Built my own Rotary Phase converter, but....

Robert Hyland · Jun 7, 2002

All the on line material I've read about building your own phase converter warns about L1 and L2 being OK, but Phase 3 being low and requiring "balancing." What does it mean if I get too much voltage on phase 3? L1 = 237.6VAC, L2 = 238.4VAC, but 3rd Phase = 254.3VAC. How do you "balance" it smaller...?
Robert in Tacoma, WA

halfnut · Jun 12, 2002

Unless this is feeding electronics or such you really don't need to worry. Motor doesn't know the difference. Keep this generated leg off such things as relays if you can. Where close voltage balancing is important is when dealing with CNC equipment, tis the reason that CNC compatable converters are so expensive.

joel · Jun 12, 2002

Phase 3 is low in current, not voltage. The caps allow you to balance the current. I used a homemade 7hp rotary that had similar voltages as yours. I had 11 Amps on legs 1 and 2, but only 3 Amps on leg 3.

As you balance the current, the 1 and 2 leg voltages increase and the third leg drops. The goal is to get the 3rd leg amps up closer to the first 2 without getting the voltages too high.

I never got around to balancing mine and I ran it for years without any problems.

leroy · Aug 31, 2002

Rob, you have to either switch in more or take out some of the run capacitors on the Made leg. Shoot for plus or minus 7% on the voltage. What you have now is really ok, but that high leg will tend to run a little hotter than the others. You will also notice that if you start and run some more motors that this condition will improve. The more "electrical iron" you have running will help absorb the capacitance and redistribute it into a triangle more closely resembling an equilateral. Just try not to use the made leg as a contol voltage and you should be good to go.

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Built my own Rotary Phase converter, but....

Robert Hyland

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halfnut

Cast Iron

joel

Plastic

leroy

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