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??!!

 

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?

 

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?

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

 

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.

 

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