I have the above woodturning lathe and it's been acting strangely all of a
sudden. The complete sequence of events.
- Lathe runs fine in the garage/shop, although not much time put on it.
(bought it new)
- All of a sudden, every time I try to turn it on, it trips the GFI it's
- I use an extension cord to plug it into a non-gfi, and it works fine, for
a (very) little while
- Now, when i turn it on, (it's a capacitor start/capacitor run motor), it
doesn't kick over from the start capacitor to the run capacitor which is
usually accompanied by a definite "click" and a smoother run after it kicks
Is this what happens when a capacitor (the start) goes bad? Or is there
something in the kickover that can/has gone bad?
The motor has very little run time, this seems very odd to have happened
would the bad/going bad capacitor cause the gfi to trip every time?
Any help would be appreciated.
The click is a centrifugal switch, normally. If the motor does not come up
to speed the switch won't trip. If the contacts (points) are fused, it
won't trip either. This can be remedied by cleaning the points with some
400 sandpaper. WITH THE THING UNPLUGGED AND A MINUTE OR TWO FOR COMPLETE
Not sure if this is your problem, however. Have you given it a good blast
or two of air? The GFI trips if there's a short. Could be you've got some
gunk in there. I'd try that first. Not the kind of thing you want to do,
bypass a GFI. It's a safety device, after all.
I blasted the motor with air, I'm now going to pull the covers off of the
capacitors and blast that as well. hopefully that will cure the problem.
I'll also try to find the points you're talking about, although with the
small amount of run time, i *hope* that's not the problem.
Wasn't trying to bypass the gfi receptacle. just trying non gfi outlets to
try to pinpoint the source of the problem. At the time, I didn't know
whether the gfi had gone bad or not.
I agree, but it trips with and w/o extension cord. And the cord I used was
a 9' air conditioner ext cord, more than adequate. Also, there is the issue
that this started happening after everything working fine for a number of
Most likely -- your centrifugal switch is not opening. That switch is
IN the motor so it must be taken apart to get to it. Sometimes air
through the motor will do the trick but only sometimes.
If the start capacitor is bad (not very likely) it may not get the motor
spun up enough to kick the cent... switch. In this case you may be able
to spin it up by hand fast enough to kick it. That would prove that the
switch probably working right but the capacitor is bad.
If under warranty -- take it back.
Three phase motors don't have any of that 'stuff' which goes bad in
single phase motors. With the advent of less expensive vfds, somebody
needs to come out with a motor/vfd retrofit kit for various lathes for
those folks who are tired of screwing with capacitors and centrifugal
switches. That would also give you the low rpm and reversing which are
so sorely needed on so many Reeves drive equipped lathes.
Thanks for the reply. Since it's a tefc, I was hoping to avoid what you're
suggesting doing, which is take it apart, but oh well. Guess that's a
project for tomorrow. Just how long do those capacitors hold a charge
anyway? Not looking forward to getting zapped.
The capacitor on a single phase motor is there to produce phase shifting, to
create a "fake" rotating field. Since it is on AC, I don't see how it would
wind up with a charge when the motor is off. However, in case I am wrong,
just use a grounded clip lead to short out any terminal before you touch it.
if you think about it, the capacitor is across some windings to produce a
phase shift. Also, electrolytics have a pretty good leakage. Of course an
AC circuit can leave volts on a capacitor, it just depends where in the AC
cycle you turn it off - but I wouldn't worry - unplug and take it apart, by
the time you get it apart, the cap will be discharged. But, the cap is an
electrical part, it doesn't care about dust - you can pack it in dust and
nothing will happen unless the dust has a lot of water and shorts it out-
more likely welded contacts or dust keeping them from opening, or a broken
wire inside the motor.
Posted via a free Usenet account from http://www.teranews.com
Capacitor start motors are notorious for tripping GFI receptacles. GFI
receptacles are typically designated for use with portable hand held tools,
which a lathe is not. It sounds like your motor incorporates a centrifigal
switch which is not opening because it is worn out or fused together, or
full of crud.
Do you think I would be better off removing the GFI receptacle and
installing a GFI breaker instead?
The garage is on one breaker, and the gfi is upstream of the rest of the
receptacles. Are the GFI breakers less finiky than the receptacles?
I should probably just put in a sub panel, but I don't think I have the
*Single phase motors, (and particularly cheap single phase motors), and cap
start motors are notorious for tripping GFI outlets because they tend to
generate eddy currents in their windings and induce imbalances on the
conductors feeding them. They also reflect current and voltage spikes back
on the feed when they switch off of the start windings. In the early days of
GFI outlets, hair dryers were a big culprit. I don't know if the receptacles
are less sensitive now, or if hair dryers have better motors, but it seems
to have lessened greatly. I don't mean to say that lathes are restricted
from the GFI circuitry. I mean to say that the purpose of GFI protection at
the level of the outlet is targeted towards hand-held tools. That is why you
don't see a GFI on a washing machine. It is a stationary piece of equipment,
and the plug serves as it's disconnect for servicing. Same with a lathe,
unless it is a little tiny bench-top model. Even then, it is a grey area.
*That was not a reference to the GFI problem. It was a reference to a
seperately described situation. Go back and read the original text. (By the
way, any type of imbalance of sufficient magnitude will trip a GFI, not just
a "ground fault".)
Thank you for your responses. I've learned a lot and taken a lot of advice.
I opened up part of the motor today. Here's what I found:
Inside is immaculate, which I would have expected for a TEFC (hence the TE)
I now have an understanding of how the centrifigal switch operates, it was
operating smoothly, no fusing, no dust, no problem.
you almost have to see this to believe it. I posted two pics in
A piece which should have been installed on the shaft was rumbling loose in
there. There's no way it ever made it on the shaft during manufacturing.
The only amazing part is that this thing ever ran while plugged into a gfi.
I guess eventually this piece contacted the housing and caused the short.
I'm going to put it back together and see if it runs without this piece and,
of course, I'll be following up with JET. Even if the warranty period is
out, this is a definate manufacturing defect.
I'll keep everyone posted with what Jet does.
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