Losses in Induction motor


      The losses in an induction motor can be classified as

(i)  Constant losses and

(ii) Variable losses

Losses in Induction motor


Constant Losses :

             

     These can be further classified as iron and Mechanical losses.


Iron Losses :


     Iron or core losses occur in stator and rotor core.These include eddy current losses and hysteresis losses. The iron losses depends on the frequency. The rotor frequency is very small which is slip times the supply frequency. Hence the rotor iron losses are very small and may be neglected.


Mechanical Losses:

       

     These include frictional losses at the bearings and windage losses.



Variable Losses : 

      

     These include copper losses in stator and rotor winding due to current flowing in the winding. As current changes as load changes.These losses are said to variable losses.


Total rotor copper losses : 3 I22 R2  

Where  

   I2 = Rotor current / phase at a particular load and

   R2 = Rotor resistance / phase.



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