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Single Phase or Three Phase Machinery

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  • 03-10-2009 4:40pm
    #1
    rexel1
    Closed Accounts Posts: 45 ✭


    I am setting up a woodwork workshop and am in the process of sourcing machines. I will be doing quite a bit of work. Should I go for single or three phase machines? Is three phase much more economical than using single phase machines?


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    #2
    Davy
    Moderators, Category Moderators, Business & Finance Moderators, Technology & Internet Moderators Posts: 19,340 CMod ✭✭✭✭Davy


    If you have a three phase supply already that's what i would be going for


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    #3
    rexel1
    Closed Accounts Posts: 45 ✭rexel1


    I have a single phase supply at the moment but can get a covertor at a good price so im not too worried about installation cost.

    Running costs are what im trying to campare. I would be running a large bandsaw, sander and dust extractors. Would a three phase electricity bill be much cheaper than running off a single phase.


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    #4
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,546 Mod ✭✭✭✭2011


    3 phase machinery is:

    1) More rubust.

    2) Cheaper to buy.

    3) More efficient.

    4) Cheaper to maintain because the construction is simplier with less to go wrong. It also runs smoother meaning less wear and tear on bearings, this is due to the "naturally occuring" rotating magnetic field produced by the stator windings.

    5) 3 phase machines are available with higher outputs than single phase machines.

    If you have the choice, 3 phase is the way to go! You also have dual voltage i.e. 400 or 230 volts.
    can get a covertor at a good price
    This is not a great way to get 3 phase power. Get a 3 phase supply from the ESB if you want 3 phase is my advice.

    If you decide to go down this road you will be limited to a maximum of about 15kVA due to the largest single phase supply available. If you go for a three phase supply a much large capacity supply can be made available (the sky is the limit). For a workshop this would be important, you dont want a situation that you can only operate so many machines at a given time without risking blowing the main fuse.

    I think that if you use an invertor connected to a single phase supply to feed almost any 3 phase machine that you will see all of the lights go dim. Also you may well blow your main fuse due to the high starting current of all 3 phases being fed from 1 phase!

    To know how large a load the invertor can supply first look at its rating. What is the invertor rated at in terms of VA??? This should be on the name plate.

    Be warned invertors can also cause problems with harmonics!


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    #5
    rexel1
    Closed Accounts Posts: 45 ✭rexel1


    Cheers,

    I do know our local esb lines were all changed in the last year and we have a stronger power supply because of it. Not sure what differnce it is in technical terms though. When the neighbours used to be welding all our lights dimmed but no problems since the lines changed.


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    #6
    Stoner
    Moderators, Home & Garden Moderators, Technology & Internet Moderators Posts: 10,952 Mod ✭✭✭✭Stoner


    with respect to almost any motor, there is little to compare to a three phase induction motor, so +1 for a three phase supply, anyway with a three phase supply you still have an option to use single phase supplies,


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    #7
    davelerave
    Closed Accounts Posts: 1,712 ✭✭✭davelerave


    Is 3-phase available locally?.A convertor plus suitable SP supply(prob >20kva ct metered)if available, is expensive.


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    #8
    Davy
    Moderators, Category Moderators, Business & Finance Moderators, Technology & Internet Moderators Posts: 19,340 CMod ✭✭✭✭Davy


    rexel1 wrote: »
    Cheers,

    I do know our local esb lines were all changed in the last year and we have a stronger power supply because of it. Not sure what differnce it is in technical terms though. When the neighbours used to be welding all our lights dimmed but no problems since the lines changed.

    If you take a pic overhead gear near you it should be easy to identify what's available.


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