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 INDUCTION

 MOTOR

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 An induction motor works on

transforming action.

The stator works as the primary while

the rotor works as the secondary.

 It is also called asynchronous motor.

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It consists of two parts:

1. Stator  - It is the stationary part of themotor.

2. Rotor - It is the rotating part of themotor.

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Stator Stamping

Tootho s

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CORE

WINDINGS

SLOTS

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  Stator has three main parts:

Outer Frame – It is the outer body of theof the motor.It protects the inner part of the machine.

   Stator Core – Built up of high gradesilicon steel.

Carries the alternating magnetic field.

   Stator winding  – as a three phasewinding.

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!here are two types of rotors which are

employed in " – phase induction motor.

 

 Squirrel Cage Rotor.

 

 Phase Wound Sli! Ring Rotor.

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It consists of a laminated cylindrical coreha#ing semi closed circular slots at the outer periphery. Copper or aluminum bar conductors are placed

in these slots and short circuited at each end

 by copper or aluminum rings called shortcircuiting rings.

!he rotor winding is permanently short

circuited and it is not possible to add anye$ternal resistance.

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!he rotor slots are not parallel to the shaft buts%ewed to –

 &educe humming .

'ro#ide smoother tor(ue for different positions ofrotor.

&educe magnetic loc%ing of stator and rotor.

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It is also called S"IP RIN# ROTOR

Consists of a laminated core ha#ing semi closed slotsat the outer periphery and carries a "-phase insulatedwinding.

!he rotor is wound for the same number of poles asthat of stator.

!he three finish terminals are connected together

forming a star point and the three star terminals areconnected to three slip rings fi$ed on the shaft.

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 Prin$i!le o% O!eration) rotating field is set up in the stator when a "- 'hase

supply is gi#en.

!he stationary rotor cut the re#ol#ing field and due toelectromagnetic induction an e.m.f . is induced in the rotor

conductor.

)s the rotor conductor is short circuited current flowsthrough them.

It becomes a current carrying conductor in magnetic field

and start rotating.

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 Sli!

Induction motor rotor always rotate at a speed less thansynchronous speed.

!he difference between the flu$ *+s, and the rotor speed *+,

is called slip.

  Slip *+s – +, × 1//

  +

Slip speed +s – +

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