20 Apr
1999
20 Apr
'99
10:42 a.m.
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
20 Apr
20 Apr
1:31 p.m.
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.
Sorry, just my translation problem, I had to assign names where no
dictionary could help me, And Neutral = Protective Ground vs Ground
seemed to be logical - sorry.
The protective ground (ground in US codes) is not
allowed to normally carry
any current.
Same over here.
Second, do I
understand that US appliances got fuses on both wires
and both are switched ?
On 240 volt equipment yes. >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.
Strange, but common - I don't know any reason why the system has
to be keyed, I always assumed the US development of keyed plugs
was triggered by old DC systems (since in DC Eq. it is necersarry
to know the orientation), but not a new addition. Strange, we
dropped all orientationwhen switching to AC (with Protective
Ground). Could anyone give give a reason why the system has
to be keyed _IF_ a Protective Ground is included (other than
define the Protective Ground pin) ? Because, without Protective
Ground a definition of Neutral is essential, but with, no longer.
I'm realy courious, since this is the kind of technology I'm
originated - I studied Starkstromelektronik (Power Electronics)
after (high)school.
Thanks
Hans
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Ich denke, also bin ich, also gut
HRK
8:50 p.m.
On 20 Apr 99 at 18:32, Hans Franke wrote:
First of all it should be called NA standards as Canada is also part of the NA
grid and has TMK slightly more stringent standards. The Generating station
transmits through the Bulk Transmission System at 500kv to a regional
Transformer station which retransmits at 230kv via the Regional Supply System
to a local Transformer station which then supplies Municipal and local
distribution systems at 600v. Typical residential and small commercial supply
is then provided with 240v single phase. Larger commercial or industrial supply
is 3phase 208v or 600v measured phase to phase. As an aside, the large mobile
generators seen on movie sets generate 3 phase 208v because of lighting power
demands.
The correct terminology here is Line, Neutral, and Isolated Ground. equivalent
to the red or black, white, and green wires. Because of fluctuations in supply
the neutral to line configuration is referred to as 110/120 while the line to
line one is 220/240. Most higher-power or supply critical 110/120 devices use
the 3prong plug. Cooking ranges, dryers , and some air-conditioners use the
220/240 configuration and now must in most jurisdictions use 4prong plugs.
Usually red, black. white, and green wiring.
Where problems arise is that most older wiring does not comply to the
new(relatively) specs regarding grounding, much less the keyed plugs. There
are many houses still with 2 wire systems and an adapter called a "cheater" is
available in most hardware stores to circumvent the 3 prong grounded plug. It
has a ground wire to attach to the faceplate screw, which most people ignore.
Even that supposes that the switch receptical is properly grounded via the coax
cable used in many older installations. I have also seen 3-wire 220 without any
ground in many older houses.
Not always.
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.
Sorry, just my translation problem, I had to assign names where no
dictionary could help me, And Neutral = Protective Ground vs Ground
seemed to be logical - sorry.
The protective ground (ground in US codes) is
not allowed to normally carry
any current.
Same over here.
Second, do I understand that US appliances got fuses on
both wires
and both are switched ?
On 240 volt equipment yes. Ahh ja - we also use fuses in each 'Hot' wire
- so if you have a
3~ installation, 3 fuses are to be installed _and_ they have to
be tied (mechanical), so if one blows all 3 will go off.
I think the keyed plugs have more to do
with modern equipment needs such as
X-10 (? the control system) ,than safety or power quality concerns.
>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.
Strange, but common - I don't know any reason why
the system has
to be keyed, I always assumed the US development of keyed plugs
was triggered by old DC systems (since in DC Eq. it is necersarry
to know the orientation), but not a new addition. Strange, we
NA switched from Edisons DC systems as in NYC to Tesla/Westinghouse AC
early on due to the better power transmission over the greater distances
occasioned in NA.
dropped all orientationwhen switching to AC (with
Protective
Ground). Could anyone give give a reason why the system has
to be keyed _IF_ a Protective Ground is included (other than
define the Protective Ground pin) ? Because, without Protective
Ground a definition of Neutral is essential, but with, no longer.
I'm realy courious, since this is the kind of technology I'm
originated - I studied Starkstromelektronik (Power Electronics)
after (high)school.
Thanks
Hans
There also has to be a differentation made between safety ground
and signal ground. AC power ground is generally only at low impedance
at low frequencies. Also if signal and power ground is connected at
more than one point, a ground loop can be created as I'm sure you're
aware.
One of the differences between the Canadian Electrical Safety Code
and it's US counterpart the National Electrical Code is that Isolated
Ground circuits must bypass the panel board and be connected to
"Earth Ground" at supply entry. This avoids any interaction with the
supply panel.
ciao larry
lwalker(a)interlog.com
Collectors List and info http://members.xoom.com/T3C
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2 comments
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participants (3)
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danburrows＠mindspring.com -
Hans.Franke＠mch20.sbs.de -
lwalker＠mail.interlog.com