How to rewire a 3 phase motor for low voltage (230V)

Discussion in 'ELECTRICAL ISSUES - POWER YOUR MACHINES & SHOP' started by Nels, Feb 28, 2011.

  1. Nels

    Nels Founder Staff Member Administrator Supporter

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    Sometimes, you apparently need to rewire a 3 phase motor for low voltage (230V as opposed to 460V) in order to connect the motor to a VFD. This apparently involves the windings and associated wire configuration.

    How is this done?
    I am lost, and have never touched motor windings before.

    Thanks,

    Nelson
     
  2. Tony Wells

    Tony Wells Administrator Staff Member Administrator

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    Maybe this will help, Nelson.
    [​IMG]
     
  3. Tony Wells

    Tony Wells Administrator Staff Member Administrator

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    Yep Turbo, that's exactly what that is. It was the simplest way to provide the basic information. I've wired more than a few myself. Always the plate rules though. I've seen rewinders come back with some weird variants that they failed to document. Had to call them up to get the real story.

    Everybody should have a yellow UGLY book. ;)
     
  4. Nels

    Nels Founder Staff Member Administrator Supporter

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    Another stupid newbie question- you manually relocate the brass windings? What happens if the brass wire breaks (anticipating all-thumbz at it again)- do you need to buy magnetic wire of the correct gauge to replace it?

    I sure could use a video showing someone doing this- there was one on Youtube-
    in which an old motor is repaired, but it wasn't very clear.

    The reason I raise this is because there is a Youtube video, actually, a set of 5, by a user called "CVMikeRay" about hooking a VFD to his 13" South Bend, and the first step he does is to rewire his motor to "low voltage" (230) as opposed to 460. He lost me right away as to (a) why he would need to do that, and (b) exactly how he did it.

    Thanks.

    Nelson
     
  5. Tony Wells

    Tony Wells Administrator Staff Member Administrator

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    I know of no brass wiring in the "peckerhead" as we say in the south. There should be 9 insulated wires coming out of the windings into the connection or termination box. Those are numbered, usually with poultry rings or some such. They will be paired up according to one of the diagrams above. You should make sure you can read all the numbers before you disconnect anything. That will tell you for sure what voltage it is currently set up for and whether delta or star. The windings themselves are enameled magnet wire, but you won't normally need to mess with them directly, only the insulated pigtails in the box.
     
  6. Nels

    Nels Founder Staff Member Administrator Supporter

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    Ah, I understand. I have seen those. Sometimes on old machines not in good shape. Then I would need to know how to test to find out what goes where.

    What is delta and star?

    Thanks,

    Nelson
     
  7. Tony Wells

    Tony Wells Administrator Staff Member Administrator

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    Delta and star (or wye) is the method of connecting the windings of the motor. It has to be compatible with the phase relationship of the supply. In a VFD change, don't worry about it, just go with the way it is currently. It would only matter if you were moving to an area of the world or country that had a different scheme than home. Sorting out unmarked pigtails is not simple. A motor shop may need to get involved then.
     
  8. Lost Pup

    Lost Pup Guest

    Question?

    With a dual voltage 3 phase motor do you wire it to 240 or 480 ?

    I have a Teco Jnev 101 to connect to a dual voltage Baldor 3 phase motor. Is there a benefit to either high or low if the VFD will operate it?

    The Baldor is setup to the high voltage out of box.
    Thanks
     
  9. Tony Wells

    Tony Wells Administrator Staff Member Administrator

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    A quick look at that VFD unit tells me it should not handle anything but 110 motors, so I'm not sure it will run a 240/480 motor.
     

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