Inverter or RPC.

Hi Guys,
In the large end of my shop I will have several machines that will be 10 to 20 horse power.
For the little machines ie Bridgeport, Monarch EE, surface grinder, I will use my trusty 5 HP RPC.

My question is this, given your choice how would you power the "High" horse power end? It is a one man shop, so only one of the large high amp machines will be on at any given time.

I don't need VFD only an inverter to get three phase, or should I just build a 25 Hp RPC.

Any guidance on this subject?
Thanks JB

"Any guidance on this subject?"

I would seriously investigate, and consider, conversion from three-phase to single-phase capacitor start/capacitor run, a la H-A-S.

Enough information is contained in the H.A. Steelman patent ...

U.S. Pat. 2,922,942

... and in the Steelman Industries Inc literature ...

H-A-S Converter

... for the enterprising hobbyist to do most of the work himself.

This is the link for the HAS static converter instalation. I am impressed with them on irrigation wells. Have some going 20 years with no problems. Heavy duty built product.

http://www.capacitorconvertors.com/pdf/staticinstructions.pdf

Oilfields and irrigation are Steelman Industries' main users.

Not a thing about the method which is not applicable to machine tools where variable speed is not required on account of other means, say, a belted or geared headstock, etcetera, being available for speed control.

An H-A-S converter should not be thought of as a simple starting means. It provides a starting means, of course, but it also provides a running means where 100 percent of nameplate power may be achieved.

Steelman's instructions, see the PDF file referenced above, shows how to apply the device to a number of applications, including a machine tool's reversing magnetic motor starter.

I have a question also about running a single piece of equipment with a 20hp 3 phase motor. I have a lathe that might one day move to a shop that doesnt have 3ph power and have been considering different options for powering it. After researching and building my small 3hp RPC it would seem that it would take a lot of work to build a big enough RPC to run the lathe. My thought is to make a pony motor set-up to start the existing motor. What would the problems or drawbacks be to this?

Shawn,

A 20 hp RPC is possible and not too hard to build. I would prefer this to any type of pony motor contraption.

Another idea, presented here, is a multiple idler RPC. For instance you could build a RPC consisting of two 10 hp idlers and you could then run one idler when using smaller machines then run both when running the large motor.

The H-A-S converter is a real good system but has one drawback--you MUST have a 12 lead motor or have a 9 lead motor converted to a 12 lead.

I have a 3 hp H-A-S and a 3 hp jointer that has been converted to 12 lead. I hope to finish the jointer refurbishing around Christmas and give the H-A-S a try. I think it is a real good idea and is why I posted it here some months ago. I am interested in feedback from anyone giving this a try.