3 phase electrical equipment

Discussion in 'Shop Talk' started by Gideon's War, Jun 7, 2006.

  1. Gideon's War

    Gideon's War Well-Known Member

    Dec 18, 2005
    In a state of Grace by the Lord Jesus
    I had a friend who went to an auction and saw a bunch of equipment (food type stuff) that was 3 phase. What is the difference between 3 phase and "regular" (other than the 2 additional phases :) ? Is it hugely more expense to get the utility to run the new juice or what else could I do to use this equipment?
  2. TheBlueOne

    TheBlueOne Well-Known Member

    Jul 2, 2004
    Look up at the power poles in your area and count the wires. You need (4) in order to have three phase and everywhere there is a drop to a customer there are (3) transformers. Outside of a residence there is (1) transformer. To upgrade from single phase to three phase (if they will even do it) will be HUGELY expensive. It is almost never done on a residence because the cost can never be recovered in electricity sales, and rarely done on farms.
    The alternative is to purchase and use a phase converter. These are common on farms in the country that are far from industrial power. They start around $1000 and go up from there depending on size and duty cycle. Typically when running a phase converter an upgraded single phase electrical service is required due to the current draw.

  3. agmantoo

    agmantoo agmantoo Supporter

    May 22, 2003
    Zone 7
    If you want to do some "engineering" and are willing to spend a few bucks I can at a later time give instructions on how to make a "mickey mouse" 3rd leg of power. You have 2 legs of the 3 phase now. It is from the 2 legs that the 240 volts is available. I use such a means to drive a 5HP cutoff grinder and it works fine for the task.
  4. rambler

    rambler Well-Known Member Supporter

    Jan 20, 2004
    Good advise so far.

    Unless you are somehow very lucky, will be hugely expensive to get 3-phase run to your place. Hugely.

    Phase converters are available, but they draw some power, and cost a bit to get.

    The phase converter is basically an idling 3phase motor running off the 220 you have, so you can build your own - if you know what you are doing. Need to match loads somewhat, & so on.

    The advatage to industry of a 3phase setup is that the motors are much smaller, & cheaper, and slightly more efficient & wiring to them is much smaller. Much cheaper if you have 100 motors in your business.

    The disadvantage is that start-up cost of having to install a 3-phase service. If the other 2 businesses on your block already have it, only costs 'a lot' to get your building wired too. If you are a quarter mile - or 5 miles - from the nearest 3 phase - it costs hugely. They need to hang 3 transformers for you, and more wire, and they need to come from a 3 phase source. They will expect you to meet a minimal use for all that, and so on.

    You lose many of the efficiency benifits when you run your own phase converter.

    For a couple small motors, might be cheaper to swap out for single phase 110 or 220 motors if you aren't into building your own converter.

  5. luckypabst

    luckypabst Active Member

    Oct 16, 2004
    Lone Pine, CA
    Yea, Rotary phase converters are pricey. Depending on the load, you can get a static phase converter for not a lot, certainly less than the rotary "motor" style.

    Variable frequency drives are the latest thing but I think they're best suited to machinery that sees a lot of RPM change.

    Check Enco for generally low prices, here's an example:
    static phase converter
  6. farminghandyman

    farminghandyman Well-Known Member Supporter

    Mar 4, 2005
    some depends on the voltage, if the voltage is 240 or 208, you can use a converter, if it is 440 or other that will create More problems

    I have used static converters, they use capacitors to excite the third leg and the motor them runs on two windings,

    I at one time ran my walk in cooler on a rotary converter,
    this can be done two ways, leave the converter run continuously, or to set up a delay on the compressor and when the thermostat call for cooling it starts the rotary converter and then after the converter gets running it kicks in the compressor, (compressors need the rotary converter) in that it actually powers the third winding, a static converter doesn't,

    for full power you need the rotary coveter, the static will only produce two thirds of the power.

    on my farm the "three phase" power is what is called open delta three phase, It uses a conventional single phase transformer and off of it I get the standard single phase, 120/120 240 normal home power, but by running one additional transformer and one of the there phases, you have what is called open delta three phase, or some times called (wild leg three phase)(delta wired), and it will produce three phase, for the cooler and the freezer and the meat grinder, metal mill and lathes and air compressor,
    the three phase lines were with in 200 yards of the farm and the cost was all ready absorbed by my usage of power, (our electrical company raises the Min, for 5 years to pay for the equipment but if you use more power than the Min. fee, there is no additional charge other than the power cost), so it did not cost me hardly any thing, ( and i have an electrician friend give me used boxes, and breakers off of E bay, I think the cost to me was about $300, to have it installed and wired,
    normally the wiring using the boxes I used would have been in the thousands, as the one box was $1600 retail.

    MY guess is a rotary converter would be you best answer for part time needs, and let it run your three phase system if your just needing it a few times a year, if it is a saw or like a dedicated static phase converser would work OK,