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Thread: three phase wiring question

  1. #1

    three phase wiring question

    Table saw got moved but nothing changed.

    On re hook up with the power off at the mains I noticed this. Used as a continuity tester my meter is beeping between line 1 and 2. Makes no sense to me so figured a short in the wiring. Traced back to the saw and took the lines 1 and 2 off so now only the saw in the equation and the meter on the line 1 and 2 saw internal wiring and it beeps. I checked some other machines and found the same on one other SCM machine only in that case it was line 2 and line 3 that beeped (again with the power off)

    I think this will happen on a transformer but there is no transformer now as i test the lines into the saw. I tried one other SCM machine and there is no beeping on any combo of lines.

    I was hesitant to run the table saw but it was checked by an electrician in the first place. He found the master shut off had been bypassed on one phase of the switch, and the push on start was also not working. I took that apart many times and got it to work. Nothing was changed so I ran it and fine for the short time I did but why does this happen.

    Last edited by Warren Lake; 03-22-2020 at 1:38 PM.

  2. #2
    Are you sure there isn't a small transformer (for powering controls or something) hooked up?

    There is nothing about 3 phase that causes this situation to be any different than a "regular" circuit - if your ohmmeter is showing continuity, it's because there's something hooked between those wires.

  3. #3
    thanks Dan,

    Internet out all day, up here its a piece of string pulled between two cans, when they update us to fibre optics will likely be clear fishing line.

    here is inside the saw box where the power cable comes in. Here ive retaped it but had used the continuity tester taking off the lines to the disconnect so I was only using the saw wires and got beeping.

    The black tape on yellow marr is line 2, the next red tape is line one. I took the marrs off and the continuity tester beeps when on line 1 and 2. I dont get it. Ran the saw for half an hour and it ran great. This is why it showed up at the disconnect, its from the saw. At the disconnect I thought a short in a wire followed back then took it off so only the saw involved? Then there is an SCM shaper with 1 and 3 beep, on that one I only measured on the disconnect box. That one is hooked up with a transformer at the end and power off.

    Sorry if im not explaining this well enough, Dont know if there being two motors in the saw have something to do with this. THe shaper would have a second botton for the power feed on and off.

    Last edited by Warren Lake; 03-23-2020 at 2:05 AM.

  4. #4
    Join Date
    Dec 2006
    Toronto Ontario
    Warren, the object on the upper left looks like a control transformer.

    As Dan indicated that's what your continuity tester is detecting............Regards, Rod.

  5. #5
    yeah ive left it at that and run the machine a number of times and its fine. NO blown coil or. It was odd to measure at a disconnect box and get the beeping and think there is a short somewhere. Another machine measures that way but its on line 1 and 3, since its a roto line three is manufactured. You cant put that line to a coil. Does it affect a transformer in anyway like it does with a coil?

  6. #6
    Join Date
    Dec 2006
    Toronto Ontario
    Hi Warren, yes it does because the transformer runs the contactor coils and any other control components.

    The transformer should be connected to the non manufactured lines........Rod.

  7. #7
    went across the top of the box and beep between all combos. Power is off but transformer in the circuit so that is the cause. Thanks for telling me that from the past

    Left the table saw and thanks for that transformer explain. No more concerns on that other than more set up time

    Just as well this happened its a measure i would not normally do, so now on the T130 im beeping on line 2 and 3. Im sure this was sorted out by an electrican and based on what you are saying the coil is seeing manufactured power. Im lucky it hasnt taken out the coil. I can logically change the wiring but now a bit concerned since its been fine as wired, I get that can be luck of the draw and it just hasnt happened yet. I checked the machine at the machine and same two and three beep so black and blue wires. Im glad I asked and thanks for that answer. Every machine has a different story.

    thanks Dan and Rod both for your help so far.


    Line 2 Line 3 BeepA.jpg
    Last edited by Warren Lake; Yesterday at 6:10 PM.

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