Understand The Working Principle Of AC Induction Motors

By Steven Harrisson, March 20, 2015

AC induction motor is one of the most commonly used electrical motors used for various purposes. It converts electrical energy into mechanical energy and it is known as asynchronous motor, because it runs at a synchronous speed. The most common type of induction motor is the three phase AC induction motor, since it requires no starting device and is very economical. If you want to understand the working principle of AC induction motors, read on.


The three phase AC induction motor is composed of two major parts: stator and rotor. The stator is made up from several slots, in order to construct a 3-phase winding circuit, connected to a 3-phase AC power source. The winding circuit is especially modified with its slots to produce a rotating magnetic field as soon as they get AC. The other major part of 3-phase AC induction motor is the rotor. It is composed of a cylindrical laminated core with parallel slots able to carry conductors. Most conductors are nothing more than heavy copper or aluminum bars, perfectly fitting in each slot and short-circuited by the end rings. The slots are not exactly made parallel to the axis of the motor’s shaft, but they are arranged in a manner to reduce the magnetic humming noise and avoid motor stalling.

With AC induction motors, it is not all about supplying. The working principle of all types of AC induction motors is unique in all terms, yet simple since there is induction process involved. When supplying energy to the stator winding, flux is being generated in the coil as a consequence of current flow. Then, the rotor winding becomes short circuited in the rotor and the flux from the stator cuts the coil in the rotor. And since it is short-circuited, current starts flowing in the rotor’s coil. With the current flowing, flux is being generated in the rotor, which means, there are two flux now: stator flux and rotor flux. Due to this, the rotor deals with a torque that forces it to rotate in the direction of the magnetic fix’s rotation.

AC induction motors and their working principle bring many advantages. These are self-starting motors, more economical, easier to maintain and are more rugged compared to other motor alternatives. However, the greatest advantage of AC induction motors is their sheer simplicity. With only one moving part, these motors are incredibly cost-effective, quiet and durable.