Slip Ring Motor Protection

[Manmohan]

We are using slip ring motors for cranes applications ( 100 HP / 415 V). We have used proper rating over load relays for protection of motors against over loads. Inspite of this rotor of motor got short-circuited / earthed and over load would not trip.

 

As per me if there is any over-load on motor it should be reflected in stator winding and o/load should trip.

 

What could be the suitable protection to avoid this type of failure.

[marke]

Hi

 

If the rotor developes a short while the motor is running, it will not change the stator curent as it will be shorted anyway.

If you try to start the motor with a shorted rotor, it will draw serious overcurrent and the overload will trip.

 

I am not aware of a good rotor protection system.

[RKParida]

We are using slip ring motors for cranes applications ( 100 HP / 415 V). We have used proper rating over load relays for protection of motors against over loads. Inspite of this rotor of motor got short-circuited / earthed and over load would not trip.

 

As per me if there is any over-load on motor it should be reflected in stator winding and o/load should trip.

 

What could be the suitable protection to avoid this type of failure.

 

 

Dear Mohan,

 

U can use Electronics overload relay in the rotor circuit,

 

BOCR relay BCH make.

 

Regards,