Split phase supply

Discussion in 'Electricians' Talk' started by Bradley6969, Apr 15, 2019.

  1. Bradley6969

    Bradley6969 Member

    So I have split phase supply,
    L1-L2 0V
    L1-L3 450V
    L2-L3 450V
    L1-N 230V
    L2-N 230V
    L3-N 230V

    So looks like L1+L2 are together then L3, got some outgoing circuits from a panel fed with 4 core cable which has 4 pole RCD then couple of Double pole switches and single pole, can I connect this up as normal and balance loads everything should be ok?
    Thanks
     
  2. Bob Rathbone

    Bob Rathbone Well-Known Member

    No, you don't have a split or Bi phase supply, the readings given don't add up. For a split or bi phase supply the line voltage should be double the phase voltage as they will be 180 degrees out of phase. For a 3 phase supply the line voltage should be phase voltage X 1.732 (square root of 3) as they are 120 degrees out of phase. You have a supply fault, if these readings are at the intake, call the supplier.
     
  3. peter palmer

    peter palmer Well-Known Member

    Why is the phase to phase voltage 450 though and not 400? its a lot closer to twice the L-N voltage than a 3 phase value would be.
     
  4. Bradley6969

    Bradley6969 Member

    QUOTE="Bob Rathbone, post: 1701240, member: 55313"]No, you don't have a split or Bi phase supply, the readings given don't add up. For a split or bi phase supply the line voltage should be double the phase voltage as they will be 180 degrees out of phase. For a 3 phase supply the line voltage should be phase voltage X 1.732 (square root of 3) as they are 120 degrees out of phase. You have a supply fault, if these readings are at the intake, call the supplier.[/QUOTE]
    Why? There’s no potential between L1+L2 meaning there connected at the one end and line voltage was 240v and phase was between 460V and 483V
     
  5. MGW

    MGW Well-Known Member

    All the split phase supplies I have found in UK one can walk outside and see the transformer on a pole or the twin supply wires to the transformer and see it is a single phase split, I would say 450 volt line to line is rather high for three phase, but should have been 460 volt for split phase, however your clearly not measuring all phases at the same time so could fluctuate. However with L1, L2 and L3 one would expect three phase, and I have seen some odd readings in the past where a phase is lost specially with no load.

    Today when loop impedance/prospective fault current meters are often to hand I would measure the loop impedance, if both L1 and L2 show same loop impedance then likely split phase, if not then likely three phase and you have lost one.
     
  6. peter palmer

    peter palmer Well-Known Member

    Don't put the loop tester across 2 phases though.
     
  7. Bob Rathbone

    Bob Rathbone Well-Known Member

    Why? There’s no potential between L1+L2 meaning there connected at the one end and line voltage was 240v and phase was between 460V and 483V[/QUOTE]
    That is what you have found but all of the other voltages do not make sense when the calculations are applied, either for a Bi phase or 3 phase supply. If your readings are correct their is a fault.
     

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