Help me Make my GCFI Stop Tripping

[gerritv]

I don't know if I was clear. I believe the friction from the bearings caused the GFCI to trip.

Yes, I understood what you believe. However you do have a meter so it seems best to just check for total isolation of hot and neutral from ground/frame? And that the cable from machine to wall is actually wired correctly.

 

[Chips O'Toole]

Why would removing the belt prevent the GFCI from tripping, if the motor is the problem?

I will go back over the wiring, but the bearings are the big problem right now.

 

[gerritv]

Why would removing the belt prevent the GFCI from tripping, if the motor is the problem?

The load/overload could be causing enough increase in leakage from hot to neutral/ground to trip the GFCI.

 

[GL]

I had random trips on a GFCI outlet in the basement. It had a refrigerator and a deep freeze plugged into it. The research I did at the time indicated that GFCI outlets like resistive loads but not inductive loads (like motors starting). Since these appliances were in the basement, and you don't look at them often, a trip can be a major expense. So, while not to code probably, the outlet was pretty high on the wall and I have a gravity drain to let any water out, I changed to a standard plug and got on with it.

I suspect the "belt off doesn't trip the outlet" is the difference in induced load when the rest of the machine has to spin up.

 

[hman]

The GFI (RCD) should be rated , mostly in europe they are 30mA or 50mA
30mA is considered good for life protection ,

THANKS, stupoty! That video does a MUCH better job at explaining a GFCI/RCD than I did.

 

[hman]

Why would removing the belt prevent the GFCI from tripping, if the motor is the problem?

Admittedly a wild theory: It might be that there's some kind of high resistance "short" to the rotor somewhere inside the motor. Belts, though they are rubber, are loaded with carbon, and may well be slightly conductive. Installing the belt would allow the leakage to get to the frame of the machine. Removing the belt gives the leakage nowhere to go. This assumes that your motor is mounted with rubber isolators at each end, and is not otherwise grounded. If the motor frame is hard mounted to the machine it will provide a leakage path to ground, and my scenario would be invalid.

I suppose you could test this theory by removing the belt, turning on the motor, connecting test lead to the machine's frame, and briefly touching it to the motor shaft. If this pops the GFCI, look for an internal current leak to the rotor.

 

[stupoty]

Admittedly a wild theory: It might be that there's some kind of high resistance "short" to the rotor somewhere inside the motor. Belts, though they are rubber, are loaded with carbon, and may well be slightly conductive. Installing the belt would allow the leakage to get to the frame of the machine. Removing the belt gives the leakage nowhere to go. This assumes that your motor is mounted with rubber isolators at each end, and is not otherwise grounded. If the motor frame is hard mounted to the machine it will provide a leakage path to ground, and my scenario would be invalid.

I suppose you could test this theory by removing the belt, turning on the motor, connecting test lead to the machine's frame, and briefly touching it to the motor shaft. If this pops the GFCI, look for an internal current leak to the rotor.

Thats a good thought , also could possibly be some issue with the centrifugal switch perhaps when the motor is stalled at start. I had one motor that was a little susceptible to swarf and this being a grinder there is high likelihood of a little dust being inside and it's probably quite conductive.

(some single phase motors use a seperate starting relay to switch it but i'm less familure with this kind)

 

[Flyinfool]

It takes 10 minutes and no cash to test the electrical. (You already have a meter) I do not understand the reluctace to eliminate the easy stuff before spending a lot of time energy and money replacing parts?

 

[stupoty]

It takes 10 minutes and no cash to test the electrical. (You already have a meter) I do not understand the reluctace to eliminate the easy stuff before spending a lot of time energy and money replacing parts?

I think he (OP) said there was a separate issue with stuck bearings in the spindle which he found when he took the belts off.

He did mention he was going to check the motor out a bit.

It's all a todo list with things to check off

Stu

 

[Chips O'Toole]

I can give you several reasons why I'm not looking at the electrics closely.

1. I have a virus, and I don't feel like doing too much right now. This is the primary explanation. I somehow managed to get pink eye at my advanced age. I started having symptoms on the same day I finished welding my arbor press stand, so I thought I had a flash burn. That was an interesting experience.

2. The behavior of the grinder suggests that fixing the bearings may end the GFCI problem.

3. No new bearings, no grinder. If I can't fix the bearings, it doesn't matter whether the motor works.

4. No one has given me any information that would help me open the motor up, so even if there is something wrong with it, I can't get inside it yet. No one has even told me whether it has capacitors.

5. I'm also trying to get air lines installed in the shop.

I have read that the only way to test a motor's windings correctly is to use an expensive megohmmeter I don't have. If that's wrong, feel free to let me know.

I'll post a photo of the motor. I don't have a shot of the nameplate right now. It's a 1/4-HP GE. I believe it says "Type M" on it. I haven't made any effort to find out what that means. In the photo, you can see the rubber mounts which I don't know how to remove.