Using caps to balance 440V RPC

L2 is the "ghost" or "wild" leg, as I have heard it referred to. I carried that leg consistantly throughout the wiring (idler-transformer-lathe). ie: it is always the middle leg, wether leaving the idler, or going to the lathe, from the transformer.

Peace Milo

[snip]

Pictures are not allowed.

It is clear.

The autotransformer is three phase, as suspected. Changing taps on this autotransformer will have an effect to be sure, but not an obvious one.

Joe Gwinn

I have updated my drawing to show the caps installed.

'm at a loss as to how to even out the voltage. More caps? Chuck the transformer, and rewire the 440V lathe motor to 220?

Just to recap (no pun intended) Volt readings from idler (without being connected to transformer) A-C =238V, A-B=255V, C-B=218V

Readings from transformer output, with idler hooked to the transformer input.

H-1-H2=493V, H1-H3=501, H2-H3=517

Peace Milo

Sorry, screwed up the link.

There was a long thread on how to balance the phases. Do this on the

220 volt side of the autotransformer, as if autotransformer and motor were one unit. At least in theory this should do it.

Joe Gwinn

What is the autotransformer going to do ?

And is it linear like most or log based for lighting controls ?

A transformer isn't used to change the speed of an ac motor.

Mart> >

It's used backwards, to step 220 up to the 440 needed by the machine-tool motor.

Linear, made of copper and iron, intended for 3 phase. From what Milo has said, it's a tapped transformer.

True. This is a phase-conversion setup, not a VFD.

Milo published his schematic.

Joe Gwinn

Nothing on this end. make sure you remove oilfilter & the period after

Peace Milo

Ok joe -

I built one with a rotary and six transformers control blocks and the like.

The three boosted the 220 over what I needed and the other three snubbed the voltage downward. Mine is on a shop wall in a large water tight box and power distribution board.

Martin

Joseph Gw> >