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Re: Three phase conversion In Rush current Concern.



Original poster: Don Murray <don@xxxxxxxxxxxxxxx>



Tesla list wrote:
Original poster: David Dean <deano@xxxxxxxxxxxxxxxx>
 He had made his own rotary
converter from a three phase motor and no capacitors at all.  He had a small
1PH motor hooked up to a large 3PH motor with a kinda loose belt and some
missaligned pulleys.  He demonstrated the operation for me. First the small
motor was started and the belt slipped till the big motor caught up with it.
Then 1PH power was supplied to the big motor, and as it took over, it would
throw the belt. Then the small motor was turned off and the big motor idled
along on 1PH power generating the third phase all the while. It worked. The
guy claimed it had been working like that for years. It probably worked
better than the 1PH motor with the start winding brought out I made and used,
but the belt thing just did not tickle my fancy. But it goes to show that
there are probably as many ways to do something as there are people to try
it.

Besides using a pony motor to spin these up, I have seen people use a rope and start them like a lawn mower. Once they get it spun up they just close in the single phase to it.

For a 20Hp you'll end up somewhere between 80 and 100uf between one utility hotleg and your manufactured hot leg. And 200 to 300uf between the other utility hotleg and the manufactured hotleg. It's trial and error by trying +/- 5 to 10uf on each side. Say you're manufacturing C-phase, if you can get voltages something like A-C phase 240V, and B-C phase 220V, you'll be doing good.

Don