400 vs. 350 Amps Circuit Breaker 2

[BGD011]

We do have a 200Hp/460V/3ph/60Hz motor. The NEC tells me that the size of the circuit breaker (CB) should be 350 Amps. If we use a 400 Amps CB, is it violation of the NEC?
FLA of this motor is 240 Amps.

Thank you indeed in advance!

 

[rbulsara]

Which part of NEC tells you that? Is this a VFD?
NEC would allow up to 250% of the FLA rated CB. Look up Table 430.52 in NEC 430.

 

[BGD011]

Thank you Rbulsara!

I see it now at that 2005 NEC table 430.52 last column.
The motor is not on the VFD but there is an auto transformer starter. I was not sure what it is the maximum rating for these CB’s,... Thanks again!

 

[JBUDA54]

The Project I am working on; we are using a 400A Thermal-Magnetic (Inverse time) circuit breaker as stated in the Table 430.52 far column. According to the code we could use 2.5 *240FLA = 600A but we have chosen a 400A with a trip setting of 7.5X or 3000A which is 12.5 X FLA. The Motor Short Circuit Protector NEC Reference 430.52 (7) can have a trip setting of no more than 1700% FLA for high efficiency motors which we chose 1250% for the energy efficient motor loads. The Motor Overloads will protect the motor and cable in the event of a overload condition. We are using a 3/C 350 kcmil cable which is good for 310A at 75 deg C according to Table 310.16. This exceeds the 1.25 * (240)FLA = 300A that is required per the continuos Duty requirement 430.22 (a).

 

[BGD011]

Thank you JBUDA54!
It is helpful information.