RE: [CAD_CAM_EDM_DRO] Mill Motor trips GFI outlet

GFCI circuits are notorious for tripping on inductive loads. As long as
the mill is properly grounded, you can safely get rid of the GFCI
outlet.
Lou

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jon Elson
Sent: Tuesday, November 06, 2012 4:52 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Mill Motor trips GFI outlet

On 11/06/2012 11:01 AM, Don wrote:
> I have a Leeson 1/4HP PM DC motor on my Taig mill and a treadmill
speed control. I only have 5 to 10 hours on the motor, it was new when
I acquired it. Yesterday, I was using the mill to cut the heads off
some rivets in some bed frame angle iron. Out of the blue, my bench
shut down. It turned out that it tripped the GFI outlet. I reset it and
started the PC and brought up Mach3, turned on the stepper driver power
and moved the mill away from the rivet and then started the motor. Just
as it was reaching full speed, it tripped the GFI again. I reset the
GFI and this time, only started the motor. I slowly increased speed and
again, just as it reached full speed, the GFI tripped again.
>
> I am guessing that one of the brush wires is shorting to ground, but
it seems that would cause a blown fuse in the control. There is no
moisture involved, so I'm not getting leakage there tripping the GFI.
Any words of wisdom before I pull the motor apart?
>
>
It is quite possible that the motor is filling with brush/commutator
dust. Most brush motors can be easily disassembled to clean the
commutator and area around the brush holders. There usually is a thin
plastic insulator that isolates the brushes from the frame, it is easy
for a buildup of conductive dust to develop electrical leakage. It is
also possible the spindle drive is developing leakage or electrical
noise that is fouling up the GFI, or it could be a bad GFI.

Jon


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