3 phase motor with 3 leads - testing if star or delta

Discussion in 'General Electronics Chat' started by Robin Stokes, Feb 16, 2016.

  1. Robin Stokes

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    Hi all,
    this is probably a very basic question for most of you...
    I have an old but good quality drill press with 3 phase motor but only have single phase supply.
    The motor is a Newsome 1/2 hp 415v motor with only 3 connection points... so the circuits are completed internally. If it is possible I would like to test the windings to see whether it is wired star or delta as I have read it could be either & there is no indication on the motor spec plate. Obviously I can't simply plug it in. Can anyone say what I must do? I have a multi-meter but no other electrical test gear. Shocking I know! :)
    I have no problem dismantling the motor if necessary.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,974
    744
    Usually motors have six terminals and using connector straps makes them Star or Delta, if yours has only three terminals sounds like its in delta.

    Do you want to run it on a single phase supply, if so use VFD inverter.
     
  3. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,034
    1,632
    Initially I would say Delta also but being 415 volt that has me thinking Wye being widing a small motor like that for 415 volt in a delta configuration would be a total PITA.

    Good chance if you poop an end bell off you will find a center point connection where all three windings come together.
     
  4. Robin Stokes

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    Thanks, it is on a late '60's drill (may not be original of course) does only have three leads/connections. If it were 6 lead then I could easily convert it as reqd. I don't want to ruin a working motor by guessing it is in delta & being wrong! Is it common for a 3 wire motor to be in delta? I was worried that star would be more likely - not that I have any expertise... I am hoping it will be delta then I can use capacitor start / capacitor run set-up as others have done - it is way cheaper than an inverter! Will only be intermittent use. I'm aware that correct capacitor rating & voltage is important.
     
    Last edited: Feb 16, 2016
  5. Robin Stokes

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    Thanks, wish I'd checked when I stripped it down previously! All 3 windings connected together would be star?
     
  6. Robin Stokes

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    accidental re-post!
     
    Last edited: Feb 16, 2016
  7. bwilliams60

    Active Member

    Nov 18, 2012
    722
    88
    A wye wound stator will usually have three single wire connection points plus a neutral junction connection. A Delta stator will have three double wire connections with no neutral connection. Draw them out. you will see what I meam.
     
  8. Hagen

    Active Member

    May 8, 2010
    30
    1
    It sounds like you want to run this motor on single phase using a version of a static phase converter, which normally consists of a starting (electrolytic) capacitor, which is cut out of the circuit when the motor is up to speed, and an oil filled running capacitor which is not cut out. If this is the case, it doesn't matter if the motor is connected star or delta, though a small 415 volt motor is probably connected star (wye). Do you have a transformer to supply the 415 volt single phase supply?
     
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