RFC using 30 hp idler 10 hp mill transformer 230 to 460

The 30 hp fla is 36. The 10 hp fla is 12. My step up xformer is 20 kva. How large should my motor starter be? Will a portable generator be large enough? Thanks for your advice.

Raymond Klapka said:

The 30 hp fla is 36.

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... on "native" 3-P it may be.

Operated off singe-phase as an idler, that figure is much higher.

I have but a nominal 200 A single-phase service, would like to still have a functional home and shop so 10 HP is my self-imposed limit for any single idler.

Easier to start. Easy to add supplmental idlers once the "pilot" one is up and running.

I'd guess for a 10 HP load you might need but a 10 HP idler and 5, 7.5. or 10 HP supplemental idler, or even just two 7.5 HP.

..
Will a portable generator be large enough?

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To do WHAT? Portable can be hand-held or barge-mounted "large"?

This belongs in the forum for Transformers, Phase Converters and VFD's.

When you report it there, include more information- such as:
FLA at what voltage?
What kind of converter are you planning to build? I assume a rotary started with a pony motor. When you say starter, do you mean the pony motor, or the contactor starting the RPC? (starter motor, or motor starter)

The answer to the last question is YES- if you can afford it.

The question you should be asking is if it would make sense to get a 3 phase generator to run the machines. For most the answer is no, but if I lived in some areas of California I would at least consider it.

Thanks for the responses. As clarification,I’m using a half hp pony on the 30 hp 460v 3ph idler. The motor starter would connect from my generator to the 240/480, 20 or 25 kva xformer. The 480 feeds the idler and the 10 hp 460v 3ph mill motor. I plan on two capacitor banks of 224 micro farad @ 525 v between the two active windings and the fantom winding.
Does this seem reasonable?
Thanks for your comments.

You really ought to re-post your question in the Forum for Transformers, Phase Converters and VFD's.
That is where the members with the background to give better answers will be found.

As I understand your plan, you will have a generator feed 240 volts to the phase converter motor controller.
The motor controller provides power to a transformer of 20 to 25 kva, which converts the voltage to 460 volts.
The transformer then provides power to the 30 HP rotary phase converter, which has been spun by 1/2 hp motor of ? voltage and phase.

That is not how I would arrange things.

What I would suggest is having the generator feed the transformer, with the transformer near the generator. This means you have a short length of heavier gauge wires between the generator and transformer, and the wires to the RPC can be a smaller gauge due to the higher voltage. This saves you money.

At the RPC I would use a small step-down transformer to power the control circuits. This runs directly off the 460 volt feed to the motor controller. The step-down transformer powers the momentary "ON" and " Emergency OFF" push-buttons, and other control circuits The momentary ON button activates a latching relay which allows power to the the control circuits. When the control power starts, it (1)activates a contacter and a timer. The contactor starts the pony motor, which runs until the timer cuts the power to the relay. (2) starts a second timer which activates the motor starter, and powers a contactor connecting the run capacitors to the system.

If you have the capacitors connected as you spin up the idler it can act as a generator and limit the speed you can get to, and being out of phase from the mains current, can lead to some significant starting inrush current.

You have not said what the capacity of your generator is. If the only machine you run is the is the 10 HP mill, the 30 HP idler is more than you need. The disadvantage is that the inrush current starting the 30 HP idler on a single phase current is going to be significant. This may overload and kill your generator. On way around this would be to have several smaller idlers start in series- for example, the RPC starts with one 10 HP idler, then 10 seconds later a timer starts a second 10 HP idler.

Raymond Klapka said:

Thanks for the responses. As clarification,I’m using a half hp pony on the 30 hp 460v 3ph idler. The motor starter would connect from my generator to the 240/480, 20 or 25 kva xformer. The 480 feeds the idler and the 10 hp 460v 3ph mill motor. I plan on two capacitor banks of 224 micro farad @ 525 v between the two active windings and the fantom winding.
Does this seem reasonable?
Thanks for your comments.

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Not enough information.

I would replace the genset with a 3 phase unit.

While I own a 30kw genset, it is only single phase, for backup power.

This sounds like what you have.

digger doug said:

I would replace the genset with a 3 phase unit.

While I own a 30kw genset, it is only single phase, for backup power.

This sounds like what you have.

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"Sound" where? Which post told us the gen set size?

MIL-SPEC ones large enough, one also sets up for 208/416 Wye.

If, then you still need a transformer at all? It would be a step-DOWN one to haul the lower-Voltage single-phase loads.

Is there single phase from utility mains AT ALL?

10 HP Mill? Manual? CNC?

Is the 10 HP motor the ONLY load on the mill?

What ELSE needs power? Other machine tools? Lighting? HVAC?

I did say "Not enough information"?

And ANY gen set over 5 KVA can be BETTER all-around with at least 3-P option.

Balancing loads, Circuit-breaker and wire-sizing thing.

You guys need to take a reading comprehension course. He doesn't want a rotary phase converter (RPC). He is asking about a rotary faze converter (RFC), dawg. Like yo, dem phat boyz better get up in that shit, homie. My boy is runnin' a mill that got all ate up with motor, G.

GregSY said:

My boy is runnin' a mill that got all ate up with motor, G.

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Damned Are-Ate collets just will tear s**t up, won't they?