03/02/2018

Compare Squirrel Cage Induction Motor and Slip Ring Induction Motor


Parameters
Squirrel Cage Induction Motor
Slip Ring Induction Motor
Rotor
Copper bars are slotted in the rotor and these bars are short circuited from both ends by end rings
Three phase winding is slotted in the rotor similar to stator winding

End rings
Two end rings are used on both side of rotor
End rings are not used
External Resistance
As the rotor is short circuited by end rings, extra resistances are not connected.

External resistance can be added from rotor side
Slip rings and brushes
Not used
Three slip rings and brushes are used as per current capacity at rotor side
Starting torque
Moderate starting torque. The starting torque cannot be increased.

High starting torque is achieved by adding external resistances to rotor side.

Speed control
Speed control from rotor side is not possible because the rotor itself a closed by end rings.

Speed control is possible from stator and rotor side. The speed control from rotor side is done by rotor resistance starter.
Copper losses
Better space factor for rotor slots, shorted over hang and smaller copper loss

Large over hang resulting higher copper loss
Cooling condition
Cooling condition is better because it has bare end rings thus large space available for fan

Cooling condition is affected by some times sparking between slip rings and brushes
Overload capacity
Better overload capacity

Low overload capacity as compared to squirrel cage induction motor

Power factor
Better power factor due to smaller rotor overhang

Comparatively high power factor
Pull out torque

High
Low

Maintenance
Low
High
Construction
Simple and robust

Complicated
Cost
Low
High
Efficiency
High
Low as compared to Squirrel cage Induction Motor
Applications
Fan, printing machine, lathes, drill machine, blower etc

Lift, compressor, crane, hoist etc.


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