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Building a Rotary Phase Converter

This page describes how I built one of my Rotary Phase Converters.

While most pages describe using a potential relay from Graingers I found them to be expensive compared to a local electrical supply house.

I started with a used but good 15hp 3-phase motor. If the bearings and windings are good your off to a good start.

You need a few things to build the self starting rotary phase converter.

To get the voltage between the generated leg and the real legs with a load it required about 3 times as much capacitors between L2 and L3 as between L1 and L2. I don't have a clue why but with any kind of load at all the volts are within a couple between any two legs. Without a load the generated leg will be quite a bit higher but you never run it without some kind of load so that means nothing.

A remote start stop can be rigged up using low voltage buttons and relay.

I have found out that for my Discovery 308 not to trip out when the spindle goes from 0 to 6,000 I need to overdrive the generated leg. So I added one more cap to L1-L2 and L2-L3 this put the voltage on those legs at 265vac and now the 308 seems happy to run like hell.