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Two way+intermediate domestic light circuit extraneous voltage head scratching

Colin Stares

Hi my house is supplied via T-T system, the pole mounted mains transformer is 100mts away,

the measured Ze is 120ohms

on a two way+intermediate circuit I’m measuring 60-90vac when the light is in any off position,

I have disconnected all circuit wires and it all measured clear, the circuit is blowing led lamps and fluorescent lamps are pulsing when in off positions, any ideas!!!

Parents

  • Almost certainly capacitive coupling between an always live wire and the switched live to the lamps. The degree of such capacitive coupling will depend upon the circuit layout and cable lengths. Often called induction, but capacitive coupling is a more accurate description.

    I would be surprised if the phenomena was destroying the lamps. More likely cheap lamps that fail early.

    The only simple cure is to shunt the lamps with a small MAINS RATED capacitor such as a small power factor correction capacitor as used in fluorescent lamp circuits.

  • in reply to broadgage

    Hi broardgage, I have fitted a 0.1microfarad ac capacitor as suggested and the voltage is now 3vac, I think that’s a result and all is now working ok.

    colin

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  • in reply to broadgage

    Hi broardgage, I have fitted a 0.1microfarad ac capacitor as suggested and the voltage is now 3vac, I think that’s a result and all is now working ok.

    colin

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