"JMartin957" wrote in message
...

My used 7x14 surface grinder appears to need a new motor, or maybe just
new
bearings. The spindle is belt driven and is currently fitted with GE
K163,
1HP, TEFC, 3450 rpm 3-phase motor. The motor is being driven with an
Hitachi L-100 VFD from a 220 VAC single phase line.

With the belts off the motor makes some noise on startup that sounds like
it
could be bad bearings. A cup of water sitting on the spindle housing
(spindle belts still removed) has some standing waves at full speed and
the
wave amplitude varies with speed.

snip

I don't claim any working knowledge of VFDs. I did look into them a few
years
ago when I was hooking up my 3 phase horizontal mill. I eventually
decided on
a static phase converter, which meets my needs.

One of the claims made about the VFDs was that the current they supply is
not
true 3 phase, but has some harmonics or secondary oscillations which can
cause
problems with some older motors. This seems to be rare, but might be your
problem.

Before you dump the motor, you might try driving it with a static or
rotary
converter.

John - that thought hadn't occurred to me. The noise on startup seems
indicative of bearing problems, though, so I'll check that first as soon as
I get the current project off the work bench so the motor can be looked at.

The motor installed (GE K163) still seems to be in production so it may be
OK with a VFD. It looks like it was a recent addition on the grinder,
though, and that is part of the reason why I'm asking about brands for
potential replacements. Maybe it's just not a good motor for a surface
grinder.

Mike