Electrical issue with lathe spin down

[Dave Duane]

I don't know if this post belongs here, but since it involves my lathe it seemed like as good a place as any.

When I built my shop I put GFCI outlets at the front of each circuit. I'm not sure that was really necessary, but it seemed like a good thing to do. I've been having an intermittent issue lately when I shut my lathe off (a Jet 1642 EVS) the GFCI outlet at the front of this circuit trips. I have to walk over to that outlet and reset it. It only happens occasionally, and only when the lathe is spinning down, right after I hit the button to turn it off. The only other items on this circuit are a couple of 75W lights aimed at the turning.

Any ideas on what would cause this? The easiest solution seems to be to replace the GFCI outlet with a standard outlet and give up the extra protection. But, I thought I'd pick your brains first.

[Richard Madison]

Dave,
Am surprised that your 1642 runs at all on a GFI circuit. There is a hairy great technical explanation, but the bottom line is that EVS lathes and GFI's are rather incompatible. Suggest that you remove the GFI from that circuit.

[Bill Bolen]

Have to agree. When we built our home the Electrician advised me against any GFI in the workshop that might power tools. He said they would be tripping all the time...Bill..

[Jim Becker]

Yup...same experience for me.

[Steve Schlumpf]

Have to agree with everyone above - the GFCI outlets will prove to be very frustrating! They are designed to trigger on a surge in current - when you shut down your lathe (or start up for that matter) the GFCI will sense that surge in current and trip.

[charlie knighton]

when i setup my 1642 evs this summer i had the same issue with the breaker, i do not know what kind of outlet it was, but it had 2 four ft lights on outlet also, i had to run a dedicated line for the lathe, no problem after that

yes it is annoying, i turn the lathe off to more tool rest :eek:

[John Terefenko]

It is the electronics in the lathe that are tripping it. Are you plugged into the GFCI?? If you want to leave the gfci then just take off the rest of the outlets on the load side of the GFCI and wire them to the feed or line side of the gfci.

[Bernie Weishapl]

My electrician said no GFI on my lathe. He said they won't work. He does not recommend them for any power tool in the shop as a matter of fact.

[robert hainstock]

I do not have nor do I want any in my shop. Protect your electronice controlers with surge protectors. :eek::eek::)
Bob

[Von Bickley]

Dave,
I did electrical work for over 35 years and there are no GFCI receptacles in my shop and never will be.....:D

[Mike Cutler]

Dave the technical answer is that the variable speed drive on your lathe is being seen as an imbalanced load by the GFCI on shutdown as the electronics and the transformers collapse their field.
The GFCI is seeing an imbalance in current between the power leads and ground. It only takes a few miiliamps, for a few milliseconds and the GFCI trips.
Some equipment shouldn't be on them, and a variable speed drive with a frequency shifting controller is one. Circuit commons and earth ground may not be at the same reference. I'd put the lathe on a non-GFCI protected circuit.

I'm not certain that I agree with the blanket statements to have no power tools on GFCI's because of intermittent tripping. It may need a little more defining. I'm fairly certain I know what folks are saying.

At work, we have multiple dozens of power tools, portable and stationary, in use daily, for extended periods of time, in all types of conditions, and some fairly harsh environments. Every one of them is GFCI protected (OSHA). The intermittent GFCI fault rate is statistically zero.

The GFCI's are on the power cords themselves, or the extension cord, to protect the breaker at the panel from tripping, in addition to protecting the individual. Kind of backwards, I understand, but tripping any breaker in a Nuclear Power Plant, even on a general lighting panel, is a very big deal. Trust me.:eek:
Not trying to stand on the soap box or anything. Just kinda thinking we may want to define our statement a little better.

[Bob Hallowell]

You might be able to hook up a up a break resistor on the vfd, Might help balance the load and make it easier to spin down a big blank.

Bob

[Mike Henderson]

I agree with Mike Cutler. A GFCI essentially runs all the power leads through a differential current coil. As long as the net current (in and out) is zero, the GFCI will not trip. The problem with VFDs is that they generate a lot of harmonics and have large capacitors to ground to filter those harmonics (to keep from feeding them back into the electrical system). Those filter capacitors essentially "leak" sufficient current to ground that the GFCI detects an unbalanced load on the line and trips.

Almost no other woodworking tools have this problem. A regular electric motor, either universal or induction, will work fine on a GFCI and will not cause any problems.

GFCIs save lives and it's very foolish not to have EVERY 120V outlet in your shop protected by them. The only reason* to remove GFCI is if you have a tool that just won't work on them, such as a VFD.

Mike

*There's a few special cases where you don't want to use a GFCI, such as on a refrigerator - where a trip of the GFCI could cause loss of the food in the 'frig.

[Dave Duane]

Wow! What a great place. I really appreciate all the great information. I have a much better understanding of what's going on now, and I think I'll take the GFI off the circuit to the lathe - but leave them everywhere else. I haven't had any issues with any other tools in the five years I've been in this shop. Not until I got this lathe a couple of months ago. Thanks again for all the help.

[Dick Strauss]

OT-Pay special attention to Mike's last comment about refrigerators/freezers. We had a freezer running in the garage on a circuit protected by a GFCI (at the breaker). Something caused the breaker to trip. I discovered that the power was out on the garage curcuits within a day or so, otherwise we would have lost a freezer full of meat.

[Gene Michael]

It was great reading all the responses to Dave's question. The garage is my shop and the electrical inspector insisted GFCI's on all the circuits. They don't trip all the time, but often enough to be a pain. Sounds like nos is the time to pull them.:D