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  • Surface grinder motor trouble

    I recently picked up a Clausing 6x18 surface grinder, made in the 80's in Taiwan. Saw it run at the seller's spot, all was good. Got it home, wired it up, and it was good for a bit; did a bit of novice grinding, yada yada. A week later I go to fire it up and notice the wheel's spinning the wrong way, and it's having trouble starting the motor.

    Seems like nine times out of ten when you hit the start button, the motor seems to cog and stall, and eventually pop the overload on the contactor. It might spin a tiny bit before getting stuck. If you keep cycling it, eventually it'll start and appear to run fine.

    I fixed the reversed running by swapping a phase, but that's clearly a bandage as it was running the right way before. There was a loose wire going to the motor which I've since found and fixed, but the motor still struggles to start. There's ~230V between all three phases at the motor.

    Motor is a 1hp 3ph running off a 5hp-rated RPC; the phase converter runs a number of other machines with no change in direction or starting ability so I don't think it's that.

    Anyone have any ideas as to the issue?

    Thanks in advance!

  • #2
    I had the same thing happen with my abrasive 1 1/2 surface grinder but it did it from when I got it.
    I'm running it from a static phase converter so it may or may not be the same.

    Anyway I swapped two of the leads so it still ran in the correct direction but the source phases were swapped and it fixed the problem.

    All I can figure was that one winding was sensitive to the manufactured phase.
    Guaranteed not to rust, bust, collect dust, bend, chip, crack or peel

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    • #3
      Originally posted by isaac338 View Post
      I recently picked up a Clausing 6x18 surface grinder, made in the 80's in Taiwan. Saw it run at the seller's spot, all was good. Got it home, wired it up, and it was good for a bit; did a bit of novice grinding, yada yada. A week later I go to fire it up and notice the wheel's spinning the wrong way, and it's having trouble starting the motor.

      Seems like nine times out of ten when you hit the start button, the motor seems to cog and stall, and eventually pop the overload on the contactor. It might spin a tiny bit before getting stuck. If you keep cycling it, eventually it'll start and appear to run fine.

      I fixed the reversed running by swapping a phase, but that's clearly a bandage as it was running the right way before. There was a loose wire going to the motor which I've since found and fixed, but the motor still struggles to start. There's ~230V between all three phases at the motor.

      Motor is a 1hp 3ph running off a 5hp-rated RPC; the phase converter runs a number of other machines with no change in direction or starting ability so I don't think it's that.

      Anyone have any ideas as to the issue?

      Thanks in advance!
      The cog and stall is from single phasing. You might have a bad contactor.

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      • #4
        Originally posted by macona View Post
        The cog and stall is from single phasing. You might have a bad contactor.
        That's what I thought, but wouldn't I see low or no voltage between one phase and the other two at the motor in that case?

        I'll try swapping leads around to shift the wild leg, too.

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        • #5
          Even if it did start the wrong way on single phase, somehow, when/if the 3 phase comes back, it ought to actually stop and go the right way (plug reverse). The 3 phase has a definite direction and cannot reverse without the wires being changed.

          odds are it is starting and running on single phase for some reason. That has no definite direction.
          CNC machines only go through the motions.

          Ideas expressed may be mine, or from anyone else in the universe.
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          Generalizations are understood to be "often" true, but not true in every case.

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          • #6
            for the cost of a $2.99 can of electrical contact cleaner I would hose out the motor armature in a New York minute

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            • #7
              Well, I fixed it - purely user stupidity.

              When I got it home I had removed the coolant pump; of course, this was wired to the contactor, and I didn't tighten the screws back up when I removed it. Evidently the contactor wasn't making reliable contact with these screws loose. Diagnosed it by turning it on with the cover open - when it started the contactor didn't look off, but when it hesitated it arced like crazy.

              Tightened up those screws and all is well.

              Thanks for the help all!

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