Any test for star or delta connection

Discussion in 'General Electronics Chat' started by dgalbraith, May 3, 2016.

  1. dgalbraith

    Thread Starter New Member

    May 3, 2016
    6
    0
    Can anyone tell me of a simple test to find whether a 3 phase generator (motor) is connected in star or delta?
    I have access to the 3 connections to it but not the motor itself as it is in a windmill and it is at the top of a 15m high pole.
    I am asking as the windmill in question does not produce as much power as another next to it.
    Both 6 kW windmills are controlled by inverters which I think only monitor the rectified DC voltage (~400V) output from the windmill so their output power will be very different depending on their connection type (star or delta).
     
  2. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    When you say STAR, are you referring to a Wye wound stator? If so, then there will be four connections. Three of them will have a single wire and the fourth will be a common connecting the other end of each coil to a common point.
    A delta on the other hand will have three connections, each one with two wires attached to each point.
    There can be other variations, but these two are most common. I am sure someone more knowledgeable will eventually chime in, but this is what I can offer for starters.
     
  3. dgalbraith

    Thread Starter New Member

    May 3, 2016
    6
    0
    Thanks. Yes, I'm referring to a Wye wound stator. It is possible that there are four connections at the stator where one of them is the common point connecting one end of all the coils together but I can't physically reach or see that point.
    At the point I have access to there are only the three wires. I was hoping I could do some sort of electrical test but I didn't know what.
     
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    5,003
    745
    If there are only three wires, then its wired in Delta,.
     
  5. dgalbraith

    Thread Starter New Member

    May 3, 2016
    6
    0
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    Does it matter? You get 400V between the phases either way.
     
  7. dgalbraith

    Thread Starter New Member

    May 3, 2016
    6
    0
    Yes, please see my first post.
     
  8. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    I don´t understand. All you have coming out of the black box generator are three phase wires, right?
    Then there is no way of telling if the generator is inside wired in wye or delta, beacuse from the view of the outside world they behave exactly the same. That means your inverter cannot see any difference either (unless one of them has the neutral connected to the generator and the other does not, which changes the whole situation).
     
  9. dgalbraith

    Thread Starter New Member

    May 3, 2016
    6
    0
    Yes, thats right.
    [QUOTE="Then there is no way of telling if the generator is inside wired in wye or delta, beacuse from the view of the outside world they behave exactly the same. That means your inverter cannot see any difference either (unless one of them has the neutral connected to the generator and the other does not, which changes the whole situation).[/QUOTE]
    No, there is no neutral.
    I think that answers my question though. Thank you.
    There is no test as from the outside they behave the same.
     
  10. BR-549

    Well-Known Member

    Sep 22, 2013
    2,004
    394
    I never gave it much thought.

    Would they behave the same with a load imbalance?
     
  11. BR-549

    Well-Known Member

    Sep 22, 2013
    2,004
    394
    Is there a ground wire on the windmill structure? Do you get any continuity between the three un-connected output lines and that ground? Windmill locked. Is there any static reduction apparatus using that ground? If yes and using same ground as possible Y connection, you could conceivably get noise on your output.
     
  12. dgalbraith

    Thread Starter New Member

    May 3, 2016
    6
    0
    Yes, the windmill is grounded. No continuity between any of the 3 output lines and ground. I'm not aware of any static reduction apparatus but there could be something in the windmill head.
     
  13. BR-549

    Well-Known Member

    Sep 22, 2013
    2,004
    394
    I'm not a motor theory expert....I would think no difference in configuration for power generation and load, unless of load imbalance or multiple imbalances.

    Maybe for reliability and survivability at generator site? Perhaps more current balance on windings? Who here can tell us when we get current on the neutral with Y? At generator.

    If the generators are different, there probably is other differences too. Blade input. Gearing. And control circuitry. All could have different setpoints, or change control at different times or rates.

    I have not looked into it, but there should be a way to actively test and dead configuration to tell.

    We would need in introduce an imbalance in 1 phase, and then measure how hard it is to prevent the other two phases from equalizing in out.

    Let's say that another way. On a D, whatever we throw in has got to come back out. On a Y, it doesn't. There's a hole in the bucket.

    Does this make sense to anybody?

    I would say yours is D.
     
  14. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    Not sure if I am understanding what you are asking, but I will off this. In an alternator with a Y winding, each leg will only have a single wire going to a connection point. The fourth connection or neutral, will have three wires connected and a fourth if it is used as a voltage source. If this is the case, that voltage would be 1/2 of the output voltage. So for example, an alternator that puts out 14volts, would see 7 volts at the neutral connection.
    On a Delta wound stator, each of the three connections will have two wires going into the connection, one from each phase.
    A wye wound has great charging characteristics at low speeds, wheras a delta has great output characteristics at high speeds. A combination wye/delta stator gives you the best of both worlds.
     
  15. BR-549

    Well-Known Member

    Sep 22, 2013
    2,004
    394
    I did not know that. I assumed the neutral was tied to ground. And that's the first I heard of a neutral as a voltage source.

    So does that mean if you use Y source and Y motor with neutral.......the neutral has to be isolated?

    I thought that the voltage at the junction was zero...even though there was current. And that's why you could tie it to ground.

    I remembered that Y has higher voltage but D has more current but all have same power.

    I'll have to re-study the neutral. Thank you.
     
  16. Andrew Hodson

    New Member

    May 26, 2016
    5
    1
    Was thinking about this in bed, If 3 point @ 3 voltages, then if = star then 1 coil'll try & comdect if both directouns? Need to sleep on it again!l
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,566
    2,379
    You have to get out more!;)
    Max.
     
  18. bwilliams60

    Active Member

    Nov 18, 2012
    725
    90
    I'm confused. Good point Max :)
     
Loading...