Main Interruptor for MCC

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voyager2

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I have to buy a main circuit breaker (CB) for a 480 V Motor Control Center (MCC). Which should be the rated current of the CB. It is simply the sum of the rated currents of the eleven motors it has ? Or should I apply a security correction factor. The MCC has two 3 HP motors, one 10 HP motor, one 15 HP motor, one 20 HP motor, one 40 HP motor, two 75 HP motors and three 100 HP motors. Should I consider the starting current of the greater motor ?

[ June 23, 2005, 02:24 PM: Message edited by: voyager2 ]
 
Re: Main Interruptor for MCC

I assume that the MCC is existing and as such the MCC horizontal bus has been sized for the motor loads to be served. If so then size the main breaker to protect the MCC bus.
 
Re: Main Interruptor for MCC

Another approach might be to size the OCPD as a motor feeder OCPD per 430.62.
 
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