Induction Motor

Induction motor Main parts are Stator Rotor

Stator Frame: used as mechanical protection and support for the winding made of cast iron Insulated copper wire with varnish:- the wires are fitted in the slots of; Insulated slotted lamination, which are made from high grade alloy of steel to reduce eddy current loss.

Rotor It is the rotating part of the motor Depending on the rotor structure there are two types of rotors : Squirreled- cage rotor and Slip- ring rotor

Squirrel cage It consists of a cylindrical laminated core with parallel slots for carrying the conductors, which are heavy bars of copper or aluminum. Used to reduce eddy current loss The copper bars are short circuited by end rings at both end.

Other parts of induction machine Shaft and Bearing Shaft : is placed inside the rotor so when rotor rotates then the shaft rotate with it. Bearings : is used to mount the rotor to reduce friction on both side

Cont.. Fan – are used for adequate circulation of cooling air securely keyed on the rotor shaft. Terminal box: is used for holding stator and rotor winding ends. Two end covers: with suitable bearings provide support for the rotor assembly.

Principle of Operation of Three Phase Induction Motor When a three phase source is connected to an induction motor the rotor stats to rotate. What makes the rotor to rotate?

When a three phase supply is connected to the three phase winding of the stator field winding it produce three independent magnetic flux. The resultant of this magnetic flux is called net flux The magnitude of the net flux remain constant but the position keeps on changing in circular manner. Which in turn produce a relative motion between the rotating magnetic field and the rotor. When this varying magnetic flux cuts through the rotor conductor current is produced and start to circulate in the rotor conductor.(Faraday’s law)

so the current carrying rotor under the rotating magnetic field will start to experience a force.(Lorenz's law ) And the direction of the force is given by the right hand rule. In summery Three phase induction motor works of the principle of electro magnetic induction where the relative motion between the flux and the rotor, caused by the rotating magnetic field induces a current in the rotor, forcing it to rotate in the same direction.