View Full Version : HELP!! How do i get the best size Rotary Phase Converter?

10-02-2007, 04:17 PM
My shop has grown, and all my bigger machines use 220VAC 3Ph. So far I have a 2hp motor, a 3/4hp motor and a 1/8hp pump. The problem I have is that a static phase converter can not run a fractional hp motor!

I was told by an electrician that I need to get a Rotary Phase Converter, one big enough to run all my machines! But they are not cheap! So I want to get one that I can afford, and one that will fit my motors!

Does anyone know how to choose the size of Rotary Phase Converter?


10-02-2007, 06:26 PM
. The problem I have is that a static phase converter can not run a fractional hp motor!

Does anyone know how to choose the size of Rotary Phase Converter?

Never heard of that, how come it cannot run a fractional?

The sizing of the RPC depends somewhat on what type of loads you have, i.e. transformer or 3 phase motor?
Any three phase motor is usually considered to aid the RPC.
IOW, if you had purely 3 phase motors as loads, the understanding that I had is that you could supply approximately twice the HP load as the RPC as long as the largest motor was no larger than the RPC itself.

10-02-2007, 07:24 PM
Hi Al,
My electrician responded with the same question!
The tech for the RPC informed us that their company Phase-A-Matic has been unable to make a static phase converter for fractional motors.

If I read your reply correctly, all I need is 2hp RPC to satisfy the needs of all my motors!


10-02-2007, 08:28 PM
This digital phase converter has been mentioned in a few threads.


It is not cheap but most posters who have it seemed happy.

10-02-2007, 09:00 PM
I ended up buying a 7hp American Rotary phase converter (http://www.americanrotary.com/). After searching prices, it was by far the cheapest rotary I could find but it's very nice. 7 HP was the smallest they have that's CNC rated. I don't know how important that really is but it works good. I believe they recommended double the motor HP of your biggest motor on the system. You could run all of your equipment from it then. In many cases you could run them simultaneously if you started the big machines first.

My understanding is that Digital Phase converters will only give you 2/3 the power as the third leg is only momentary for start-up. I looked at that PhasePerfect web site and it didn't look like it did that though.

11-11-2007, 07:22 AM
After talking on the phone to a local electrician, he recommended a 5 hp RPC! So I took his quote, and several others, and ended up buying one on eBay that is made by Baldor for $340

This weekend I will be installing the unit in my garage, and it's not a small project! First I had to figure out where to put the RPC, then I needed to locate a home for the control box. The box is 8" deep, so I cut out the drywall and recessed it to the wall! Then I had to go shopping for 3 phase twist lock plugs & sockets for all my machines. Lastly I will have to remove all the static phase converters currently in use, as they are taking up valuable space!

After lurking around Home Depot, I realized they do not sell any electrical components for 3-phase! So I had to get everything from Granger Industrial Supply! One thing for sure, I will not miss that annoying hum from the Static phase converters!