Two legs of three phase power supply
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  1. #1
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    Default Two legs of three phase power supply

    Hello guys,

    I am new to this forum. I have been reading about this but need to confirm my understanding on this subject about three phase power. For small load, is it generally okay to use two of the three legs of a three phase power supply?

    I am trying to power a single phase 24VDC,60W power supply:
    - Input Voltage: 100-240V;
    - Output Voltage: 24 Vdc
    - Rated Operational Current: 1.1A input, 2.5A output, 30A inrush, 3.75A surge

    The incoming power line is three phase 230V

    Is this okay by code?

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    Pretty common to do that for small loads on a machine.

    ALL power is tapped off 3 phase, so, yes. If you have several such separate loads, it is best to use different wire pairs (phases) for different loads, but for small loads it is not a big deal.

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    Is it three phase 230V line to line, or three phase 230V line to neutral?

    If the latter, then the line to line voltage will be 400V which is too much for your supply - you need either a 400V input power supply, or to connect it line to neutral. This is common in most areas outside north america and japan.

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    Quote Originally Posted by SomeoneSomewhere View Post
    Is it three phase 230V line to line, or three phase 230V line to neutral?

    If the latter, then the line to line voltage will be 400V which is too much for your supply - you need either a 400V input power supply, or to connect it line to neutral. This is common in most areas outside north america and japan.
    It isn't really all that different NA or Japan, either.

    Canada, arguably more "industrialized" (vs "service industry") per capita than the South 48 off the back of a much smaller population but heavy mining, petro, minerals extraction and timbering, more high-tech than just a little bit, simply brings the next step-higher a tad closer to the end Luser.

    Japan is so densely populated, everything is "close" where industry exists at all.

    They just happen to have roughly half and half 60 Hz and 50 Hz grid coverage. Which SEEMS to run odd Voltages, but "not so much" in reality.

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    Each leg of your service is rated for 108V to 120V, it appears that you could power your inverter off a single leg and a neutral. Tapping two different legs and the neutral will give you the 240 single phase you asked about.

    Oooops, I just re-read the OP, 30 amps input, yea you might want to stick with the 240 single phase on a 40 amp breaker.

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    30A inrush isn't super uncommon. Many LED drivers will draw that if you give them enough fault current to play with. Capacitor charging is brutal.

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