Dose the code address a part start (50/50) motor OCP directly, if so I missed it.
Here is why I ask.
450 hp compressor motor.
485 FLA (Name Plate FLA)
Part start, starts under no load.
Should the OCP be 250% max for half the FLA (242.5) which would be 606.25 amp or 600 amp breaker. I think this is the case for two speed motors but not sure about part start motors.
FD3030
By OCP I assume you are referring to the OCPD, i.e. a circuit breaker or fuses, not the Over Load Relays. In
motor circuits you have to differentiate and I find it helpful to call them SCPD (Short Circuit Protection Device) and OLR (Over Load Relay), it keeps things more clear.
Here is the way it works. Part Winding is not specific as to that percentage, there are 2/3 - 1/3, 3/5 - 2/5, and 1/2 - 1/2 versions, but in this case you apparently already know which one you have. Technically you have to consider each set of windings as if it is a separate motor that is the size of the percentage of the whole represented by the winding configuration because each set of windings must have it's own appropriately sized SCPD. But in most cases because each has its own separate OL device for running over current protection, the sizing rules of the
SCPD can allow one device to be adequate for each of the windings individually; the SCPD is only required to be the Short Circuit protection. So the NEC doesn't bother with making a distinction on the SCPD for PW motors, as long as you have 2 sets of OL relays; one for each winding. You size the SCPD according to the motor FLC or nameplate FLA as per normal. In your case I think the FLA is higher than the NEC table for FLC, so you use that value (I don't have my NEC on this PC) and apply table 430.52 according to the type of SCPD you are going to use.
If you were to attempt to use only fuses as the entire circuit protection (no separate OL relays, a bad idea), then you would have to have 2 separate OCPDs sized for each set of windings.
In IEC countries you often see breakers with ADJUSTABLE thermal trips, essentially what we might consider manual motor starters, ahead of the contactors and in that case since each one is providing individual OL protection it is also providing individual SC protection. I happen to think that in the case of something as large as 400HP that would likely cost more than one larger SCPD and 2 OLRs.
