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Thread: Need 3 phase Assistance

  1. #1
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    Need 3 phase Assistance

    As I am doing research into wiring 3 phase circuits, I keep coming up short. I mean, things are still a little hazy, and I would love help nailing down the details.

    1.) Assuming I am using 10 gauge wire, do I need 3 conductors and a ground, or do I also need a neutral? For some reason I seem to be getting mixed messages in this department.

    2.) What's the least expensive way to get power to the four 3 phase tools. Meaning, how do I connect four loads to the one power source with the least expense? Do I need a 3 phase load center (breaker box), or do i just run all the tools into one junction box and feed it directly from the converter?

    3.) Do you have any pictures of your 3 phase wiring/circuits?

    Thanks for any help you can give!

    Hutch

  2. #2
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    Quote Originally Posted by Matt Hutchinson View Post
    1.) Assuming I am using 10 gauge wire, do I need 3 conductors and a ground, or do I also need a neutral? For some reason I seem to be getting mixed messages in this department.
    you will need 4 conductors

    Quote Originally Posted by Matt Hutchinson View Post
    2.) What's the least expensive way to get power to the four 3 phase tools. Meaning, how do I connect four loads to the one power source with the least expense? Do I need a 3 phase load center (breaker box), or do i just run all the tools into one junction box and feed it directly from the converter?
    If you are running multiple circuit each one should have it's own branch circuit protection. If you will not be running all the loads at the same time you can put a seperate plug on each one and plug it into the source.

    Fell free to ask as many questions as you need since we don't want anyone getting hurt.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
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  3. #3
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    Ok.....

    So, being a novice, can you clarify the wire type? Do I need 10/3 with ground, or something else?

    Also, I really don't need the tools on separate circuits at this point. Running the receptacles in series should be adequate, right? (I don't plan on running more than two tools at once, and even that's not likely.) With that said, since a breaker is protecting the phase converter, could I run the circuit from the converter to the tools with no disconnect in between?

    Thanks!

    Hutch

  4. #4
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    10/3 w/ ground is fine. I remember a discussion on another board about running 4 recepticles off 1 breaker which caused me to break out my NEC book. you'll be fine running 4 recepticles off of 1 breaker. The rule for running seperate circuit only applies for hard wired loads. The circuit braker is fine, no additional disconnect is necessary.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  5. #5
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    Nice!

    Thanks Don! I really appreciate the info!

    SO here's another question. The idler motor for the converter is 10 hp. If the converter is on a 60A breaker, if a tool's motor is overloaded is it possible for the breaker not to trip? I mean, the combined amperage of the idler and machine (even a machine under load) will not be anywhere near 60 amps. But is this 'not properly tripping' idea faulty since the breaker is back on the single phase side (where the amperage has to be multiplied.)?

    Hutch
    Last edited by Matt Hutchinson; 06-30-2009 at 03:00 AM.

  6. #6
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    matt,
    wire size is determined by amp draw, 10ga wire is suitable for 30amps.
    30 amps of 220 3-phase (low voltage) is about a 10hp motor.
    3-phase motors will run just fine without a ground but it is a very good idea to install one for safetys sake. also if there are any single phase controlls on your equipment (most have) they will make use of the ground wire to complete their circuit.
    i do not use a convertor so can`t offer advice on building one.
    if you are using 10ga wire leaving the convertor you should install a breaker no larger than 30amp between the convertor and the 10ga wire.
    breakers are designed to protect wire not motors.
    if you want to add motor protection it is best to fuse each line at the controlls.
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  7. #7
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    Quote Originally Posted by tod evans View Post
    .....breakers are designed to protect wire not motors.
    You can not hear that enough. Had this very conversation with clients yesterday about a fuse panel that the fuses (not breakers) had been replaced and with to large a fuse.

    I think I have plans for a 10hp phase convertor. If you scrounge parts it will cost you about $250 to build but it is one of the best designs out there. A friend of mine has been developing it over 10+ years and while not cheap, I really believe his are the best out there. Bruce is always willing to help someone new build one, he lives for this stuff.

    You hit a button, it starts and works with no drama! I am very impressed with mine.
    God grant me the senility to forget the people I never liked anyway,
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    and the eyesight to tell the difference.


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  8. #8
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    Hm

    Thanks for the clarification. I guess I wasn't really thinking quite right about circuits, even though I actually did know that breakers are for protecting wiring. How quickly I forget.....and that's why I post electrical questions on forums.

    Do you think it's necessary to protect the motor?

    As for the converter, I have already purchased one. Spent about $300 for the converter box, but I still need a 10 hp motor for it. Too bad I didn't post something before I bought it!

    Also, I don't think there are single phase controls on my machines, but I will have to double check that. The machines I will be running are an 8" jointer, a 3hp Rockwell Unisaw, a 5hp 14" Rockwell RAS, and eventually I will be upgrading the drive system on my big lathe to a 3hp 1100 rpm motor with a VFD.

    Anywho, thanks for straightening me out!

    Hutch

  9. #9
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    There are Circuit breaker designed for motor protection. The are labeled MCP for Motor Circuit protectors. I prefer them to fuses since not only do they protect the motor froom overload but they also offer protection from single phasing in the event 1 fuse blows. leaving to 2 hot legs to the motor. For three phase circuits on 220/230 volts you can figure the FLA as 2.3 amps per horsepower.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  10. #10
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    Cool!

    Good stuff! Thanks Don, that really helps to narrow things down. When I have tried to do searches on industrial supply websites I get overwhelmed and confused cuz I have no idea what half the stuff is for.

    Hutch

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