3 phase induction motors

3-Phase Induction Motors

Motor : A motor is an electical device which converts electrical energy to mechanical energy

Induction : Induction is the word comes out from the induce,For example if your neighber eating sweets you may feel sweetnes which means indirect effect.

Induction Motors : Induction Motor is a motor which works on the principle of induction

3-Phase Induction Motors : Runs on 3 phase AC supply.

Induction Motor Components

A 3-phase induction motor has two main parts:

• A stator – This is the sationary part of the motor
consisting of a steel frame that supports a hollow,cylindrical core of stacked laminations. Slots on the internal circumference of the stator house the stator winding.

• A rotor – The meaning of rotor itself says that this is the rotating part of the motor which is composed of punched laminations, with rotor slots for the rotor winding.

Types of 3 phase induction motors :

There are 2 types of 3 phase induction motors based on the rotor windings

Squirrel-cage induction motor :

In this motor the rotor looks like a sqirrel cage that's why the name squirrel cage induction motor. Squirrel cage rotor consists of thick copper bars, which are slightly longer than the rotor,which are pushed into the slots.

Induction Motor Components The ends are welded to copper end rings, so that all the bars are short
Circuited. In small motors, the bars and end-rings are diecast in aluminium to form an integral block.

Slip ring induction motor (wound-rotor induction motor)

In this the rotor will be having Conventional 3-phase windings made of insulated wire, which produce a wound-rotor.A wound rotor has a 3-phase winding, similar to the stator winding.

The rotor winding terminals are connected to three slip rings which turn with the rotor. The slip rings/brushes allow external resistors to be connected in series with the winding.

The external resistors are mainly used during start-up,under normal running conditions the windings shortcircuited externally.

Induction Motor: Operating principle : Operation of 3-phase induction motors is based upon the application of Faraday's Law of electro magnetic induction.

Advantages of 3 phase induction motors

• 3-phase induction motors are simple, rugged, lowcost, and easy to maintain.
• They run at essentially constant speed from zero-to-full load.
• Therefore, they are the motors most frequently encountered in industry.


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