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Three phase metering and neutrals

tattyinengland
I have been asked by the owner of a saw mill: Does a three phase meter (Old rotating wheel type) need to have a neutral connected to it in order to work correctly?


This is a property that only uses three phase motors for a saw mill and some lights (That I assume are single phase but quite how that works I'm not sure..........)


This is in a far flung country and is probably a TT system with no earths at all and certainly no RCDs. 


AJ - I managed to delete my last post when I was trying to attach a picture; I know you replied to me previous post, thank you very much, and I'm sorry to have deleted your reply to me. 


It seems that there are no neutrals what so ever into this saw mill......It looks to me like the terminals for the neutral are present but no neutral is connected. 


It may be that the lights are connected to earth as I know that there has been a lot of equi-potential type bonding going on - on this property between machines, structural steelwork, in the ground, all sorts. 


I cant get out there to see whats going on or advise at all because I cant see what effect my advise would have. Certainly if there is single phase lighting going on the neutral is essential. 


The metering I could possibly, with your help advise on. I'd love to post a picture but I'm not sure how. I'll copy this message now and try again........Dammed if I know how to attach a photo........
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    A three phase meter of the type illustrated is intended to have a neutral connected at the meter even if the load requires no neutral.

    Without any neutral connection, the meter will still work for the reasons already given, in that the three equal voltage coils, one for each phase will in effect create an artificial neutral. I suspect that the accuracy would be reduced.


    What is the supply voltage ? if it is 220/380 as marked on the meter, then no standard or common type of light fitting can be used between phases. Options include series pairs of filament lamps each of 220 volt to 240 volt rating, or if the nominal 380 volts between phases is on the low side, then series  triplets of 115 volt or 120 volt lamps can work well. Some switch start fluorescent lamp circuits can be worked two in series on 380 volt circuits. Or imported multi voltage ballasts intended for use on supplies of up to 480 volts.


    Or off course the actual supply might be 3 phase, 3 wire with 220/240 volts between phases, in which case standard 220/240 volt lights may be used between any two phases.
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    A three phase meter of the type illustrated is intended to have a neutral connected at the meter even if the load requires no neutral.

    Without any neutral connection, the meter will still work for the reasons already given, in that the three equal voltage coils, one for each phase will in effect create an artificial neutral. I suspect that the accuracy would be reduced.


    What is the supply voltage ? if it is 220/380 as marked on the meter, then no standard or common type of light fitting can be used between phases. Options include series pairs of filament lamps each of 220 volt to 240 volt rating, or if the nominal 380 volts between phases is on the low side, then series  triplets of 115 volt or 120 volt lamps can work well. Some switch start fluorescent lamp circuits can be worked two in series on 380 volt circuits. Or imported multi voltage ballasts intended for use on supplies of up to 480 volts.


    Or off course the actual supply might be 3 phase, 3 wire with 220/240 volts between phases, in which case standard 220/240 volt lights may be used between any two phases.
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