Has anyone built their own phase converter or have experience with purchased ones?
I am looking for a converter which can run up to a 5hp motor with a total connected load of 7hp maximum. I've seen homegrown ones using a 5 or 10hp 3phase motor and a small single phase motor as a starter which seem to be OK, but understand that they don't give true three phase power. Is this OK, or is there a better way. If it helps, the converter will be used intermittently to run a lathe, mill and possibly an air compressor.
I run my wood lathe (Oliver 19) off a converter that I bought 30 years ago, and it works very well. No problems, but the cost in early 70's was $300.
A site I found on digital phase converters is
Grizzly sells rotary (Motor/Generator) and Static (Electronic Inverter) Phase Converters. Judging from the prices the Motor/Generator is the better performing unit. It's probably less expensive to buy a single phase motor.Grizzly Phase Converters
I did a google.com search for phase converters a while back & came up with lots of detailed instructions on building several kinds.
Many years ago, I built one (not knowing how) but out of parts that didn't cost anything & had nothing to lose. I made a air compressor out of a 4 hp 3 phase refrigeration compressor. 1st try, I put maybe 4 ea. 40 mfd run capacitors & connected them between one single phase leg & the 3rd leg of the 3 phase motor. I did not have a unloader on the compressor so it had to start against head pressure. It worked OK till I jacked the pressures up to, on at 100 psi & off at 125, then if failed to start sometimes. I then added the first start relay I picked up & connected with 2 ea about 200 mfd start capacitors. It never looked back from then on. Ran it for years until it had a mechanical problem.
I often wondered, if had added 1 or 2 more run capacitor, would it have not needed the start capacitors.
Unit ran at well below nameplate amps, so I don't think it was hurting.
PS
Using refrigeration compressor for air compressor, you have to add oil regularly. This one had oil sight glass so it was easy to keep up with.
I wouldn't bet a plug nickel, but say the original motor was a star conected motor and you added three capacitors from each phase to a common point (not the neutral of the phases) and sized the capacitors using the relationship that no load apparent power equals the reactive power to be provided by the excitation capacitors. Then I don't believe you would need the start capacitors. For a 2Kw, 420v, 4 pole, 60hz, three phase motor that draws 3.5 amps this figures out to be ~40uF
(I would not take this advise if I was found of the motor or faint of heart)
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