indication lights for 3 phase power

Discussion in 'The Projects Forum' started by Willem M, Mar 17, 2013.

  1. Willem M

    Thread Starter New Member

    Mar 16, 2013
    1
    0
    Hi

    I want to build a circuit that will indicate if there is phase failure. The tricky part is that it must indicate witch
    one of the 3 phases are down. ( an indicator light for each phase).
    Line to line = 380V
    50Hz
    Sorry about the spelling and grammar (afrikaans )

    Can any one help please??!!
     
    Last edited: Mar 17, 2013
  2. richard.cs

    Member

    Mar 3, 2012
    162
    31
    Three neon lamps wired L1-N, L2-N, L3-N? All 3 lit when everything is ok, if a phase goes down that lamp goes out. Or is this a delta system with no neutral?
     
  3. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    Don't expect this to work if there is a 3 phase motor load running when the failure happens. The running motor will "generate" the missing phase to a level high enough to keep the light on. Several manufacturers (Spuare-D, Allen Bradley are two) make phase loss relays for the exact purpose.
    A better way may be to use a 3 phase current monitor such as this.....

    http://www.ayainstruments.com/loss-detector.html
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,664
    634
    If you use neon lamps, be sure to use a resistor. In the case of an NE-2 neon bulb, two 100k 1/2 watt resistors in series with each NE-2 should supply enough current to light the bulb and also stand off the high voltage.
     
  5. richard.cs

    Member

    Mar 3, 2012
    162
    31
    Bill makes a good point about running motors generating the third phase, something I hadn't considered. What is your actual application?
     
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