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3 phase in a home shop

Discussion in 'The Repair Shop' started by Homemade, Jan 22, 2018.

  1. Al Smith

    Al Smith Pinnacle OPE Member

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    The easiest thing to do for three phase is either buy or built a rotary phase converter .It's relatively simple ,you can google it .I lost count of how many I've built for other people .
    In my shop I have a 5HP converter .240 single in,480 3 phase out ,also transformed to 240 three phase with a single phase auto transformer to get approx 265 single which will fire 277 volt lighting .
    If you build a converter right it will run with approx 92 percent efficiency rating .Which if compared to single phase motors about on a par or maybe even a little better .Properly built they will start up to the rating of the motor used to build the converter with a combined load of up to three times that amount providing the largest motor does not exceed the size of the converter . Nothing magical about it,it's just an induction generator in another form .
     
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  2. RD35

    RD35 Well-Known OPE Member

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    Just skimmed through these posts. I am a little concerned about all the "wild leg"/"high leg" discussion. Not sure this ever got totally cleared up. The most common type of shop 3-phase for small shops and for commercial buildings is a 120/208V "wye" connected system. This system gives you 3 phases that all measure 208V from leg to leg and all measure 120V to ground. There is no "high leg" on this system. The high leg is present on a 240V center-tap delta system that has a center tapped transformer for 120V. So you have three 240V transformers connected leg-to-leg and one of them is a standard center-tapped Single Phase transformer like the ones used for homes.
    So, if you are wanting to run a 120/208V 3-phase 4-wire system in your shop (wye connected) then you will not have a high leg to worry about. As mentioned earlier, you need to consult a qualified electrician who can survey your needs and then contact the utility provider to determine what is available from them at your location.
    Lastly, I would also recommend you check the rates that are charged for 3-phase power. It was mentioned in the opening post that 3-phase equipment pulls less amps. This is true....but it does not always pull less watts. The power company charges for wattage, not amperage. So by going to 3-phase your kilowatt-hour usage will not change (much anyway...maybe just a little less due to better efficiencies, but not much). So, the power usage rate ($/KW-H) is what I would look at as well as the minimum charges and install fees. Unless you are running a large shop with lots of 3-phase equipment, you may just want to consider a phase converter that creates 3-phase power from your single phase service like Al Smith suggested above.
    Just food for thought. Hope this info is helpful.
     
  3. paragonbuilder

    paragonbuilder Jon1212 Approved!

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    Good post!
     
  4. Blackgreyhounds

    Blackgreyhounds Super OPE Member

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    Good post!
    FWIW, I have a home-brew rotary 3-phase converter to run an old jointer down in my woodworking shop. I bought it with the machine and had an electrician install it. Even though a converter is not perfectly ideal, it is very convenient to have the option of 3-phase service in addition to standard single-phase 120/240V when/if you are looking purchase used machinery. As @Al Smith said, for a small, home shop, it's definitely easiest and cheapest to buy/make a converter.
     
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  5. OldJack

    OldJack Well-Known OPE Member

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  6. Leafy

    Leafy Well-Known OPE Member

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    I wouldn't be so sure, last time I priced it out it was cheaper to buy a vfd than a rotary converter, at least in bridgeport and reasonable engine lathe sizes. The vfd are great if you are trying to run just 1 motor but they don't seem to like it when the load varies itself a lot, like if you tried to use it as the input power for a whole cnc. I'd like to get 3 phase at my next house but at least around here they won't wire it to residential zoned houses, need to find a house that's in a dual zoned residential and industrial or commercial.
     
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  7. Al Smith

    Al Smith Pinnacle OPE Member

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    There's other options too depending on what you want to do .A static converter ,more or less just a start circuit for a 3 phase motor is rather cheap and is really easy to build .The short side is you only get about 60 percent of the power because one leg is missing but they work .Regarding CNC stuff ,you won't find many home shops where anybody has that stuff .I have however seen small commercial shops run them on a rotary converter .
    I think way too many people take this stuff as if it were rocket science which it's not . However somebody like myself who knows it has a hard time explaining it .Counting my navy time I figure I've been doing this stuff for 51 years .My pension from the IBEW is based on 45 years of service which will start August 1 of this year .Time to pass the torch .
     
  8. T.Roller

    T.Roller Huffy and Puffy, Roll Tighter Tater....

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    Congrats on the retirement brother. IBEW local 175 here.
     
  9. Al Smith

    Al Smith Pinnacle OPE Member

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    IBEW #32 Lima Ohio ,about 19 years .Ford Lima Engine plant UAW #1219 28.9 years .
     
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  10. Fresch

    Fresch Well-Known OPE Member

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    I.B.E.W. lu#43 Syracuse N.Y. been retired one year, missed our $increase by 3 months . We have enough to make it to, past my death unless sword hits the fword.
     
  11. Al Smith

    Al Smith Pinnacle OPE Member

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    I think it might be note worthy to mention another one of my mad scientist stuff . I was given a 400 amp transformer DC welder .It was originally wired open delta mean using three phase through two transformers .I rewired it single phase and used a double Pi filter to remove the single phase ripple .I figured as it is it's about 200 amp which is plenty for what I do .It will run 5/32 " iron powder rods or 3/16" fast freeze rods like a 6010 which is plenty for what I do and is smooth as silk,very little if any ripple .
    So stuff like this is not something taught in apprenticeship classes but never the less unconventional or not does work .
     
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  12. Junior Samples

    Junior Samples Super OPE Member

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    I haven't worked in this for about twenty years but most utility companies were fazing out the Delta services and all going Y services for new construction. Lord I know there are alot of old services out there still.
     
  13. Al Smith

    Al Smith Pinnacle OPE Member

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    I've seen some really odd set ups .Try 480 delta corner ground. 480 delta through a "zig-Zag" transformer set up to get an impedance connected neutral for 277 volt lighting .
    My 200 amp single phase service at my shop comes in at around 246-248 .Using a 240 to 24 volt transformer hooked as an auto transformer for boost I can get close to 270 which will fire 277 volt lighting .
     
  14. Al Smith

    Al Smith Pinnacle OPE Member

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    I could ramble on for hours about this stuff .However to the topic as I said before a rotary phase converter if built correctly has around a 92 percent power factor .This surpasses most single phase motors if converted to three phase .It's not magic ,just a simple application of physics that have been around since Ben Franklin flew his kite and shocked the pee out of his assistant .Ben had an ornery streak . Actually more than likely Tesla figured it out .He was smart enough not to fly a kite .
     
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