Post by thread:[OT] Burning the hot side of the plug

I have not yet seen an explanation that is believeable. Possibly the fact that the hot side is at higher potential with respect to air/environment (which I assume is near ground) causes a long term chemical reaction that raises the resistance of the hot side. Gus -- Gus Calabrese Lola Montes WFT Electronics 4337 Raleigh Street Denver, CO 80212 303 964-9670......voicemail spam_OUTwftTakeThisOuTfrii.com http://www.frii.com/~wft EMERGENCY: 791 High Street Estes Park, CO 80517 if no success with .....wftKILLspam@spam@frii.com, try .... wftKILLspambigfoot.com then .....wftKILLspam.....eudoramail.com

Gus Calabrese <EraseMEwftspam_OUTTakeThisOuTMAIL.FRII.COM> wrote: > I have not yet seen an explanation that is believeable. Oh dear! Was my explanation not believeable? Shall I try and re-state it stepwise? 1) The problem occurs mostly on outlets used for medium to high current loads. 2) By implication, it is caused by current in the circuit, not voltage across the adjacent pins. 3) Current causes *heating* in the contacts. The contacts are constructed from phosphor-bronze or similar material, tempered by the stamping process used to fabricate them. 4) Heating above a certain temperature causes annealing so that the contacts soften and the contact force decreases, raising the contact resistance. Heating of the chlorocarbon plastics used in plugs causes release of monomer and to some extent, free chloride which corrodes even corrosion-resistant alloys. 5) Loss of contact by these mechanisms causes further IÓR heating so this is a non-linear (compounding) effect. 6) The live and neutral contacts in the socket are *different* as the live goes to the switch contact whilst the neutral goes to a screw terminal where it is anchored to the incoming cable and in the case of double outlets, to the opposite outlet assembly. Consequently, the live contact is less firmly anchored and more likely to have poor contact in the first place. 7) A most significant corollary: The live contact is not heat-sunk by attachment to a larger area of metal including the incoming cable. Further, it is subject to aditional contact heating from any poor contact in the switch mechanism. In summary, it is little surprise that the live contact overheats by preference, *on a switched outlet*. I doubt you will observe the phenomenon on an unswitched outlet except *of course* where this is used with a previously damaged plug. Cheers, Paul B.

On Mon, 27 Jul 1998, Paul B. Webster VK2BZC wrote: - snip - > In summary, it is little surprise that the live contact overheats by > preference, *on a switched outlet*. I doubt you will observe the > phenomenon on an unswitched outlet except *of course* where this is used > with a previously damaged plug. So sorry to burst your bubble, but I was talking about our plugs (which I have drawn before) and Euro amd Schukos. These are all symmetrical, there is no physical difference between the attachments. The effect exists, but I have no statistical data to confirm it... and I never implied anything but brand new plugs used normally for a few years. Peter

Peter, Paul For some sockets the contacting "fingers" are designed for access by plug pins of less thickness than that of a common electrical test meter's probe's diameter. An electrician will statistically test Phase (live 110/220 AC etc) more often than the Nutral connection. (Earth also tested) This is a potential cause for stressing of Phase connection more than Nutral. In addition, Peter's should perhaps reread Paul's one significant point(No.7) which explained that the switched PHASE connection *ON THE SOCKET* has a greater cooling volume due to the thick copper track leading to the switch. Regards, Graham Daniel (Electrician day job but counting down) Peter L. Peres wrote: {Quote hidden}> > On Mon, 27 Jul 1998, Paul B. Webster VK2BZC wrote: > > - snip - > > In summary, it is little surprise that the live contact overheats by > > preference, *on a switched outlet*. I doubt you will observe the > > phenomenon on an unswitched outlet except *of course* where this is used > > with a previously damaged plug. > > So sorry to burst your bubble, but I was talking about our plugs (which I > have drawn before) and Euro amd Schukos. These are all symmetrical, there > is no physical difference between the attachments. The effect exists, but > I have no statistical data to confirm it... and I never implied anything > but brand new plugs used normally for a few years. > > Peter

G.Daniel Invent Design wrote: > Peter, Paul > > For some sockets the contacting "fingers" are designed for access by > plug pins of less thickness than that of a common electrical test > meter's probe's diameter. An electrician will statistically test Phase > (live 110/220 AC etc) more often than the Nutral connection. (Earth also > tested) > > This is a potential cause for stressing of Phase connection more than > Nutral. > > In addition, Peter's should perhaps reread Paul's one significant > point(No.7) which explained that the switched PHASE connection *ON THE > SOCKET* has a greater cooling volume due to the thick copper track > leading to the switch. I had a look, and the length of wire connecting the sockets are such that any cooling effect of a switch can be ruled out. The wire guages are identical. The pins on the plug are also identical. -- Friendly Regards Tjaart van der Walt tjaartspam_OUTwasp.co.za |--------------------------------------------------| | WASP International | |R&D Engineer : GSM peripheral services development| |--------------------------------------------------| |SMS @spam@tjaartKILLspamsms.wasp.co.za (160 chars max)| | http://www.wasp.co.za/~tjaart/index.html | |Voice: +27-(0)11-622-8686 Fax: +27-(0)11-622-8973| | WGS-84 : 26¡10.52'S 28¡06.19'E | |--------------------------------------------------|

Grrr! Tjaart van der Walt and G.Daniel Invent Design wrote referring to a "cooling" effect of the switch on the live pole. That's *not* what I said! I suggested that the connection to the switch, being a *smaller* piece of metal, *not* connected to the incoming cables from the wall, and the possibility of poor contact in the switch mechanism being an additional source of heat, means that this (live) contact is *poorly* heat-sunk and therefore runs *hotter*; not surprisingly; overheating. Is that clear? -- Cheers, Paul B.

This whole thing about which lead wears quicker might bear some relationship to brushed motors, where one pole consistenly wears more than the other (the + side). Perhaps somebody might like to investigate that avenue. Andy ================================================================== Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA ==================================================================

> I suggested that the connection to the switch, being a *smaller* piece >of metal, *not* connected to the incoming cables from the wall, and the >possibility of poor contact in the switch mechanism being an additional >source of heat, means that this (live) contact is *poorly* heat-sunk and >therefore runs *hotter*; not surprisingly; overheating. > > Is that clear? Yep. I just wonder: Is this a manually operated switch, or operated by the plug? For safety? /Morgan > Cheers, > Paul B. > > / Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \ \ KILLspammrtKILLspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331 /

Andy Kunz wrote: > This whole thing about which lead wears quicker might bear some > relationship to brushed motors, where one pole consistenly wears more than > the other (the + side). > > Perhaps somebody might like to investigate that avenue. It is AC. -- Friendly Regards Tjaart van der Walt RemoveMEtjaartTakeThisOuTwasp.co.za |--------------------------------------------------| | WASP International | |R&D Engineer : GSM peripheral services development| |--------------------------------------------------| |SMS spamBeGonetjaartspamBeGonesms.wasp.co.za (160 chars max)| | http://www.wasp.co.za/~tjaart/index.html | |Voice: +27-(0)11-622-8686 Fax: +27-(0)11-622-8973| | WGS-84 : 26¡10.52'S 28¡06.19'E | |--------------------------------------------------|

On Tue, 28 Jul 1998, Andy Kunz wrote: > This whole thing about which lead wears quicker might bear some > relationship to brushed motors, where one pole consistenly wears more than > the other (the + side). That one is easy. The constant arcing transports electrons in one direction and ions in the other through plasma hot enough to melt the electrodes locally. At equal electrode temperature, the material with lower valence per volume unit should electromigrate more, per volume unit (Cu = 1 and dense, C = 4, but far less dense). This neglects mechanical side effects and the *side* of a given arc that gets hotter, plus thermal conductivity. Now, if you add all this up, you have a soft bronze carbon electrode that is the '+' pole in an electric arc, facing a bronze armature that is moving very fast, so any debris extracted from the carbon do not adhere to the moving armature, which conducts heat better, and stays colder on account of its larger mass... hope this helps ;) Peter PS: Was this short enough ?