Power connectors

From: Steve Robertson <steverob_at_hotoffice.com>
Date: Tue Apr 20 10:26:20 1999

> First, to get common names:
> Hot = one Phase
> Neutral = Protective Ground
> Ground = Ground (the starpoint on 3 phases connected to earth at the
'generator')
> Hot and Ground are the basic wires to tap power,

Wrong... HOT and NEUTRAL provide the power legs. Earth Ground is only for
protection and does not carry any power.

The power company generates three phase because it is more efficient.
However, in most residential areas they only provide a single phase. It
doesn't make economic sense for them to string three wires when a single
phase will suffice.

The single phase (high voltage) is fed into a simple center tapped
transformer where it provides 240 VAC for high power appliances and
2-phases each with 120 VAC for lighting and general use.



            || <---------- 120 VAC (HOT)
----------> || <
> || <
   HV > || <---------- Neutral
> || <
----------> || <
            || <---------- 120 VAC (HOT)



In the early days, it was common for manufactures to use the device chassis
or frame as a conductor. They would tie the Neutral wire to the chassis
(under the assumption that the potential was near 0V) and save a few
pennies in the manufacturing process. The problem was, it was possible to
put the plug in the socket upside-down. This meant the chassis was tied to
the hot leg and you could get electrocution just touching the device. In
the 50's and 60's it was quite possible to get shocked by your TV by just
turning it on!

Today, most devices have polarized plugs so that can't happen.

The neutral line should NEVER be fused. If that fuse happened to blow and
the one on the HOT(s) leg didn't, the device would still be hot (even with
a blown fuse). This would cause an unsafe condition.


Steve Robertson - <steverob_at_hotoffice.com>
Received on Tue Apr 20 1999 - 10:26:20 BST

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