RPC hookup questions - breaker sizing, neutral wire to load for 110V?

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Gronk

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MI
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Engineer
Long time lurker, first time posting. Tried searching for details but can't find a clear answer to my questions so I'm hoping to get it cleared up here. I've watched Mike's study guide videos for sizing conductors and circuit protection for motors to get the background info and I think I understand it.

I'm hooking up a rotary phase converter for some small 3-phase machines in my garage/shop. It's a 5hp American Rotary panel with a 3hp idler. Current machines are all 1-1.5hp but I'm wiring for 5hp in the event I upgrade the idler. I'm going to use a SO cable with twist-lock NEMA connections to connect whatever machine I'm running at the moment.

My main questions are on the RPC -> machine hookup.
  • I've spec'd 30A plugs/receptacles to give me room for 5hp loads. AR recommends matching the load-side breaker to the receptacle. NEC 430.250 lists 5hp FLA as 15.2A @ 230VAC 3ph. That means 30A breaker is within the 250% rating on 430.52 for short circuit protection and is high enough to prevent nuisance tripping, correct?
  • Since I'm dealing with a center tapped delta supply, I want to run a neutral out with the 3-phase and do "courtesy outlets" on the machine instead of wiring separate 110 sockets on the wall or adding transformers into the panels. Is this the wrong way to go about this?
There's more questions about conductor sizing/derating but that depends on what direction I go for the 110 outlets on the machines.
 
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Looks like maybe this belongs in a different sub, maybe Calculations/Engineering for the breaker and wire ratings? I'm not sure where else to ask for adding the neutral line to the high-leg delta.
 
I am closing this thread, in accordance with the Forum rules. This Forum is intended to assist professional electricians, inspectors, engineers, and other members of the electrical industry in the performance of their job-related tasks. However, if you are not an electrician or an electrical contractor, then we are not permitted to help you perform your own electrical installation work.


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