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RPC Electical problem

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  • RPC Electical problem

    Ok I am going to cover what I have. Most of you probably remember what I have but...

    Lathe: 2 speed motor 3phase 3hp and 1.5hp
    Phase-A-Matic phase converter (no run caps)
    Idler Motor: 5ph 3phase

    My problem. When I try running my lathe in the "High Speed" setting, it either flips the fuse or it has cause another fuse for a different part of the house to flip. I tried running the lathe at the lowest RPM (81) of the "high speed" setting and that is when it flipped a fuse for another part of the house but not the lathe. It does NOT cause any troubles when the lathe is run in its "low speed" setting.

    My fuse is a 30amps at the box for the lathe which is running 220 directly to the lathe with nothing in between.

    What am I missing?

    Thank you all for you help in the past and for the future!!

  • #2
    What size wiring from the fuse panel to the convertor?

    Also, I have had problems with fuses and rotary convertors. Mine will blow a 30amp fuse just by switching the convertor in.

    The entire circuit is protected by a 50amp breaker and my wire is #6.

    I have even used slow blow fuses still no good. I dont have any shorts, it may just be an inrush from the caps (for mine). JRouche


    • #3
      I ran 8 or 10ga.

      I had a problem with the fuse popping when I flipped the switch too, till I started spinning the idler motor before i flipped the power swithed. That solved that problem.

      I used slow to blow buss fuses also, but replaced the start box with a 60amp switch box with no fuses. If I didnt get my idler motor spinning fast enough before I flipped the power switch, it would blow the slow fuse. Was tired of spending a buck a fuse.


      • #4

        are you saying you are starting the 5HP motor with start caps and then run it with no run caps? if so, this could cause a current and voltage imbalance that could definitely blow fuses. i start my 5HP idler, and then fire up the 5HP motor on the shaper (and everything "grunts" for a few seconds) and i have never blown one of my 20A fuses. i think all my wiring is 8 ga.

        andy b.
        The danger is not that computers will come to think like men - but that men will come to think like computers. - some guy on another forum not dedicated to machining


        • #5

          I dont have run caps. Peter on the the PM website said run caps should fix the problem.

          I will be ordering some and figuering out where to put them.


          • #6
            Cuemnaker, if your blowing fuses on a branch circuit that your lathe is not connected to you have another serious problem. I would call an electrician to trace all your circuits. Uncrichie