slip-Ring or Wound-Rotor Induction Motors

What is A Squirrel Cage Induction Motor ?

The reason for the name “Squirrel cage” is because of the type of rotor used in these motors. Almost 95% of the induction motors used is of squirrel cage type.