At the time of said "invention" I don't think the electrical service system was wired the same... at all. There was no fault return whatsoever, and I don't think they used earth grounding in their distributions either.
Yeah... right... Right up to the point when Bill and Intel began ignoring it.
The shameful effect that has had are things like the HD DVD Bluray war.
They should both be around.
On 16 Jun 2008 19:10:10 GMT Andrew Gabriel wrote: | In article , | snipped-for-privacy@ipal.net writes: |> On 16 Jun 2008 08:19:12 GMT Andrew Gabriel wrote: |>| In article , |>| snipped-for-privacy@ipal.net writes: |>|> The design I was thinking of would, first of all, including a round |>|> "ground shell". That would be a metal shield (for arc safety) around |>| |>| We've known how to design connectors which don't generate arcing |>| problems for 70+ years. It really isn't necessary to design arcing |>| in -- you design it out. |> |> Could you give more detail? I've not heard of this. Is it some magic |> metal compound that prevents arcs? Why are utilities not using this |> on their switch stations? | | Look at almost any other country's mains connectors, except | the US ones. This really is pretty much a US-only problem. | At the most basic level, you need contacts with enough pressure | to maintain low contact resistance and no excessive heating. | I'm not sure why US manufacturers haven't resolved this. | It may be that US mains plugs are too small to get sufficient | hand grip to perform insertion/removal with contacts which provide | enough pressure to prevent overheating. They barely have enough | contact pressure to stop the plug falling out under the weight of | its mains lead (certainly after the spring contacts have got hot | and don't have as much spring in them).
My reference to arc safety is not about arcing while the plug is in. That really isn't a problem with properly manufactured outlets and plugs here (but certainly the standards could be improved upon as there are a lot of cheap ones).
Instead, my reference is to the arc that can happen when the plug is inserted and makes contact, or is removed and the contact breaks. I know from experience what kind of arc can happen when a plug is inserted that has a solid short on it (I didn't know it had a short before plugging it in). I've also seen such an event someone else plugged in which was even more spectacular with an arc flash uniformly expanding from the plug about a half meter radius (both outlet and plug were destroyed but the person plugging it in was fortunately uninjured). Breakers kicked off the circuit in both cases.
|>|> the blades, and also serve as the protective ground. Think of the DIN |>|> connector used on older PC keyboards, but a bit larger, with 2 blades |>|> much like the UK plug. But the shell serves as the ground. |>| |>| An exposed ground can cause more problems. |> |> Given that the frame of metallic appliances would be connected to this ground, |> how would this be a problem and it NOT be a problem for the appliance to be |> exposing it? | | Double insulated appliance. | | If you do have a fault somewhere else, it may well be that gripping | a well-earthed plug kills you by completing the current path. | There's a good reason mains plugs do not have exposed conductive | parts (and it's probably a regulatory requirement in some places).
The design can be modified to ground in other ways and still have some kind of shield around, either all non-metal, or a non-metal outer layer.
On 16 Jun 2008 19:49:08 GMT Andrew Gabriel wrote: | In article , | James Sweet writes: |> |> |>> Look at almost any other country's mains connectors, except |>> the US ones. This really is pretty much a US-only problem. |>> At the most basic level, you need contacts with enough pressure |>> to maintain low contact resistance and no excessive heating. |>> I'm not sure why US manufacturers haven't resolved this. |>> It may be that US mains plugs are too small to get sufficient |>> hand grip to perform insertion/removal with contacts which provide |>> enough pressure to prevent overheating. They barely have enough |>> contact pressure to stop the plug falling out under the weight of |>> its mains lead (certainly after the spring contacts have got hot |>> and don't have as much spring in them). |> |> The problem is less the design than the build quality. While I agree |> that many European plug standards are in some ways superior, a good |> quality US receptacle and plug will maintain contact without arcing or |> heating. The problem is that rather than buy $1.80 outlets and $4 plugs |> that are nicely made out of good quality materials, people buy 75 cent |> outlets and $1 plugs that are poorly made and flimsy. When I bought my |> house, it had many receptacles that would not reliably hold a plug, |> particularly big transformer plugs, but I replaced them all with |> commercial grade receptacles that have a nice precise fit with good grip |> on the plug. |> |> It's a little late in the game to come up with a whole new design, just |> tightening the regulations on the quality of the parts would be |> beneficial and a whole lot easier. | | Out of interest, anyone know where/when the original US 2-prong | designed appeared? I'm guessing it's probably one of the oldest | mains plug designs still in use, and some of this is probably | down to the penalty for being one of the first.
I recall reading that it was invented by the Harvey Hubbell Electrical equipment company. That company still exists at least in name, shortened to just Hubbell.
The UL requirement for double insulation does require two barriers to live conductors. Of course different pieces of equipment accomplish this in different ways, some of which might not be immediately obvious on casual inspection.
How does a metal cased US toaster manage this with exposed live elements? A European toaster is exactly the same, but could not claim to be double insulated.
Also, I think most (if not all) US mains flexs I've seen only have a single insulation barrier. That's not allowed in Europe, because it's missing the two barriers.
On 23 Jun 2008 21:24:01 GMT Andrew Gabriel wrote: | In article , | "Ben Miller" writes: |> Andrew Gabriel wrote: |>> In article , |>> Palindrome writes: |>>>
|>>
|>> The concept of double insulated seems to exist in the US too, but |>> the requirements for it don't seem to be the same, specifically |>> don't seem to include the requirement for a double insulation barrier |>> between live parts and a person, based on appliances I see marked as |>> double insulated in the US which don't come close to being double |>> insulated for Europe. |> |> The UL requirement for double insulation does require two barriers to live |> conductors. Of course different pieces of equipment accomplish this in |> different ways, some of which might not be immediately obvious on casual |> inspection. | | How does a metal cased US toaster manage this with exposed | live elements? A European toaster is exactly the same, but | could not claim to be double insulated. | | Also, I think most (if not all) US mains flexs I've seen only | have a single insulation barrier. That's not allowed in Europe, | because it's missing the two barriers.
There insulation around the individual conductors, and insulation around the set of conductors. How many more layers are needed?
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