From: schmidt@auvax1.adelphi.edu
Subject: Re: Various national colour code of wires(e.g. earth) for elec. plug
Organization: Adelphi University, Garden City NY
Date: Mon, 9 Nov 1992 05:23:25 GMT

In article <wai.721266966@phoenix>, wai@socs.uts.edu.au (Wai Yat Wong) writes:
> Anybody out there can tell me about the colour coding various
> country use for labelling a wire as active or neutral or
> ground.
>  
> I know that green is obviously earth, but I have this
> two extra wire; one of them is white, the other is
> black. Does the white go to the active pin and
> black go to the neutral pin?

It's the other way around, white is the "neutral" or in your terminoligy,
"earthed" current-carrying color (the green, as you stated, is the protective
ground, connected to the metallic case).  The black, or any other color than
white or green, the US code only defines the green and white, is the "hot" 120
volt lead.

In the case of 240 volt devices, there should be no white wire, two colors
(usually black and red), and the green safety ground.  Three phase devices
(nominally 208 volts "Y", or 240 volts "delta" would have three colors (most
commonly black, red, and blue) possibly a white neutral, if wye connected, and
a green ground.

Since portable cordage is hard to get without a white wire, you will often find 
240 volt equipment with a white wire in the cord. There is an exception in the
Electric Code to permit this.  In the USA, 240 volt devices normally have both
conductors hot, 120 volts to ground, of opposite polarity (i.e. 180 degrees out 
of phase with each other) and no current carrying ground connection.  

Most of this equipment (certainly anything made for the international market,
which can be easily connected either 120 volts or 240) can be safely connected
to a "rest of the world" grounded 240 volt system.  This does, however, double
the voltage between the "hot" conductor, and anything in the device connected
to it; and the green "ground" lead (and presumably the "chassis" or case.  If
the equipment is not rated bu one of the testing agencies in the 240 volt
world, you might want to look closely at the schematic to make sure that surge
protectors, bypass capacitors, and the like are of adequate rating.

Theoretically, the "white" wire should be the low side in such a 240 volt
application, but it probablu makes little difference in most properly designed
equipment, with the possible exception of some switching power supplies.
>  
> Also, the only thing I know about alternate current is
> that the current flows both way alternatively. Then please
> explain to me why there is a voltage (240 V) between active
> and ground, but nothing between neutral and ground?

In the USA, we use a "center tapped" system for single phase power, where the
center tap of the 240 volts is connected to the ground, and each of the two
"hot" conductors, of the three current carrying conductors (white, black, and
red, nominally) is 'swinging in opposite directions, so most equipment, which
uses 120 volts, is connected between the neutral and one or the other of the
"hot" wires, while 240 volt devices, usually large loads such as electric
stoves, ("cookers", you call them??) water heaters  (I heard these referred to
as "geysers" while visiting southern Africa, I guess that's what happens when
the thermostat sticks on!), and air conditioners, are connected between the two
"hots", with no connection to the neutral. (Actually, stoves often use the
neutral as a way of getting a reduced voltage for lower heat settings on the
"burners".) 

The green "ground" is an independent path back to ground, to
provide safety in case the neutral becomes broken, which will cause it to have
120 volts on it, through the load, and to prevent leakage or neutral volyage
drop from making the case "slightly" hot, which could be dangerous in wet
locations or cause high current, low voltage arcs between equipment with
different neutral connections, if the neutral was used as a case ground.

In the rest of the world, one side of the 240 volts is connected to ground,
which means that conductor, the low side, has no, or a very low, voltage to
ground; and the other conductor has the full 240 volts.  On an instantaneous
basis it swings between (+240 X 1.41) and (-240 X 1.41) 50 times per second. 
240 volts is the "RMS" or root-mean-square voltage, which is the AC voltage
which has the same "heating" value in a resistive load as 240 volts DC would. 
This can be proven mathematically.  (note, the 1.41 multiplier only applies to
sine waves, such as are usually used for power distribution.)  Once again the
green wire is a seperate ground wire provided for safety.  At some point in the
system, usually at the service entrance in the USA, it is connected to the
Neutral, or low wire.  

In other parts of the world, I believe the "low" wire is generally blue, the
"hot" is brown.  In fact the USA national electric code now allows portable
equipment with cords with a blue neutral instead of white, to allow overseas
cord sets to be used in the USA.

>  
> Finally , for U.S.A's electrical plug, which pin is always
> designated as active (the smaller one)? 
 
For the standard, flat bladed 120 volt plug, yes, the narrow blade is the hot,
the wide blade is the neutral, and the "U" shaped pin is the safety ground.

Somewhere, I have a catalog from a company which makes international cord sets
which has wiring diagrams for almost every standard in the world.  When I
visited southern Africa, I bought a copy of the Sowetan, a paper aimed at the
residents of Soweto, South Africa.  I was surprised to find inside a full page
advertisement from the electric utility showing how to connect the cord to
their plug (the same one used in India and numerous former British colonies,
but not in Britian itself) The plug was "large" like the British one, but had
round pins where the British one had rectangular ones.  The same one was used
in Botswana, where I spent most of my time, and, as I remember, in Zimbabwe. 
My "universal adapter" set wasn't, and I had to go to an electric shop which
had an adapter to the "British" style, which I then plugged my adapter into,
which I then plugged my transformer into, etc..   So much for world standards.

John 

> Also, I like to
> find out the info for Australian systems.
> 
> Please educate me, the ignorant sponge :-)
> 
> My email address is wai@socs.uts.edu.au
> 
> (I hope I did not double posted this, as I got a message claiming
>  that my previous post failed )
> 
You did, but that's ok, your "sig" got chopped off the first post. 
> --
> #########################################################################
> ( Wai Yat Wong          | School of Computing Sciences                  )
> ( Phone No. : 330-1841  | University of Technology, Sydney, NSW 2007    )
> ( Fax No.   : 330-1807  | wai@socs.uts.edu.au                           )
-- 
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John H. Schmidt, P.E.              |Internet: schmidt@auvax1.adelphi.edu
Technical Director, WBAU           |Phone--Days     (212)456-4218
Adelphi University                 |       Evenings (516)877-6400
Garden City, New York 11530        |Fax-------------(212)456-2424
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