Making a Rotary Converter


Old 09-05-07, 09:50 AM
jn is offline
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Join Date: Aug 2001
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Making a Rotary Converter

A while back I saw a 3-phase motor running on 240 volt single phase power (it was running with no load) and a 3-phase milling machine was connected to a box above the motor that also powered the motor (perhaps to the three leads of the motor used as the converter). I'm not too cercerned about efficiency or if there is some reduction of power from the motor as long as it powers up an old piece of 3 phase equipment. Does anyone know what is involved to accomplish this?
Are relays needed? I never saw the contents of the panel to try and understand what was going on.
For now I am just interested in the basic concept, maybe later I could give more details to figure HP etc.

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Old 09-05-07, 12:30 PM
Join Date: Jan 2007
Location: Central Indiana
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Do some google searches for rotary phase converter or three phase converter. You'll start finding a lot of hits for various homebrew designs. Old wood or metal workers are also a source of designs to keep the old equipment running in home shops.
Old 09-05-07, 03:23 PM
Join Date: Mar 2006
Location: Wet side of Washington state.
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Talk about deja vu. Depending on where you saw it that could have been something that I made more than twenty-five years ago.

I had a friend, that had a friend, that had a vertical milling machine with a 2-speed, 3-phase motor. The motor had a special mounting so replacing it with a single phase 2-speed motor was out of the question. This man also had,or was going to buy, some other machine tools with 3-phase motors so I was asked if I could build a rotary converter that would power all of the tools if used one at a time.

I had previously built several static converters and this is why I was asked about the rotary converter.

I don't remember exactly how I did that rotary converter and I don't know if I still have my notes from so long ago. If you have only one 3-phase motor to run I suggest a static converter. I may be able to help you in the construction of such a converter.
Old 09-05-07, 05:20 PM
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Join Date: Mar 2007
Location: Bras D'Or, Nova Scotia ,Canada
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I've installed one of these rotary phase convertors but dont have a clue how to build one but I have seen several sites around the internet with what seem to be complete instructions and plans. As formula said.... Google it.
Old 09-06-07, 10:41 AM
jn is offline
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I read a few articles and ended up making one out of "junk" I had laying around from various projects. It worked fine and only required a motor and a couple capacitors. I was way overthinking it. I probably could have even got by with a motor and nothing else (if I wanted to pull start the converter motor with a rope). I just wanted to test an old piece of 3 phase equipment before loading the heavy sucker up and moving it to a bigger shop just to find out none of it worked. It functioned fine and is shipped out. The converter is back apart and on the shelf and the knowledge gained is packed away in the ol' medulla oblongata.

Thanks to all for your inputs

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