Folks - I'm curious, and would welcome if someone could explain
something for me. I notice on this and many other threads that when
the topic of making three phase power from single phase comes up,
often the use of an idler motor is proposed.

My question is. If you don't need the variable speed function ( ie use
a VFD ) why the use of a separate idler motor?

- I have a three phase motor on my drill press and I simply hooked it
up in Steinmetz connection - single phase supply across one motor line
and a suitably sized run cap ( about 50uf per hp ) from neutral to the
third motor phase. Admittedly the starting torque isn't great, but
most machine tools start on light-load conditions, and if it is a
problem it is simple to arrange for an extra start cap to be switched
in during startup.

Its not that I'm advocating one method over another, but the use of
idler motors seems so general that I'm assuming I've missed a point
somewhere along the way, and would like it if someone could explain
the pro's and con's

Peter


"wmbjk" wrote in message ...
"SRF" wrote in message
...

I'm setting up a hobby machine shop and am getting into the issue of 3
phase
motors. Most of the motors are going to be in the 1 to 3 horsepower
range.
For motors of this size, why would I want to have make three phase
power to
run these machines instead of just swapping out the motors for single
phase?

Thanks.
Steve.

Here's a site with some info.
http://www.processcontroltechnologie...seinverter.htm My only
experience is with the Toshiba S7. A very cool product, but probably in
the $800 range. This is the best I could do for a picture
http://www.lbelec.com/toshiba/drives.html It's the one shown in the palm
of a hand. Contact TK Electric at 702 293-2310 if you need more info.
Why would you want one? Smaller wire sizes, variable speed, variable
torque, slow startup, safety cutoffs, etc. Not really needed for
woodworking I don't think, and you wouldn't be able to make use of most
of the sophisticated programming anyway if you were running multiple
motors. Although if you have enough motors, perhaps adding one new
device would be easier than swapping them all.

Wayne