How to Build a Rotary Phase Converter

[bobneumann]

Part 1: Theory, initial testing, and proof of concept

Part 2: Assembly, balancing and final testing

Plans and schematics:

[Junker2]

Wow, looks like you have discovered the elusive magnetic monoplole in your description of how a motor works. Better patent that pretty quick

[bobneumann]

Wow, looks like you have discovered the elusive magnetic monoplole in your description of how a motor works. Better patent that pretty quick

I told you physics nerds and engineers to plug your ears. Which one are you?

[mr herb]

The bearings in your 20hp motor sound rather tired. Are you going to put it outside your shop? I wouldn't want to have to listen to it all day.

While safety should be important, 47 years ago I built my first rotary converter, and never had all that complexity.

A delta wound motor works better than a star wound motor.

I have seen installations where the initial run up was provided by a rope wound around a pulley--like in an old lawnmower

I prefer a one half hp motor to do the spin up, then it can be disconnected, or just left running.. It wont draw that much.

Balancing the phases with no load connected wont do much, as any change in the load that your "floater" motor sees would require different capacitors. Better to balance with your largest tool motor running.

If your wall power goes off, and you have enough sense to turn off your lathe, I would hope that you have enough sense to turn off your converter motor also. If not maybe you should take up gardening.--Not you Bob, the you is directed to a reader

Bob, I'm not trying to criticize what you you did, you built a beautiful unit. I just afraid that you will scare off some fellows that want to convert single to three phase, but will get worried that it is too complicated. There are those that have enough sense enough not to stick their fingers on live terminals. There are a lot that don't have that sense, and realize it. This is not for them.

mr herb

[bobneumann]

I appreciate any honest feedback. Positive or not.

I don't have much frame of reference for how the bearings ought to sound. it's really not terribly loud in reality I wonder if maybe the microphone picked it up more than it should.

I'm no real expert on the engineering of it. The write up I was following recommended the balancing to be done under no load and give the generated leg 1.08x the voltage of the other legs. It seems legit enough to me. But I can't really say for sure how it will act under heavy load. I know that with the unit running and powering a 5 horse motor that the generated leg voltage dropped from 153 down to about 148. So it seems like under the unit's full load it's going to be in the vicinity of 140. Which is really all we're shooting for right?
In any case, I don't have any three phase motors big enough to really test it under its full load. But it's going to be used to power a 15 horse screw compressor. So I guess we'll find out just how efficient it is.

I sure hope that I haven't scared anybody off. My whole point of the video was to show that anybody with some basic electrical savvy can just step through the process one piece at a time and come out with a working unit.

But thanks again. And I appreciate your compliment.

[Frank S]

Bob you should be able to get some indication of how well it will respond to balance loading if you have a way to use additive resistance loading to any 2 of the output legs. Spin up load L1 & L2 take a reading of voltage for both legs and amperage draw then connect L1 & L3 the false leg to the same load take readings then repeat for L2 & L3 By the time you have completed the balancing you may find that you will even have capacitors across L1 & L2 to balance the incoming line voltages due to imbalanced loading elsewhere through out your supply IE the refrigerator starting up or someone using a Hair dryer.
I'm waiting for the 3rd educational video the first 2 were very explanatory as long as you said not viewing them from a physics or engineer nerd's eyes

[DIYer]

Thanks bobneumann! We've added your Rotary Phase Converter to our Electrical category,
as well as to your builder page: bobneumann's Homemade Tools. Your receipt:

Rotary Phase Converter by bobneumann

tags: conversion, electrical, motor