[Physics Class Notes] on Types of AC Motors Pdf for Exam

A.C. motors are induction motors. The air A.C. motor is a motor that transforms alternating current into mechanical energy. 

Working Principles, Construction, Classification, and Types

Working Principles

Induction motors operate on the theory that when a closed conductor is placed in a magnetic field, it produces torque, or on the combined action of electromagnetic induction and the motor principle.

Construction

The three-phase induction motor is made up of two parts:

Stator

It is built out of a steel frame that surrounds a hollow, cylindrical cone made up of thin silicon steel laminations to minimize eddy current and hysteresis loss. On the inner periphery of the core, a huge number of similar slots are carved.

The stator conductors are inserted into these slots, which are isolated both from one another and from the slots themselves. A balanced star or delta winding is used to link the conductors. Depending on the speed requirement, the windings are wound for a specific number of poles.

When high speed is required, the winding is wound with fewer poles and vice versa.

Rotor

Any mechanical load can be linked to the rotor, which is positioned on the motor’s shaft. There are 2 types of rotors:

A squirrel-cage rotor’s core is a cylindrical laminated core. It also has parallel slots for rotor conductors. Heavy copper or aluminum bars serve as the rotor’s conductors. Each slot receives one bar.

The rotor is made of laminated materials. The cylindrical core features uniform slots in which three-phase star-connected winding is installed. The open ends of the star winding are connected to three insulated slip rings installed on the motor shaft, which are coupled to carbon brushes.

Types

The different types of AC motors are: