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Thread: 120v from 3 Phase 240v

  1. #1

    120v from 3 Phase 240v

    Anyone have experience taking 120v power from a 3 phase 240v CNC machine?

    I know you are not supposed to use the ground as a neutral, but unclear on my options. I’m trying to power the spindle chiller (120v) from the machine.

    I can get the 120v I need through one of the hot legs and ground.

    Thanks

  2. #2
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    Simplest solution would be to use a 240 to 120V transformer off of 2 of the legs.

    I don't think there's any guarantee that the nodes of your 3-phase power are equidistant from ground.

  3. #3
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    Quote Originally Posted by Greg Funk View Post
    Simplest solution would be to use a 240 to 120V transformer off of 2 of the legs.

    I don't think there's any guarantee that the nodes of your 3-phase power are equidistant from ground.
    ^^^^ This

  4. #4
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    Quote Originally Posted by Greg Funk View Post
    Simplest solution would be to use a 240 to 120V transformer off of 2 of the legs.

    I don't think there's any guarantee that the nodes of your 3-phase power are equidistant from ground.
    + 1 to this advice
    Gary Campbell
    CNC Replacement & Upgrade Controllers
    Custom 9012 Centroid ATC

  5. #5
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    I added a 240-208 transformer for a CNC. Seems to me there was a wiring option that created a neutral on the output side for 120? Is that correct? Still kinda baffles me how that would work.

  6. #6
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    Never tap one leg to ground off 3 phase, only use a neutral wire.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  7. #7
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    Quote Originally Posted by Bill George View Post
    Never tap one leg to ground off 3 phase, only use a neutral wire.
    240V service typically doesn't have a neutral.

  8. #8
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    Quote Originally Posted by Greg Funk View Post
    240V service typically doesn't have a neutral.
    The 208 ones do, people get confused 208-230 3 phase etc, all a big mystery. In any event using the ground as neutral is not allowed nor safe.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  9. #9
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    Quote Originally Posted by Bill George View Post
    The 208 ones do, people get confused 208-230 3 phase etc, all a big mystery. In any event using the ground as neutral is not allowed nor safe.
    208V 3-phase is normally a Y configuration with a neutral. 240V is normally a Delta with no neutral. Agree about not using ground for neutral.

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