3 February 2018

Compare Squirrel Cage Induction Motor and Slip Ring Induction Motor

Squirrel Cage Induction Motor
Rotor
  • Copper bars are slotted in the rotor and these bars are short circuited from both ends by end rings.

End rings
  • Two end rings are used on both side of rotor

External Resistance
  • As the rotor is short circuited by end rings, extra resistances are not connected.

Slip rings and brushes
  • Not used

Starting torque

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

Copper losses
  • Better space factor for rotor slots, shorted over hang and smaller copper loss

Cooling condition
  • Cooling condition is better because it has bare end rings thus large space available for fan

Overload capacity
  • Better overload capacity

Power factor

Pull out torque
  • High

Maintenance
  • Less

Construction
  • Simple and robust

Cost
  • Low

Efficiency
  • High

Application
  • Fan, printing machine, lathes, drill machine, blower etc 

Slip ring Induction Motor
Rotor
  •  Three phase winding is slotted in the rotor similar to stator winding.

End rings
  • End rings are not used.

External Resistance
  • External resistance can be added from rotor side

Slip rings and brushes
  • Three slip rings and brushes are used as per current capacity at rotor side

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

Speed control
  •  Speed control is possible by rotor resistance starter

Copper losses

Cooling condition
  • Cooling condition is affected by some times sparking between slip rings and brushes.

Overload capacity
  • Low overload capacity as compared to squirrel cage induction motor

Power factor

Pull out torque
  • Low

Maintenance
  • High

Construction
  • Complicated

Cost
  • High

Efficiency
  • Low as compared to Squirrel cage Induction Motor

Application
  • Lift, compressor, crane, hoist etc.


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