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  • Power Feed Tripping GFI

    Hello all! The x axis power feed on my mill is plugged into an outlet that has a GFI circuit. For some reason it has been tripping the GFI. I cleaned the gears and made sure that there were no chips or debris locking it up. I can turn it by hand and it does not trip the GFI at a low load - it did before cleaning, but now doesn't unless it is going at a higher rate or is feeding material. What might be the cause?

    Sent from my SAMSUNG-SM-G900A using Tapatalk

  • #2
    I think your problem is that SAMSUNG-SM-G900A that is using Tapatalk. They have been infamous for causing leakage currents in everything within a 10 meter radius.

    Seriously, a GFI outlet trips when there is a leakage current flowing directly to ground from some part of your circuit. The problem is probably defective insulation somewhere in that circuit or perhaps a wiring error. Have you kept the ground and the neutral completely separate when this was wired? In a GFI circuit if neutral is grounded anywhere, it can cause it to trip. Otherwise, you may have to use a high range Ohm meter (megger) to find the problem.
    Paul A.
    SE Texas

    And if you look REAL close at an analog signal,
    You will find that it has discrete steps.

    Comment


    • #3
      Does the x axis power feed have mains filter inside as they can cause leakage to neutral etc

      Peter
      I have tools I don't know how to use!!

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      • #4
        Exactly which model of power feeed?

        If it's a genuine BP 6F or 8F, then yes, it will often trip a gfci. The 6F has an SCR/Diode bridge directly across the 120v mains and has filters and caps to ground. Take care probing around - the derived common is at -170VDC; use an isolation transformer. If you use a scope you need an isolation transformer anyhow just so you can clip your scope probe grounding clip to the common.

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        • #5
          I have an import model. Super Power Workhorse "Super 250". It has worked fine for over a year now since I purchased this used mill. I was told that it worked prior to me buying the mill and I do not have a reason to doubt that claim. It just recently started to act up. It occurs when there is a load applied. If I run the power feed without the drive gear installed (I removed it to clean it) it does not trip. It either trips when engaged or if you turn the feed speed up.

          I will check the external wiring first then see what might be going on inside, but electricity and I do not get along.
          Last edited by Guncraft; 10-11-2016, 02:16 PM.

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          • #6
            Any idea what would cause it to just happen with no problems for the last year?

            Sent from my SAMSUNG-SM-G900A using Tapatalk

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            • #7
              I like the previous answers from both Paul A and Lakeside - AC is one of my weakest fields no pun intended

              but for what it's worth everything in my shop was fine till I installed an older model shop heater with only two wires and no ground, then the GFI would trip instantly - due to the unit sitting on the cement - as soon as I raised it off it was fine, that is as long as I did not connect it to the gas line that ran to ground lol

              my Mill sits on a piece of plywood and wonder if this would take care of your problem? and if it did would not the GFI still give you protection while you were handling it? or would it trip the second you touched it due to you standing on the ground? again more stuff for the experts to chime in on not me.

              Comment


              • #8
                GFCI outlet could be going bad.
                Gill

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                • #9
                  I checked the GFI outlet with a tester and it tested OK. I then ran a power cord around the corner to an outlet on a separate GFI circuit. It tripped that GFI as well. I then plugged the extension cord into a non-GFI circuit and it worked fine. What to do now? The whole garage is on a GFI circuit. What has me concerned is that it worked for a year and now started this issue. What is the hazard in running the power feed on a non-GFI outlet? What I the harm of running the power feed with this ground leak issue?

                  Sent from my SAMSUNG-SM-G900A using Tapatalk

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                  • #10
                    If you lose the ground to the machine it's possible for the leak to raise the surface potential to deliver a fatal shock. Take care.
                    Last edited by lakeside53; 10-11-2016, 11:38 PM.

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                    • #11
                      Originally posted by Guncraft View Post
                      I checked the GFI outlet with a tester and it tested OK. I then ran a power cord around the corner to an outlet on a separate GFI circuit. It tripped that GFI as well. I then plugged the extension cord into a non-GFI circuit and it worked fine. What to do now? The whole garage is on a GFI circuit. What has me concerned is that it worked for a year and now started this issue. What is the hazard in running the power feed on a non-GFI outlet? What I the harm of running the power feed with this ground leak issue?
                      If the GFI is tripping, that means that electricity is going somewhere that it should not. Power should flow between the hot and the neutral and nowhere else. GFI trips at very small levels of leakage because it does not take much to stop a heart if electrocuted.

                      If it trips at higher speeds there is a chance that something ls arcing to ground as the voltage increases. That could be a bit of swarf that is too close to the brushes or even a wire that's been contaminated by grease.

                      I would wire an ammeter into the wiring of the ground to see if there is current running there. I would not run it on a regular breaker. Regular breakers don't care if the power runs through the load and then ground.


                      Dan
                      At the end of the project, there is a profound difference between spare parts and left over parts.

                      Location: SF East Bay.

                      Comment


                      • #12
                        Originally posted by Guncraft View Post
                        I checked the GFI outlet with a tester and it tested OK. I then ran a power cord around the corner to an outlet on a separate GFI circuit. It tripped that GFI as well. I then plugged the extension cord into a non-GFI circuit and it worked fine. What to do now? The whole garage is on a GFI circuit. What has me concerned is that it worked for a year and now started this issue. What is the hazard in running the power feed on a non-GFI outlet? What I the harm of running the power feed with this ground leak issue?

                        Sent from my SAMSUNG-SM-G900A using Tapatalk
                        My advice here needs to be "guided" but - you can individually wire your GFI's so that you can have protection to other circuits and leave the power feed one on it's own - will take more than one GFI,
                        and as Lakeside stated might not be a good move -

                        Comment


                        • #13
                          That heater scares me. There is obviously a conduction path to the external frame. Hopefully it is just leakage, but it can be a more direct short. I would disconnect it and use a regular Ohm meter to see if either side of the AC plug shows any conduction to the outer frame. If so, you should find out why and correct it. AND install a three wire cord on it: connect the hot and neutral as they are now (with any needed corrections) and the green, ground wire to the outer frame. That way, if there is a short, it will blow the breaker and you will be safe.

                          Back to the power feed: someone said there could be some filters between the line (hot and neutral) and ground. But ground is not present unless there is a ground wire in the power feed, so do you have one? Anyway, if there are filters that are connected to ground (and hence to the frame of the machine) then they would be very suspect. Perhaps there are some capacitors there that have become leaky over time: electrolytics can do that with age.



                          Originally posted by A.K. Boomer View Post
                          I like the previous answers from both Paul A and Lakeside - AC is one of my weakest fields no pun intended

                          but for what it's worth everything in my shop was fine till I installed an older model shop heater with only two wires and no ground, then the GFI would trip instantly - due to the unit sitting on the cement - as soon as I raised it off it was fine, that is as long as I did not connect it to the gas line that ran to ground lol

                          my Mill sits on a piece of plywood and wonder if this would take care of your problem? and if it did would not the GFI still give you protection while you were handling it? or would it trip the second you touched it due to you standing on the ground? again more stuff for the experts to chime in on not me.
                          Paul A.
                          SE Texas

                          And if you look REAL close at an analog signal,
                          You will find that it has discrete steps.

                          Comment


                          • #14
                            I don't want to get zapped... I have no way to fix it. Would a general electronic shop be able to fix it?

                            Sent from my SAMSUNG-SM-G900A using Tapatalk

                            Comment


                            • #15
                              This feed, is it a variable speed drive?

                              Then it varies either voltage or frequency, possibly pulse widths, to vary speed.

                              If so, it is possible that there is NO ELECTRICAL FAULT at all in the motor.

                              The variable speed electronics could be misbehaving in a way that makes the GFCI trip from capacitive currents. tripping at higher speeds can be due to a difference in waveform in the drive output at higher speed. The drive may be working up to a failure.

                              A filter capacitor on the drive may have become disconnected and unbalanced the leakage.

                              Or, of course, there may be an actual safety fault, but it seems less likely due to it working some of the time, and especially since it works without incident on a normal grounded outlet. A bad fault would blow breakers, etc.
                              CNC machines only go through the motions

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