That's the way I understood your description in the first place and when
you said no current in the third leg, I figured I'd read it wrong. I
use a 2hp idler to run a 1/2 hp on an old lathe and there is current in
the third leg. If there were no current in the third leg, you couldn't
start a three phase motor off a rotary converter.
BTW, using the old rope start rotary converter, if you started the
converter in the wrong direction (who could be absent minded enough to
do that?) The load would also run in the wrong direction. The load
certainly found something to use in that third leg.

bob g.

Charles A. Sherwood wrote:

With a static phase converter, zero current in the third leg is normal
(after the brief starting interval) when you are running a 3 phase machine
on single phase current. The third leg is only intergized for starting.


But in this case I have two motors in parallel. The big 1.5HP grinder
motor and the little 1/2 HP blower. The big grinder motor is pretty
much unloaded and the the blower motor which is always loaded because
it is moving lots of air. I expected to see some current in the third
leg but I don't see any.

chuck