"Jon Elson" wrote in message
...
Yes, a 3-phase motor also runs smoother than a single-phase plain
induction motor. Because of the power line cycles, the single-phase
motor is essentially shut off 120 times a second. Capacitor-run motors
are better in this regard, but a 3-phase motor is even smoother. Some
people have been troubled by bad surface finish and other vibration
problems and found DC or 3-phase motors solved the problem.

I'm surprised it could make that much difference. The motor that's being
replaced is a 110 repulsion/indeucion motor and the surface finish I get is
acceptable. One motor I'm looking at is a 110 capacitor-start. Any notion
of how that would compare to the old motor?

Later, you can always get a Variable Freq Drive for a 3-phase motor
and have variable speed, too.

I've been given a new Phase-A-Matic static phase converter that I would like
to use rather than hooking in to the RPC I use for my mill. The RPC is
rather noisy in my small shop and I'm hoping the static converter would be
quieter. Would a VFD replace a phase converter or be used in addition to
it? I'm assuming that the VFD will only vary the speed up to the rated RPM.
IOW, a VFD wouldn't allow a 1140 RPM motor to run more than 1140 RPM, but
allow one to choose 800 RPM for example. Does the power go down
proportional to the RPM?



Peter