Power connectors

From: Daniel T. Burrows <danburrows_at_mindspring.com>
Date: Tue Apr 20 10:42:45 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')



That explains the confusion. In the US:
Hot is one phase and in single phase systems you can and do have 2 hots.
Neutral is what you are refering to as ground. The starpoint for both
single and 3 phase.
Ground is the protective / frame ground.

The protective ground (ground in US codes) is not allowed to normally carry
any current. It should be able to be temporarly disconnected and not create
a hazardous condition.

>Second, do I understand that US appliances got fuses on both wires
>and both are switched ?
On 240 volt equipment yes.

The 120 volt plugs are defined with distinct Hot, Neutral and ground pins.
I am familiar with your plugs also and have wondered how hot / neutral
definitions are handled. Think of US 120V plugs like UK plugs just smaller
and without fuses in them.

>Over here in Germany only one wire is
>switched and protected with a fuse, althrough it is not defined
>which one is the 'hot' line, since our connector is symetrical
>- there is no way to insert the plug in a way where the Hot and
>the Ground side is defined - Our plug isn't inherited from the
>DC times, but rather a new design when 220V AC became standard
>in the 30s, to fit the needs of (and only of) AC Eq.

The US did not used to make a distinction between hot and neutral until
about 30 years ago when they added the "protective" ground pin. Now they
are keyed. If you look closely at a receptacle, one blade is wider -
neutral, The narrower blade is Hot and the round pin is protective ground.
Some "equipment" uses only 2 wires. The blades and often one is larger to
assure that it is polarized correctly. These polarized plugs have come into
common usage in the last 20 years.

Dan
Received on Tue Apr 20 1999 - 10:42:45 BST