how to select AC contactor rating for STAR-DELTA, induction motor 5.5 kw to 55 kw

 

The motor full load current divided by 1.732 is the full load current through the contactors. This is the contactor minimum rating. Choose the next higher size if you are at the border of the selection range.
Also look for ratings under AC3 (inductive motor load).
Best regards.
Sekar

 

The WYE-DELTA 3 phase motor can be dual voltage, dual speed or start WYE run DELTA. With WYE-DELTA start/run the motor has 33% full torque and draws 33% normal starting current. The motor has about 746 watts per horsepower minus all losses. 5.5 kw is about 7 hp and 55 kw is about 75 hp etc. NEMA motor starters and contactors for 3 phase for a nominal 480 volts are rated as follows: size 1 through 10 hp, size 2 is 25 hp, size 3 for 75 hp.

 

Reponding to Rajkumar's query:

Can you provide country of installation, i.e., USA, Canada, European, etc? Also, any special duty, eg, mining, marine, etc.

Regards,
Phil Corso, PE
(Boca Raton, FL)