The reasons people use idler motors is to increase the starting and
running torque. A three phase motor run on single phase power will
produce about 2/3 rds the power it would produce on three phase power.
Also with an idler motor you can reverse the motor rapidly ( well
maybe ). Used three phase motors are pretty cheap, so using one is
not a lot of money. But as you say, you don't have to.

Dan


(PeterKe) wrote in message

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



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