Rockwell band saw motor tripping GFI

Happy Labor Day,
I am working on this 1947 Delta 14” band saw.
I am getting close, just need one more bearing and I thought I was ready to go.
I replaced the electrical source 14/3 wire. Plugged it in and the GFI tripped immediately.
I checked my work, all looked good.
I removed the end shield and cleaned the points. They were pretty bad. I also discovered a chaffed wire. One of 3, there are two sets of 3 wires. See pic.
I taped the damaged insulation assuming that was it. Blew all the saw dust out of the motor etc.
I plugged it and it ran perfect, for about ten seconds, then tripped the GFI.
I haven’t checked amp load yet.
This is a 115/230 ac motor. 1/2 HP, frame is 56. Rated at 7.7 amps at 115 v which is how it is wired now.
Please excuse the improper names I applied to the components, I really am an idiot when working on anything electrical.
I would like to save this motor. I’ll look for more shorts in the mean time.
Do you think it can be saved?

CA3F880A-61C0-4F0C-9662-A6936A8E1DC4.jpeg

9C141E88-808A-485F-A2C0-44868D996C87.jpeg
 
Continuity testing is a good place to start. The connection being wired for the right voltage is also important. With it reversing itself, something isn't right and that could very easily be the reason why it trips a GFCI.

For testing amp/watt draw on smaller loads, a kill-a-watt meter is about $20 at HF and others. It includes a pass through outlet, so no need to mess with wires or worry about shocking yourself.
 
I suspect the start capacitor or centrifugal switch if the motor is randomly reversing on start up-
Check the wiring is correct according to the diagram on the nameplate also
Test all motor wires with an ohm meter to the motor case- all readings should be very high resistance (250,000 ohms or more)
Mark
 
GFIs can trip for several reasons. I've seen them go when shutting off a small motor - the shaded pole type, no start winding. When you shut off the power to anything with a coil of wire, there can be a spark at the switch. That can be enough to trip an overly sensitive GFI. Could the 'ten seconds' have coincided with the centrifugal switch tripping as the motor came up to speed? The spark from that could have tripped it. Replacing the GFI might solve it.

Another sure tripper is if the neutral connection comes into contact with the ground. An intermittent contact could allow the motor to run until contact is made. The ground is connected to the neutral back at the service, but contact near the load creates a separate path.
 
Photo looks like white and green are together.

Check that.

Green needs to only connect to frame.

Check plug with ohm meter.

Safety ground needs to show as open to both line connections.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
Ok guys, thanks. I have the test equipment, I’ll have to relearn how to use them to test the ideas that have been shared.
It is a dual voltage, single can, single phase motor FYI.
 
Photo looks like white and green are together.

Check that.

Green needs to only connect to frame.

Check plug with ohm meter.

Safety ground needs to show as open to both line connections.

Sent from my SAMSUNG-SM-G930A using Tapatalk

Please NOTE this post. It is very important that the green power supply cable lead should only be connected to the frame and not the neutral.

The green provides the safety protection when not using a GFCI protected branch circuit.

David
 
I will take a picture of the wiring diagram and a detailed pic of the current wiring scheme.
I do see a green wire tied in with the yellow and blue/white on #4.
There is a green wire soldered to the board. It was one of the damaged wires.
I will check it out this evening.
Thank you
 
Sometimes manufacturers will use green wires for inside winding connections (they really shouldn't)
The only green wire outside the motor should be the ground (earth) wire
M
 
I checked the capacitor when I got home. This motor is done.
The wires have hard cracked insulation, every thing I check just tells me it’s time to let it go unfortunately.
I found one from Grainger for $115.
I didn’t want to spend the money but at least I can say it has new tires, new bearings and a new heart.
 
I don't know and you guys seem to know what you are doing, but another thought - we know GFCI outlets are sensitive to inductive loads, like motors with capacitive start so plugging into a non GFCI outlet works. Old appliances did not have polarized plugs. Maybe the ground pole indexes the polarity correctly? I have an old fluorescent light that, if you plug it in backward (just double prong) will zap you if you touch the housing, turn the plug over and it doesn't (yeah, nice, and I haven't used it since). If no ground, is that why it reverses direction?
 
Back
Top