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3 Motors And 1 Vfd

Discussion in 'Grinders' started by Bluefish, Nov 20, 2020.

  1. Bluefish

    Bluefish New Member

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    Not really sure where to post this question but it does deal with a grinder so here it is.

    I have 3 identical 3 phase motors the i plan on using, i'm good with getting the VFD for these motors but what i would like to do is run them off of only 1 vfd.

    My little brain says just put a 12 terminal 4 position switch in after the vfd and it should do what i'm after. here is the switch i'm looking at


    Anyone see any problem with this other that only having one control panel for all of these machines?
     
  2. dancom

    dancom Dust Maker Best Shop Tool

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    Unfortunately, that switch only contacts two poles at positions 1 through 3 and none for position 0. If you look at the contact table there are only two Xs per position. Would work ok for single phase but not three phase.

    You'll need a contact rating of about 15A (AC3 motor rating). I haven't found a decent three pole switch as of yet.

    What size are the motors? I can look around.

    Dan
     
  3. Bluefish

    Bluefish New Member

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    The motors are only 1hp 3.8A, I’d like 2 ph but I got these triplets
     
  4. dancom

    dancom Dust Maker Best Shop Tool

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    Some options:

    Use a single 4 wire receptacle, like a NEMA L14R-30 on the VFD side and have each motor with a mating 4 wire male connector. This requires that you unplug and plug to switch motors. Safe, cheap and effective, but time consuming and not very pretty.

    Another way to do it would be to buy three 3 pole toggle switches. One for motor 1, another for motor 2 and a third for motor 3. There is a risk that you could start more than one motor if you had more than one switch closed. No harm to the VFD, but safety-wise this is an issue.

    The right option, industrial, to use three 3 pole contactors in an enclosure, but by the time you get all the controls the price will be more than a new VFD. The auxiliary contacts would be wired to prevent two motors from being on at the same time.

    I will keep my eye out for a proper switch. The ABB - ONSO34PB Cam switch looks promising from a catalog perspective, finding one is another story.
     
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  5. Bluefish

    Bluefish New Member

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    so wire in 3 tpst switches and just using the one i need at a time. yes i can make that work, need to build a control panel for the vfd's removable faceplate anyway so can put those in with LED on lights. Thank you Dan
     
  6. dancom

    dancom Dust Maker Best Shop Tool

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  7. dancom

    dancom Dust Maker Best Shop Tool

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