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Variable freq drive locks up on Bport mill

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  • Variable freq drive locks up on Bport mill

    When I switch my Bport on and off at the mill, sometimes the variable freq drive will lock up. If I use the vfd to turn off and on, I don't have a problem. Is this normal or is my bargain drive a lemon?

  • #2
    I don't know about your VFD, but I would suspect that it is normal. Most have built in overcurrent devices, and inrush current from starting motor may be enough to trip it. I would recommend using VFD as primary control for the motor, switch as backup or safety device. That way you can also take advantage of soft start and braking which most VFD's provide.
    Jim H.


    • #3
      It's normal, or at least expected. You're supposed to do all switching with the VFD. Don't switch the motor separately.

      Try to make a living, not a killing. -- Utah Phillips
      Don't believe everything you know. -- Bumper sticker
      Everybody is ignorant, only on different subjects. -- Will Rogers
      There are lots of people who mistake their imagination for their memory. - Josh Billings
      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
      Don't own anything you have to feed or paint. - Hood River Blackie


      • #4
        Mikem, my vfd does the same thing, just the nature of the beast I guess. I was going to remove the old switch as it no longer seemed needed. Glad I didn't. A friend with years of B'port experiance was using my mill and got in to a hot corner. Instinctively, he reached up and shut off the switch just in time. The old switch is a good safety feature and where most people expect to find it. Even when a person gets used to a "new" position for a control, in an emergency they are very apt to reach for where it "always was".
        Good luck


        • #5
          It is not a good idea to switch the output of a VFD- all of them I have installled have strong words in the directions to never switch them. The VFD must ramp the current and frequency both up and down to work properly. A manual switch downstream from the VFD could ruin the VFD, and is surely against the directions and warranty terms.
          ron ginger


          • #6
            The VFD uses the motor windings as the inductor in the output (other similar "switching-type" devices have to put in a separate one).
            When you break the current in an inductor, it causes a voltage spike proportional to how fast you break the current.
            With no othre filter in series, the spike from the motor windings will arc across the switch and be applied directly to the VFD output.

            Therefore, if you do this to a VFD, you will be hitting the output with a several hundred or even maybe a several thousand volt spike. While there is protection inherent in some types, and added to others, it still isn't good for the VFD output devices. Eventually you will hit it just right and kill something.

            I would NOT let that stop me from hitting the emergency stop if I really needed it, though. VFDs can be replaced.


            • #7
              Anybody know anything about a Parametric's
              model 6020,I picked one up used but I can't
              get it going. I has a built in shear pin and
              I belive this may be the problem but don't
              know. Bob G.
              Bob Indiana