Lathe problem

[John Davidson]

I have have been building a shop for the last year. I started moving in the other day and when I powered up my Delta 1642 VFD lathe it tripped the ground fault outlet. When it first powers up there is no probelm the drive comes up and has no faults but once you press the forward or reverse button the outlets tripps. The motor does start turning in the right direction for a few seconds but then the drive sees the power loss and faults. I know the VFDs put a no linear load on the curcuit and am wondering if this could be the problem. Anyone else ever seen this?

[Ken Fitzgerald]

John...can you try your lathe on another outlet? I have my lathe and air compressor on GFI outlets and they work fine. However, I had an electrician look at my shop and he said after the final inspection, he'd take them out as they are often prone to failure when used on equipment circuits. Like I said....mine are working fine.

[Steve Schlumpf]

John, have to agree with Ken - try your lathe on another non-GFI circuit and see if it trips. First impressions would be the current spike when the motor actually starts to turn. Could be just enough to trip the GFI.

[John Hart]

Yup...Variable Frequency Drives as well as UPS's that covert DC into AC by way square waves will be perceived by the GFI circuit as a momentary short circuit....and trip. I would do as the others suggest and try another outlet...then change your GFI over to a standard outlet if it proves out.

[Bernie Weishapl]

Ditto what John H. said. GFI's don't work well with lathes or any other piece of shop equipment the draws high amps upon turn on.

[Bill Boehme]

I agree with what everybody else says. GFCI's look for a symmetrical load on both current carrying lines and when it detects a problem, they shut down. Unfortunately, the GFCI's are not sophisticated enough to handle the harmonic rich noise that VFD's put on the power line. Usually the problem can be fixed by using a line reactor on the line side of the VFD and helped even more so by using a load reactor on the motor side of the VFD. Some VFD's don't work properly if a reactor is installed on the load side so the operating manual for the VFD (not the lathe operating manual) needs to be consulted first.

Bill

[Mike Ramsey]

I Concur! :)

[Reed Gray]

Well, that is one I never thought of. I don't have any GFI circuits in my shop. I was thinking of the earlier version of this Delta Lathe, and it used to run on 110. It did require a dedicated 20 amp breaker, and thought that may be the problem.
robo hippy

[John Davidson]

Thanks for all the suggestions. I will pull an extention cord from the house to the lathe tonght and give it a try. It is on a 20 amp line and I use to run it on the GFCI curcuit in the basement with out any problems. But the house is 20 years old and I am thinking that maybe the new GFCI might be more sensitive to the harmonics of the nonlinear current draw of a VFD. I will let you guys know.