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Paul Drahn[_2_]

On 8/13/2020 3:43 PM, wrote:
I have an old Baldor grinder that's at least 80 years old. It is a
cap start and run motor. So the cap is always in the circuit of the
phase shifted winding. There is no centrifugal start switch.
It has always taken a long time to come up to speed but these
types of motors do that. However, it seems to take much longer to spin
up than my newer Baldor grinder motors that are wired the same.
The capacitor is a rectangular shape about 5/16ths of an inch thick
and maybe 1.5 x 2.0 inches. It has a brass case with cloth covered
wires coming out of the tar used to seal the case. I mention the cap
construction just to give an idea of how old it is.
I went through the motor a few years ago because the bearings were
bad. They had rawhide seals that had dried out, shrunk, and let grit
in. I replaced them with modern sealed bearings. The motor runs very
smooth. Just like a grinder motor should.
Today I used the grinder for about 1/2 an hour and it got pretty
hot. I was not loading the grinder very much because I was just
grinding points on tungsten TIG electrodes with a diamond wheel I have
mounted. Still, the motor got pretty damn hot. Could a bad cap do
this?
I suppose there could be some shorted windings. In any case, if a
bad cap could cause hot running I'll take the thing apart again and
replace the cap.
Thanks,
Eric

I suspect your motor has a single capacitor and is a split-phase motor.
Cap start, cap run requires two capacitors and the mechanism to switch
between the two.

A grinder has no reason the have a heavy load when it starts, which is
the reason for motors with two caps.

Paul