I have a 3 phase system that requires the use of numerous 3 phase and 1 single phase device therefore a neutral is required on the system. That said the system is being supplied through a slip ring. My question is if the main 3 phase load needs to accomodate 80A does the Neutral need to be sized the same or can it be smaller as there is only a requirement for a 1 off single phase supply using one of the 3 phases of 4amps?

 

Code provides that the neutral may be sized for the load. This implies that the load is serviced with an appropriate overcurrent device.