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Neutral Voltage Question

Hi all, 


Hoping someone can help with this, as it bothering me that I dont know this. 


This is quite tricky to explain without an image. Essentially, if we have a circuit supplying one luminaire. The line conductor has a voltage of 230v from earth potential supplying the light. To complete the circuit, on the return leg a neutral is required (<50v from earth potential). Where is the point where the neutral is no longer at mains voltage, is it at the neural terminals? 


Is it a case of the luminaire will "use up" the supplied mains voltage? 


Any assistance is appreciated. 


Thanks
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  • Mapj1 - Forum closing soon, so if we get pushed off, please start again in the new place, same title. 


    OK, so the voltage between L and N is 240V or whatever at the substation, and so long as current is flowing, then as we walk along the wires towards the load, voltage is dropped, I * R but R in the wires is very small - we make the wires big enough this is alwys true. As voltage is dropped in the live, the voltage is falling as we move from the source and is nearest earth towards the load end, even if that is only a volt or two lost out of 230. 

    The current in the neutral is flowing the other way, so the voltage drop is upwards - rising a volt or two nearer towards the live at the load end. The load sees a difference relative to the origin, due to both Live and Neutral voltage drops. 


    (the exact voltage may be complicated as the 0v refernce, the N-E bond, may not be at the substation, but the slope is always that way, but some voltages may be below zero as it were - i.e. the phase of the sine wave is inverted.) 

    Hopefully most of the voltage is dropped in the load; and if you could cut the load in half and stick a meter half way along - and with an old fashioned bar type electric heater maybe you could, that point would be equally far from the original L and N, and so at 120 V to earth or so.
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  • Mapj1 - Forum closing soon, so if we get pushed off, please start again in the new place, same title. 


    OK, so the voltage between L and N is 240V or whatever at the substation, and so long as current is flowing, then as we walk along the wires towards the load, voltage is dropped, I * R but R in the wires is very small - we make the wires big enough this is alwys true. As voltage is dropped in the live, the voltage is falling as we move from the source and is nearest earth towards the load end, even if that is only a volt or two lost out of 230. 

    The current in the neutral is flowing the other way, so the voltage drop is upwards - rising a volt or two nearer towards the live at the load end. The load sees a difference relative to the origin, due to both Live and Neutral voltage drops. 


    (the exact voltage may be complicated as the 0v refernce, the N-E bond, may not be at the substation, but the slope is always that way, but some voltages may be below zero as it were - i.e. the phase of the sine wave is inverted.) 

    Hopefully most of the voltage is dropped in the load; and if you could cut the load in half and stick a meter half way along - and with an old fashioned bar type electric heater maybe you could, that point would be equally far from the original L and N, and so at 120 V to earth or so.
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