US custom (still) is green for earth, white for neutral, and other colors (most commonly black and red) for phases or other non-neutral conductors. A wide variety of other conflicting conventions are or were used throughout the world interfering with a simple scheme. I am aware of black neutrals, red grounds, green phases, and I am sure there were a lot of other conflicts.
Earth was the first general convention with its green/yellow ID that everyone bought into. The US was willing to accept (light) blue as equivalent to white and other countries seemed to be happy with that as well, so Neutral as blue now seems to be internationally accepted. Brown seems to satisfy everyone for phase on single phase supplies. I don't know who the principles were in settling all this but its nice to have some uniformity now. Kudos. Its tough getting changes through national code traditionalists. As far as I know, we have run out of simple colors to name two more universal phase colors, but it may not be important. If rotation does not matter, they can just as well be all the same color. If rotation does matter, then color will not be very informative without a key. You might as well go to labels 1,2,3 or A,B,C so rotation direction is clear. Note also that you cannot rely on phase rotation for safety. Supplies have been known to change accidentally following storm damage or rewiring. As you can see, your color choices would be consistently misinterpreted in the US. Hope this helps toward internationalization. Bob Tatterton Phil MMUk wrote: > > We make an instrument that is powered from a three phase supply. > The instrument power is supplied down a flexible conduit with individual > wires which the customer wires into (his) wall mounted isolator. > The colours used are red-blue-yellow for the phases, black for neutral > and green/yellow for earth. > I have been told that it is a European-wide requirement that the colours > should be brown for all phases, blue for neutral and green/yellow for > earth. > > Can anyone confirm this and perhaps point me to the appropriate > regulations. > > Thanks for any help. > Phil Tatterton > Micromass UK
