A THREE-PHASE SQUIRREL CAGEINDUCTION MOTOR

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Three-phase induction motors construction consist of : The Stator The Rotor

The squirrel-cage and the wound-rotor induction motor have nearly the same stator construction and winding arrangement.

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The three-phase induction

motor

The squirrel-cage induction motor

The wound-rotor induction motor

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Mainly we discuss a three-phase squirrel cage induction motor.

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Squirrel cage construction, the rotor winding consists of a number of rotor bars, short-cut by rings from both side, see figure below.

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PARTS OF SQUIRREL-CAGE MOTOR

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TYPES OF SQUIRREL-CAGESplit phaseCapacitor startCapacitor start capacitor run

Permanent split phase capacitor run

Shaded pole

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CLASSIFICATION OF SQUIRREL CAGE INDUCTION MOTOR

It is classified six types.There are class A,

class B, class C, class D, class E and class F

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CLASS AStarting Torque :

NormalStarting Current :

NormalSlip :

NormalUses :

Fans, Pumps, Low inertia loads which are frequently started and stopped

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CLASS BStarting Torque :

NormalStarting Current :

LowSlip :

NormalUses :

Loads which has High Moment of inertia, large fans pumps.

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CLASS CStarting Torque :

HighStarting Current :

LowSlip :

NormalUses :

Crushers, boring mills, conveyors, textile machineries, wood working equipments.

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CLASS DStarting Torque :

HighStarting Current :

LowSlip :

HighUses :

Bulldozers, shearing machines, punch presses, hoists, foundry & stamping machines.

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CLASS EStarting Torque :

LowStarting Current :

NormalSlip :

Low

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CLASS FStarting Torque :

LowStarting Current :

LowSlip :

Normal

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Finally, We can discuss advantages & disadvantages of squirrel cage induction motor.

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ADVANTAGESNo commutator and brush.

Low weight, volume and cost.

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DISADVANTAGESRequires a complicated and costly power modulator and two stages of power conversion.

Control is more involved.Slow response.Drive is costly.

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