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Stupid question of the day....
|
|
| AllTel - Jim Hubbard 2005-07-30, 12:21 am |
| I am curious about what would happen to an electrical current in 2
situations.....
Assume that you have 2 wires that, when joined, complete a closed electrical
DC circuit with electrons flowing thusly.....
------------ ============
eeeeeeeeee eeeeeeeeeeeeeee
------------ ============
If you flattened out the end of each wire where they connect , would the
resulting electron paths be more like figure A or Figure B?
Figure A
--- ===
--- ===
--- ===
--- ===
eeeeeeeee eeeeeeeeeeeeeeee
--- ===
--- ===
--- ===
--- ===
Figure B
--- e e ===
--- eee eeeeee ===
--- eeeee eeeeeeeeee ===
--- eeeeeee eeeeeeeeeeee ===
eeeeeeeeeee eeeeeeeeeeeeeeeee
--- eeeeeee eeeeeeeeeeeee ===
--- eeeee eeeeeeeee ===
--- eee eeeee ===
--- e e ===
(Please note that the vast # of "e"lectrons shown in Figure B is simply to
show the path's of electrons. )
The second portion of my question is....If the flattened portions were
increases in mass (if each wire were connected to a metal cube and the cubes
were brought together to complete the circuit) how would it effect electron
flow where the cubes touch?
Thanks for your help.
| |
| John Popelish 2005-07-30, 1:21 am |
| AllTel - Jim Hubbard wrote:
> I am curious about what would happen to an electrical current in 2
> situations.....
>
> Assume that you have 2 wires that, when joined, complete a closed electrical
> DC circuit with electrons flowing thusly.....
>
> ------------ ============
> eeeeeeeeee eeeeeeeeeeeeeee
> ------------ ============
>
>
> If you flattened out the end of each wire where they connect , would the
> resulting electron paths be more like figure A or Figure B?
>
> Figure A
>
> --- ===
> --- ===
> --- ===
> --- ===
> eeeeeeeee eeeeeeeeeeeeeeee
> --- ===
> --- ===
> --- ===
> --- ===
>
>
> Figure B
>
> --- e e ===
> --- eee eeeeee ===
> --- eeeee eeeeeeeeee ===
> --- eeeeeee eeeeeeeeeeee ===
> eeeeeeeeeee eeeeeeeeeeeeeeeee
> --- eeeeeee eeeeeeeeeeeee ===
> --- eeeee eeeeeeeee ===
> --- eee eeeee ===
> --- e e ===
>
> (Please note that the vast # of "e"lectrons shown in Figure B is simply to
> show the path's of electrons. )
>
> The second portion of my question is....If the flattened portions were
> increases in mass (if each wire were connected to a metal cube and the cubes
> were brought together to complete the circuit) how would it effect electron
> flow where the cubes touch?
>
> Thanks for your help.
Every atom in the conductor contributes an electron to the moving
herd. If you alter the cross section or shape of the conductor, the
total number of electrons taking part in the flow across any cross
section changes in proportion to the cross sectional area (with cross
section being defined as perpendicular to the local E field that
motivates the flow).
Since the current (number of electrons passing through a cross
section) has to be uniform, all around a current carrying loop, the
average velocity of the electrons must vary inversely to the cross
sectional area. If more of them are carrying a given current, they go
slower. If fewer have to carry that current, they mist move faster.
I think these rules cover all your cases.
| |
| Repeating Rifle 2005-07-30, 3:21 am |
| On 7/29/05 8:15 PM, in article 232f7$42eaf0d2$97d59ba4$23531@ALLTEL.NET,
"AllTel - Jim Hubbard" <reply@newsgroups.com> wrote:
> I am curious about what would happen to an electrical current in 2
> situations.....
<snip>
It is not a stupid question--it is just irrelevant. Current flows in various
ways, and in almost all cases, the details of the flow is unimportant. The
"wires" can be made from metals, semimetals, hot glass, semiconductors,
ionic solutions, etc. Each has a different kind of conduction mechanism.
I have taken the probably impossible task upon myself to discourage thinking
of conduction as a flow of electrons.
Bill
| |
| TimPerry 2005-07-30, 3:21 am |
|
"AllTel - Jim Hubbard" <reply@newsgroups.com> wrote in message
news:232f7$42eaf0d2$97d59ba4$23531@ALLTEL.NET...
> I am curious about what would happen to an electrical current in 2
> situations.....
>
> Assume that you have 2 wires that, when joined, complete a closed
electrical
> DC circuit with electrons flowing thusly.....
>
> ------------ ============
> eeeeeeeeee eeeeeeeeeeeeeee
> ------------ ============
>
>
> If you flattened out the end of each wire where they connect , would the
> resulting electron paths be more like figure A or Figure B?
>
neither ... research "skin effect"
> Figure A
>
> --- ===
> --- ===
> --- ===
> --- ===
> eeeeeeeee eeeeeeeeeeeeeeee
> --- ===
> --- ===
> --- ===
> --- ===
>
>
> Figure B
>
> --- e e ===
> --- eee eeeeee ===
> --- eeeee eeeeeeeeee ===
> --- eeeeeee eeeeeeeeeeee ===
> eeeeeeeeeee eeeeeeeeeeeeeeeee
> --- eeeeeee eeeeeeeeeeeee ===
> --- eeeee eeeeeeeee ===
> --- eee eeeee ===
> --- e e ===
>
> (Please note that the vast # of "e"lectrons shown in Figure B is simply to
> show the path's of electrons. )
>
> The second portion of my question is....If the flattened portions were
> increases in mass (if each wire were connected to a metal cube and the
cubes
> were brought together to complete the circuit) how would it effect
electron
> flow where the cubes touch?
electron flow (or hole flow is you prefer to think that way) is determined
by total circuit resistance. (and applied EMF as per ohms law) decreasing
total resistance by increasing contact point surface area will result in
increased current flow if all other factors remain the same.
>
> Thanks for your help.
>
>
| |
| Andrew Gabriel 2005-07-30, 7:21 am |
| In article <WrqdndPloplTh3bfRVn-3w@adelphia.com>,
"TimPerry" <timperry@noaspamadelphia.net> writes:
> "AllTel - Jim Hubbard" <reply@newsgroups.com> wrote in message
> news:232f7$42eaf0d2$97d59ba4$23531@ALLTEL.NET...
>
> neither ... research "skin effect"
You missed that I guess?
--
Andrew Gabriel
| |
| Alexander 2005-07-30, 9:21 am |
|
"TimPerry" <timperry@noaspamadelphia.net> schreef in bericht
news:WrqdndPloplTh3bfRVn-3w@adelphia.com...
>
> "AllTel - Jim Hubbard" <reply@newsgroups.com> wrote in message
> news:232f7$42eaf0d2$97d59ba4$23531@ALLTEL.NET...
> electrical
>
> neither ... research "skin effect"
Most of the times this just aplies to AC (high frequency) circuits
>
>
> cubes
> electron
>
> electron flow (or hole flow is you prefer to think that way) is determined
> by total circuit resistance. (and applied EMF as per ohms law) decreasing
> total resistance by increasing contact point surface area will result in
> increased current flow if all other factors remain the same.
>
>
>
>
| |
| JoeSixPack 2005-07-30, 12:21 pm |
|
"John Popelish" <jpopelish@rica.net> wrote in message
news:s-KdnfGChL8JanffRVn-pQ@adelphia.com...
> AllTel - Jim Hubbard wrote:
>
> Since the current (number of electrons passing through a cross section)
> has to be uniform, all around a current carrying loop, the average
> velocity of the electrons must vary inversely to the cross sectional area.
> If more of them are carrying a given current, they go slower. If fewer
> have to carry that current, they mist move faster.
Before you attack this post, saying electrons can only travel at the speed
of light, that's incorrect. The electrons themselves can travel any speed,
but the voltage wave produced does travel at 300,000 kms per second.
| |
| John Larkin 2005-07-30, 2:21 pm |
| On Fri, 29 Jul 2005 23:15:20 -0400, "AllTel - Jim Hubbard"
<reply@newsgroups.com> wrote:
>I am curious about what would happen to an electrical current in 2
>situations.....
>
>Assume that you have 2 wires that, when joined, complete a closed electrical
>DC circuit with electrons flowing thusly.....
>
>------------ ============
>eeeeeeeeee eeeeeeeeeeeeeee
>------------ ============
>
>
>If you flattened out the end of each wire where they connect , would the
>resulting electron paths be more like figure A or Figure B?
>
>Figure A
>
> --- ===
> --- ===
> --- ===
>--- ===
>eeeeeeeee eeeeeeeeeeeeeeee
>--- ===
> --- ===
> --- ===
> --- ===
>
>
>Figure B
>
> --- e e ===
> --- eee eeeeee ===
> --- eeeee eeeeeeeeee ===
>--- eeeeeee eeeeeeeeeeee ===
>eeeeeeeeeee eeeeeeeeeeeeeeeee
>--- eeeeeee eeeeeeeeeeeee ===
> --- eeeee eeeeeeeee ===
> --- eee eeeee ===
> --- e e ===
>
>(Please note that the vast # of "e"lectrons shown in Figure B is simply to
>show the path's of electrons. )
>
>The second portion of my question is....If the flattened portions were
>increases in mass (if each wire were connected to a metal cube and the cubes
>were brought together to complete the circuit) how would it effect electron
>flow where the cubes touch?
>
>Thanks for your help.
>
For DC or low-frequency AC, charge flow will be uniform across the
cross-section of a round wire conductor (or, actually, any shaped
conductor with unchanging cross-section.) If you butt two clean-cut
wires against each other, they're now effectively a single wire, so
current distribution is still uniform.
The cube situation is more complex. A wire pokes a nearly uniform
circle of current into the cubes, and the other wire (by symmetry)
sucks it up uniformly across its cross-section, but the current
spreads out as it passes through the large cube, most diffuse halfway
through and necking down near the entry/exit circles at the wires. The
exact current distribution within the cube is complex, usually
computed using finite-element simulation. It might be possible to use
calculus to compute this distribution, but I wouldn't want to try.
At higher frequency AC, current in a wire tends to avoid the center
and crowd near the surface, "skin effect."
John
| |
| John Popelish 2005-07-30, 2:21 pm |
| JoeSixPack wrote:
> "John Popelish" <jpopelish@rica.net> wrote in message
> news:s-KdnfGChL8JanffRVn-pQ@adelphia.com...
>
>
> Before you attack this post, saying electrons can only travel at the speed
> of light, that's incorrect. The electrons themselves can travel any speed,
> but the voltage wave produced does travel at 300,000 kms per second.
Before you attack this post for saying that electrons can travel at
any speed, keep in mind that Joe probably understands that this
includes any speed up to, but not including, the speed of light. ;-)
Thanks for helping out, Joe.
| |
| John Fields 2005-07-30, 3:21 pm |
| On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack" <olegp@telus.net>
wrote:
>Before you attack this post, saying electrons can only travel at the speed
>of light, that's incorrect. The electrons themselves can travel any speed,
---
No, they can only travel at speeds less than the speed of light.
---
>but the voltage wave produced does travel at 300,000 kms per second.
---
It's not a "voltage" wave, it's an electromagnetic wave, and it can
only propagate at the speed of light in a vacuum.
--
John Fields
Professional Circuit Designer
| |
| John Larkin 2005-07-30, 3:21 pm |
| On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>At higher frequency AC, current in a wire tends to avoid the center
>and crowd near the surface, "skin effect."
>
Hmmm...
Copper does have a weak Hall effect. And the current through a round
wire does make a circular/transverse magnetic field. So, at very high
DC currents, is the current density a bit non-uniform?
John
| |
|
| John Fields wrote:
> On Sat, 30 Jul 2005 15:14:37 GMT, "JoeSixPack" <olegp@telus.net>
> wrote:
>
>
>
>
> ---
> No, they can only travel at speeds less than the speed of light.
> ---
>
>
>
>
> ---
> It's not a "voltage" wave, it's an electromagnetic wave, and it can
> only propagate at the speed of light in a vacuum.
>
i am glad some one is on the ball here!  )
--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
| |
| TimPerry 2005-07-30, 4:21 pm |
|
"Andrew Gabriel" <andrew@a17> wrote in message
news:42eb472a$0$38039$5a6aecb4@news.aaisp.net.uk...
> In article <WrqdndPloplTh3bfRVn-3w@adelphia.com>,
> "TimPerry" <timperry@noaspamadelphia.net> writes:
>
> You missed that I guess?
>
> --
> Andrew Gabriel
researching skin effect will give the poster a better understanding of
electron distribution in a conductor than short answers on the internet.
ignore all sites that relate to car or home hi-fi audio.
| |
| Alexander 2005-07-30, 6:21 pm |
| Op [GMT+1=CET], hakte Jamie op ons in met:
> John Fields wrote:
>
> i am glad some one is on the ball here! )
Damn perhaps Maxwell can help us out ;)
| |
| John Fields 2005-07-30, 6:21 pm |
| On Sat, 30 Jul 2005 02:14:28 -0400, "TimPerry"
<timperry@noaspamadelphia.net> wrote:
>
>"AllTel - Jim Hubbard" <reply@newsgroups.com> wrote in message
>news:232f7$42eaf0d2$97d59ba4$23531@ALLTEL.NET...
>electrical
>
>neither
---
That's not true. The electrons diffusing through the flattened
portion of the wire would result in a charge flow profile more like
Figure B, given the understanding that none of the electrons would
follow a straight-line path through any portion of the wire.
Further, the assumption is made that the cross-sectional area of the
wire remains constant at the connection.
---
>... research "skin effect"
---
To what end? Skin effect comes into play when the current in the
wire is alternating.
--
[color=darkred]
--
John Fields
Professional Circuit Designer
| |
| John Fields 2005-07-30, 7:21 pm |
| On Sat, 30 Jul 2005 10:50:24 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>
>
>
>Hmmm...
>
>Copper does have a weak Hall effect. And the current through a round
>wire does make a circular/transverse magnetic field. So, at very high
>DC currents, is the current density a bit non-uniform?
---
I would think that simple thermal effects would cause charge to flow
closer to the surface just because that part of the conductor would
be cooler, ergo lower resistance than the hotter interior.
--
John Fields
Professional Circuit Designer
| |
|
|
| Alltel - Jim Hubbard 2005-07-31, 3:21 am |
| Thanks to everyone for the great input!
| |
| Jasen Betts 2005-07-31, 7:21 am |
| In article <xPMGe.110096$wr.102342@clgrps12>, JoeSixPack wrote:
> Before you attack this post, saying electrons can only travel at the speed
> of light, that's incorrect. The electrons themselves can travel any speed,
> but the voltage wave produced does travel at 300,000 kms per second.
electrons cannot exceed the speed of light in a vacuum. no physical object can.
That said the drift velocity of electrons in electric wires is rarely
more than walking speed, the signals are transmitted by the interaction
of the electrons electric fields - ie each electron pushes on its neighbours...
signals usually seem to propogate through coaxial conductors at 2/3 the
speed of light. iirc they travel no faster in any other type of conductor.
Even in fibreoptic cables the signals (photons) go slower than 300000 km/s
the ratio difference is the definition of the refractive index of the optic
material.
--
Bye.
Jasen
| |
| John Fields 2005-07-31, 8:21 am |
| On 30 Jul 2005 18:26:41 -0700, "Autymn D. C."
<lysdexia@sbcglobal.net> wrote:
>John Fields wrote:
>
>wrong:
>http://groups.google.com/group/sci....31738a7b007dc8c
---
Wrong.
Since an electron has a rest mass, m0, and since:
m0
mr = -------------------- ,
sqrt (1 - (v²/c²))
its relativistic mass, mr, will tend toward infinity as its
velocity, v, approaches that of light, c.
--
John Fields
Professional Circuit Designer
| |
| DBLEXPOSURE 2005-07-31, 1:21 pm |
|
"Repeating Rifle" <salmonegg@sbcglobal.net> wrote in message
news:BF106651.18F2%salmonegg@sbcglobal.net...
> On 7/29/05 8:15 PM, in article 232f7$42eaf0d2$97d59ba4$23531@ALLTEL.NET,
> "AllTel - Jim Hubbard" <reply@newsgroups.com> wrote:
>
>
> <snip>
>
> It is not a stupid question--it is just irrelevant. Current flows in
> various
> ways, and in almost all cases, the details of the flow is unimportant. The
> "wires" can be made from metals, semimetals, hot glass, semiconductors,
> ionic solutions, etc. Each has a different kind of conduction mechanism.
>
> I have taken the probably impossible task upon myself to discourage
> thinking
> of conduction as a flow of electrons.
>
> Bill
>
Not so impossible. I think many think of the electron as some little
microscopic BB with a negative charge. It may be more accurate to think of
the buggers as a microscopic region of space/time with properties that give
it a negative charge among other properties. It takes an enormous amount of
mass to move space/time. It is the properties that are passed along the
way. A bit of an illusion perhaps.
So yes, I agree, not a flow of electrons but a flow of energy...
Whatever that is.....
It is all speculation of course. I have never seen an electron, Have you?
I don't think we should judge the OP on the relevancy of his question, as we
have no idea why he asked it...
| |
| JoeSixPack 2005-07-31, 4:21 pm |
|
"Autymn D. C." <lysdexia@sbcglobal.net> wrote in message
news:1122773201.589083.190250@f14g2000cwb.googlegroups.com...
> John Fields wrote:
>
> wrong:
> http://groups.google.com/group/sci....31738a7b007dc8c
>
We are indeed gifted to have so many brainiacs in here.
| |
| Autymn D. C. 2005-08-01, 9:21 am |
| John Fields wrote:
> On 30 Jul 2005 18:26:41 -0700, "Autymn D. C."
> <lysdexia@sbcglobal.net> wrote:
>
5f7c447d531c53f5/f31738a7b007dc8c?lnk=3Dst&rnum=3D1#f31738a7b007dc8c[color=darkred]
>
> ---
> Wrong.
>
> Since an electron has a rest mass, m0, and since:
>
>
> m0
> mr =3D -------------------- ,
> sqrt (1 - (v=B2/c=B2))
>
>
> its relativistic mass, mr, will tend toward infinity as its
> velocity, v, approaches that of light, c.
> --
> John Fields
> Professional Circuit Designer
Read my proof or shut up. You do not even know what "tend" intends.
-Aut
| |
|
|
| Dimitrios Tzortzakakis 2005-08-01, 10:21 am |
|
--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "Alexander" <electricdummy@hotmail.com> Ýãñáøå óôï ìÞíõìá
news:dcfqoa$dbo$1@news1.zwoll1.ov.home.nl...
>
> "TimPerry" <timperry@noaspamadelphia.net> schreef in bericht
> news:WrqdndPloplTh3bfRVn-3w@adelphia.com...
the[color=darkred]
>
> Most of the times this just aplies to AC (high frequency) circuits
Or of line-to-line voltage equal or above 220 kV.Therefore transmission
lines of 400 kV are always designed with a double conductor, thus to reduce
the corona discharge due to skin effect.
determined[color=darkred]
decreasing[color=darkred]
>
>
| |
| Dimitrios Tzortzakakis 2005-08-01, 11:21 am |
|
--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> ?????? ???
?????? news:e9fne1prvtm2kc09q8c0123i3479hra1ek@4ax.com...
> On Sat, 30 Jul 2005 09:39:58 -0700, John Larkin
> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>
>
>
> Hmmm...
>
> Copper does have a weak Hall effect. And the current through a round
> wire does make a circular/transverse magnetic field. So, at very high
> DC currents, is the current density a bit non-uniform?
>
Very high AC currents are much more common.The output of a moderate 300 MW
alternator is 10 kA at 21 kV.A nuclear power station alternator with a
voltage of 27 kV almost reaches 20kA, with a nominal power output of 1500
MVA.Always talking about balanced three-phase systems.The output of the 300
MW power-station at 400 kV transmission voltage is just 400 A.Conductors in
all LV circuits are made of electroletically purified solid copper, 99,99 %
Cu.In MV, HV and EHV distribution and transimission voltages respectively,
they use ACSR conductors (Aluminium Conductor Steel Reinforced)that have a
steel core, but an aluminium outer sheath.
| |
| Dimitrios Tzortzakakis 2005-08-01, 11:21 am |
|
--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "John Fields" <jfields@austininstruments.com> ?????? ??? ??????
news:tbune11gjuu0qst4fv4446d89ejojeu1rq@4ax.com...
> On Sat, 30 Jul 2005 10:50:24 -0700, John Larkin
> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>
>
> ---
> I would think that simple thermal effects would cause charge to flow
> closer to the surface just because that part of the conductor would
> be cooler, ergo lower resistance than the hotter interior.
That can happen in high impulse short circuit currents.An unfused 220 V
circuit shortcircuited between live and earth, can have an impulse current
of 20 kA.Properly fused with a circuit breaker, up to 50 A.In normal
operating conditions, a transmission line of 150 kV operating at 200 A with
an ambient teperature of 20 deg.C (65deg.F)should not exceed 50
deg.C(105deg.F)however as it operates continually at these conditions the
temperature is uniform across the conductor (ACSR).
| |
| John Fields 2005-08-01, 11:21 am |
| On 1 Aug 2005 04:44:24 -0700, "Autymn D. C."
<lysdexia@sbcglobal.net> wrote:
>John Fields wrote:
>
>Read my proof or shut up. You do not even know what "tend" intends.
---
I see. Instead of reason, you prefer insult.
I will neither read your "proof" nor will I shut up, and if you
don't like it, you miserable son of a XXXXX, you can go fuck
yourself.
--
John Fields
Professional Circuit Designer
| |
| John Fields 2005-08-01, 1:21 pm |
|
John Fields wrote:
I would think that simple thermal effects would cause charge to flow
closer to the surface just because that part of the conductor would
be cooler, ergo lower resistance than the hotter interior.
To which Tzortzakakis Dimitrios replied:
That can happen in high impulse short circuit currents.An unfused
220 V
circuit shortcircuited between live and earth, can have an impulse
current
of 20 kA.Properly fused with a circuit breaker, up to 50 A.In normal
operating conditions, a transmission line of 150 kV operating at 200
A with
an ambient teperature of 20 deg.C (65deg.F)should not exceed 50
deg.C(105deg.F)however as it operates continually at these
conditions the
temperature is uniform across the conductor (ACSR).
---
I think you misunderstood my point, which was that the copper at the
surface of the conductor would, by virtue of radiation and
convection, be cooler than the copper at the center of the
conductor. Such being the case, the resistance of the cooler copper
at the surface would be less than the resistance of the copper in
the core, leading to a non-uniform radial current gradient in the
conductor.
--
John Fields
Professional Circuit Designer
| |
| Alexander 2005-08-01, 2:21 pm |
|
"Dimitrios Tzortzakakis" <dimtzort@otenet.gr> schreef in bericht
news:dcl731$u0$1@usenet.otenet.gr...
>
>
> --
> Tzortzakakis Dimitrios
> major in electrical engineering, freelance electrician
> FH von Iraklion-Kreta, freiberuflicher Elektriker
> dimtzort AT otenet DOT gr
> Ï "Alexander" <electricdummy@hotmail.com> Ýãñáøå óôï ìÞíõìá
> news:dcfqoa$dbo$1@news1.zwoll1.ov.home.nl...
> the
> Or of line-to-line voltage equal or above 220 kV.Therefore transmission
> lines of 400 kV are always designed with a double conductor, thus to
> reduce
> the corona discharge due to skin effect.
A tranismission line always has an AC element according to fourier Analysis.
Some times it is superimposed on an DC element but nearly always you want to
avoid this.
> determined
> decreasing
>
>
| |
| Alexander 2005-08-01, 2:21 pm |
|
"Dimitrios Tzortzakakis" <dimtzort@otenet.gr> schreef in bericht
news:dcl7ei$2f1$1@usenet.otenet.gr...
>
>
> --
> Tzortzakakis Dimitrios
> major in electrical engineering, freelance electrician
> FH von Iraklion-Kreta, freiberuflicher Elektriker
> dimtzort AT otenet DOT gr
> ? "John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> ?????? ???
> ?????? news:e9fne1prvtm2kc09q8c0123i3479hra1ek@4ax.com...
> Very high AC currents are much more common.The output of a moderate 300 MW
> alternator is 10 kA at 21 kV.A nuclear power station alternator with a
> voltage of 27 kV almost reaches 20kA, with a nominal power output of 1500
> MVA.Always talking about balanced three-phase systems.The output of the
> 300
> MW power-station at 400 kV transmission voltage is just 400 A.Conductors
> in
> all LV circuits are made of electroletically purified solid copper, 99,99
> %
> Cu.In MV, HV and EHV distribution and transimission voltages respectively,
> they use ACSR conductors (Aluminium Conductor Steel Reinforced)that have a
> steel core, but an aluminium outer sheath.
>
Sometimes you have something like Aluminium inside (for the weight) and
Cupper on the outside for conductivity. Due to the Skin Effect this is where
the most (AC) current will flow.
On some application I have even seen Cu on the inside and Au on the outside,
my guess there is at least one other material between the two for obvious
reasons.
Alexander (ACE, Applied Communications Engineer)
| |
| John Fields 2005-08-01, 8:21 pm |
| On Mon, 1 Aug 2005 18:23:25 +0200, "Alexander"
<electricdummy@hotmail.com> wrote:
>Sometimes you have something like Aluminium inside (for the weight) and
>Cupper on the outside for conductivity. Due to the Skin Effect this is where
>the most (AC) current will flow.
>On some application I have even seen Cu on the inside and Au on the outside,
>my guess there is at least one other material between the two for obvious
>reasons.
Really? The reasoning for that layering doesn't seem obvious to me,
so would you mind explaining it in greater detail?
--
John Fields
Professional Circuit Designer
| |
| daestrom 2005-08-01, 10:21 pm |
|
"Dimitrios Tzortzakakis" <dimtzort@otenet.gr> wrote in message
news:dcl731$u0$1@usenet.otenet.gr...
>
>
> --
> Tzortzakakis Dimitrios
> major in electrical engineering, freelance electrician
> FH von Iraklion-Kreta, freiberuflicher Elektriker
> dimtzort AT otenet DOT gr
> Ï "Alexander" <electricdummy@hotmail.com> Ýãñáøå óôï ìÞíõìá
> news:dcfqoa$dbo$1@news1.zwoll1.ov.home.nl...
> the
> Or of line-to-line voltage equal or above 220 kV.Therefore transmission
> lines of 400 kV are always designed with a double conductor, thus to
> reduce
> the corona discharge due to skin effect.
Oh boy, you have a 'couple of crossed wires' there.
"Skin effect" is the phenomenon where electric current flow is forced out
from the center of a conductor due to the self-inductance in the conductor
when carrying AC current. The higher the frequency, the more pronounced the
current shift to the exterior. It's mostly a problem with high current
situations, even if the voltages are so low that corona discharge is not a
problem.
"Corona discharge" is *NOT* caused by AC or skin effect. Corona discharge
is caused by a high voltage gradient in the space around a conductor. This
is a combination of the voltage applied to the conductor and the effective
radius of the conductor. A high voltage, or very small effective radius can
increase the gradient to the point where the air is ionized. Simple proof
is that corona discharge is a problem with high DC voltage systems as well
as AC.
Sometimes hollow tubes are used for high frequency power conductors. This
reduces the weight and cost by eliminating the central part of the
conductor, where 'skin effect' has rendered the impedence high anyway. So
little admittance is lost for a great savings in material/weight.
And for high voltage systems, multiple parallel conductors are used to give
a larger 'effective radius', thereby reducing the corona losses.
But the two phenomenon are not related, and the two techniques used are not
really related.
daestrom
| |
| daestrom 2005-08-01, 10:21 pm |
|
"John Fields" <jfields@austininstruments.com> wrote in message
news:tbune11gjuu0qst4fv4446d89ejojeu1rq@4ax.com...
> On Sat, 30 Jul 2005 10:50:24 -0700, John Larkin
> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>
>
> ---
> I would think that simple thermal effects would cause charge to flow
> closer to the surface just because that part of the conductor would
> be cooler, ergo lower resistance than the hotter interior.
>
An interesting point. *IF* the current density is uniform across the
conductor, then the heat generated would be uniform in each unit
cross-section. And a uniform heat generation in a cylindrical rod leads to
a parabolic temperature profile, the highest exactly at the centerline,
dropping of as you move outward along any radial line.
Of course, in an AC line, the current density isn't uniform, so neither is
the heat generation. So when it comes to skin effect, it tends to lower the
peak, centerline temperature.
Now, given that both copper and aluminum are excellent heat conductors, it
might be interesting to calculate how big a temperature profile could be
expected, and from this calculate the variation in resistivity.
I suspect the work has been done before, and that the difference is rather
modest for all but the largest cylindrical conductors.
daestrom
> --
> John Fields
> Professional Circuit Designer
| |
| daestrom 2005-08-01, 10:21 pm |
|
"Dimitrios Tzortzakakis" <dimtzort@otenet.gr> wrote in message
news:dcl7ei$2f1$1@usenet.otenet.gr...
>
>
> --
> Tzortzakakis Dimitrios
> major in electrical engineering, freelance electrician
> FH von Iraklion-Kreta, freiberuflicher Elektriker
> dimtzort AT otenet DOT gr
> ? "John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> ?????? ???
> ?????? news:e9fne1prvtm2kc09q8c0123i3479hra1ek@4ax.com...
> Very high AC currents are much more common.The output of a moderate 300 MW
> alternator is 10 kA at 21 kV.A nuclear power station alternator with a
> voltage of 27 kV almost reaches 20kA, with a nominal power output of 1500
> MVA.
Yes, but most of the phase conductors that I've seen from large alternators
(500MW to 1200MW) to the step-up transformers are not simple round
conductors. In fact, rectangular tubing is used for the conductors (at
least those used in many nuclear stations). The tube is encased within an
outer 'pipe' and H2 is forced down the center of the tube to the end, where
it exits the tube and returns outside the tube within the outer pipe. Such
'isophase busses' are specifically designed to carry this large amount of
current just far enough to reach the main step-up transformer where it rises
from the nominal 25kv to 345kv or higher. The secondary is connected with
'normal' ACRS conductor to the remaining switch yard equipment.
daestrom
| |
| TokaMundo 2005-08-02, 12:21 am |
| On Tue, 02 Aug 2005 00:45:43 GMT, "daestrom"
<daestrom@NO_SPAM_HEREtwcny.rr.com> Gave us:
>
>"John Fields" <jfields@austininstruments.com> wrote in message
>news:tbune11gjuu0qst4fv4446d89ejojeu1rq@4ax.com...
>
>An interesting point. *IF* the current density is uniform across the
>conductor, then the heat generated would be uniform in each unit
>cross-section. And a uniform heat generation in a cylindrical rod leads to
>a parabolic temperature profile, the highest exactly at the centerline,
>dropping of as you move outward along any radial line.
>
>Of course, in an AC line, the current density isn't uniform, so neither is
>the heat generation. So when it comes to skin effect, it tends to lower the
>peak, centerline temperature.
>
>Now, given that both copper and aluminum are excellent heat conductors, it
>might be interesting to calculate how big a temperature profile could be
>expected, and from this calculate the variation in resistivity.
>
>I suspect the work has been done before, and that the difference is rather
>modest for all but the largest cylindrical conductors.
For AC at this frequency there is nil skin effect.
Current in a wire will heat the wire evenly if it is of one
material. a cladded conductor will disperse heat according to the
thermal and electrical conductivities of the mediums that make up the
wire.
A copper cladded aluminum wire (never seen it) will heat more
inside as aluminum has poorer electrical conductivity and nearly
identical thermal conductivities. The result will *still* be even
heating for the most part.
An Aluminum cladded Copper conductor will heat evenly as the
differences are so slight as to make no difference.
| |
| TokaMundo 2005-08-02, 12:21 am |
| On Tue, 02 Aug 2005 00:45:43 GMT, "daestrom"
<daestrom@NO_SPAM_HEREtwcny.rr.com> Gave us:
>
>"Dimitrios Tzortzakakis" <dimtzort@otenet.gr> wrote in message
>news:dcl731$u0$1@usenet.otenet.gr...
>
>Oh boy, you have a 'couple of crossed wires' there.
>
>"Skin effect" is the phenomenon where electric current flow is forced out
>from the center of a conductor due to the self-inductance in the conductor
>when carrying AC current. The higher the frequency, the more pronounced the
>current shift to the exterior. It's mostly a problem with high current
>situations, even if the voltages are so low that corona discharge is not a
>problem.
It becomes more prevalent as frequency goes up, not current.
>
>"Corona discharge" is *NOT* caused by AC or skin effect. Corona discharge
>is caused by a high voltage gradient in the space around a conductor. This
>is a combination of the voltage applied to the conductor and the effective
>radius of the conductor. A high voltage, or very small effective radius can
>increase the gradient to the point where the air is ionized. Simple proof
>is that corona discharge is a problem with high DC voltage systems as well
>as AC.
>
>Sometimes hollow tubes are used for high frequency power conductors. This
>reduces the weight and cost by eliminating the central part of the
>conductor, where 'skin effect' has rendered the impedence high anyway. So
>little admittance is lost for a great savings in material/weight.
VERY high frequency. NOT AC line frequencies.
| |
| John Larkin 2005-08-02, 1:21 am |
| On Tue, 02 Aug 2005 03:00:06 GMT, TokaMundo <TokaMundo@weedizgood.org>
wrote:
>
> VERY high frequency. NOT AC line frequencies.
Not so. At 60 Hz, copper skin depth is about 0.85 cm.
John
| |
| DBLEXPOSURE 2005-08-02, 1:21 am |
|
"John Fields" <jfields@austininstruments.com> wrote in message
news:cj8se15th0rnin0p86q8nhl4s2li0pgh5g@4ax.com...
> On 1 Aug 2005 04:44:24 -0700, "Autymn D. C."
> <lysdexia@sbcglobal.net> wrote:
>
>
> ---
> I see. Instead of reason, you prefer insult.
>
> I will neither read your "proof" nor will I shut up, and if you
> don't like it, you miserable son of a XXXXX, you can go fuck
> yourself.
>
> --
> John Fields
> Professional Circuit Designer
Any math that results in infinity might be fundamentally flawed. Infinity
is a mathematical impossibility. No mathematical functions can be performed
on infinity. It cannot be divided, multiplied, added to or subtracted from.
It is a non-quantity. Therefore, can it be a solution to an equation?
Just as Newton's equations where once considered mathematical law, until
professor Einstein proved otherwise, Einstein's theories may also someday be
shown to be incomplete.
It is possible that when an electron or photon reaches Einstein's cosmic
speed limit something entirely different happens than what the currently
accepted math would tell us is happening.
It may very well be that electrons can and do travel at speeds faster than C
but we cannot observe nor comprehend what happens at this point.
So for practical reasons, I must agree with Fields. But for philosophical
reasons, I must agree Auytm. However, none of you have the answer so it is
silly to stake out some absolute ground.. Is better to dream about it.
Exuse me for now I must return to my game, rolling dice with God. It seems
every time I get up on him he changes the rules.........
Herr Fields, wünsche ich, daß Sie das Verwenden solcher Geflügelsprache im
allgemeinen Forum nehmen würden.
Fale não com o tounge do diabo
| |
| Don Bowey 2005-08-02, 2:21 am |
| On 8/1/05 8:00 PM, in article vdote1tb8oed91mpoiqsa0pag4s4lclrnm@4ax.com,
"TokaMundo" <TokaMundo@weedizgood.org> wrote:
> On Tue, 02 Aug 2005 00:45:43 GMT, "daestrom"
> <daestrom@NO_SPAM_HEREtwcny.rr.com> Gave us:
>
>
> It becomes more prevalent as frequency goes up, not current.
>
>
> VERY high frequency. NOT AC line frequencies.
Define "VERY." Is that higher than Very and very?
Skin effect is measurable in cables at as low as 100 kHz.
Don
| |
| Alexander 2005-08-02, 2:21 am |
|
"John Fields" <jfields@austininstruments.com> schreef in bericht
news:enate1tkhlkv8gajkdjbjq7u3guvkkokno@4ax.com...
> On Mon, 1 Aug 2005 18:23:25 +0200, "Alexander"
> <electricdummy@hotmail.com> wrote:
>
>
>
> Really? The reasoning for that layering doesn't seem obvious to me,
> so would you mind explaining it in greater detail?
>
> --
> John Fields
> Professional Circuit Designer
If you connect Au to Cu and put a Current through it, for best results AC,
the Cu starts corroding at the transistion from Cu to Au. This is always the
case when putting to metals together, the greater the difference between the
metals the faster the corroding will be.
| |
| Alexander 2005-08-02, 2:21 am |
|
"Alexander" <electricdummy@hotmail.com> schreef in bericht
news:dcmtj7$a9d$1@news4.zwoll1.ov.home.nl...
>
> "John Fields" <jfields@austininstruments.com> schreef in bericht
> news:enate1tkhlkv8gajkdjbjq7u3guvkkokno@4ax.com...
>
> If you connect Au to Cu and put a Current through it, for best results AC,
> the Cu starts corroding at the transistion from Cu to Au. This is always
> the case when putting to metals together, the greater the difference
> between the metals the faster the corroding will be.
>
This is also the reason why silver and gold contacts should never be
soldered with normal Sn63Pb37 solderwire
| |
| John Fields 2005-08-02, 7:21 am |
| On Tue, 2 Aug 2005 06:42:29 +0200, "Alexander"
<electricdummy@hotmail.com> wrote:
>If you connect Au to Cu and put a Current through it, for best results AC,
>the Cu starts corroding at the transistion from Cu to Au. This is always the
>case when putting to metals together, the greater the difference between the
>metals the faster the corroding will be.
---
That's not true.
--
John Fields
Professional Circuit Designer
| |
| Dimitrios Tzortzakakis 2005-08-02, 10:21 am |
|
--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> Ýãñáøå óôï ìÞíõìá
news:XmzHe.1962$Rc6.702@twister.nyroc.rr.com...
>
> "Dimitrios Tzortzakakis" <dimtzort@otenet.gr> wrote in message
> news:dcl731$u0$1@usenet.otenet.gr...
>
> Oh boy, you have a 'couple of crossed wires' there.
>
> "Skin effect" is the phenomenon where electric current flow is forced out
> from the center of a conductor due to the self-inductance in the conductor
> when carrying AC current. The higher the frequency, the more pronounced
the
> current shift to the exterior. It's mostly a problem with high current
> situations, even if the voltages are so low that corona discharge is not a
> problem.
>
> "Corona discharge" is *NOT* caused by AC or skin effect. Corona discharge
> is caused by a high voltage gradient in the space around a conductor.
This
> is a combination of the voltage applied to the conductor and the effective
> radius of the conductor. A high voltage, or very small effective radius
can
> increase the gradient to the point where the air is ionized. Simple proof
> is that corona discharge is a problem with high DC voltage systems as well
> as AC.
>
> Sometimes hollow tubes are used for high frequency power conductors. This
> reduces the weight and cost by eliminating the central part of the
> conductor, where 'skin effect' has rendered the impedence high anyway. So
> little admittance is lost for a great savings in material/weight.
>
> And for high voltage systems, multiple parallel conductors are used to
give
> a larger 'effective radius', thereby reducing the corona losses.
>
> But the two phenomenon are not related, and the two techniques used are
not
> really related.
>
Yes, but also in voltages >=15 kV there's a signifigant skin effect, that's
why all transmission conductors are constructed with a steel *core* and an
*aluminium* outer sheath, because the current tends to flow on the skin of
the conductor.I mentioned corona discharge, to bring into evidence the very
strong electric field around the conductor in very high voltages.
>daestrom
>
>
| |
| Alexander 2005-08-02, 12:21 pm |
| Op [GMT+1=CET], hakte John Fields op ons in met:
> On Tue, 2 Aug 2005 06:42:29 +0200, "Alexander"
> <electricdummy@hotmail.com> wrote:
>
>
>
> ---
> That's not true.
You're right it needs also an electrlyt which is most of the times present.
| |
| John Larkin 2005-08-02, 12:21 pm |
| On Tue, 02 Aug 2005 02:57:11 GMT, TokaMundo <TokaMundo@weedizgood.org>
wrote:
>
> For AC at this frequency there is nil skin effect.
>
Not nil. Do the math.
John
| |
| DBLEXPOSURE 2005-08-02, 1:21 pm |
|
"John Fields" <jfields@austininstruments.com> wrote in message
news:4ofue1lca6tpqat9iqvepk6dhplv1v9335@4ax.com...
> On Tue, 2 Aug 2005 06:42:29 +0200, "Alexander"
> <electricdummy@hotmail.com> wrote:
>
>
>
> ---
> That's not true.
>
> --
> John Fields
> Professional Circuit Designer
Firstly, Aluminium is Al not Au. Au is gold. You are speaking of
aluminium and coper?
Galvanic Corrosion Is possible when Al and Cu are in contact with one and
other. If I recal correctly a dialectric such as water needs to be present.
Cathodic protection, (electric current) can be used to slow or stop this
proccess. I Imagine reversing the polarity may speed it up. Aluminium is
the "Less Nobel" of the two metals so I would imagine that it would be the
one to corrode.
| |
| Alexander 2005-08-02, 2:21 pm |
| Op [GMT+1=CET], hakte DBLEXPOSURE op ons in met:
> "John Fields" <jfields@austininstruments.com> wrote in message
> news:4ofue1lca6tpqat9iqvepk6dhplv1v9335@4ax.com...
>
> Firstly, Aluminium is Al not Au. Au is gold. You are speaking of
> aluminium and coper?
>
> Galvanic Corrosion Is possible when Al and Cu are in contact with one
> and other. If I recal correctly a dialectric such as water needs to
> be present. Cathodic protection, (electric current) can be used to
> slow or stop this proccess. I Imagine reversing the polarity may
> speed it up. Aluminium is the "Less Nobel" of the two metals so I
> would imagine that it would be the one to corrode.
Correct I also added the remark of the diëlectricum to the discussion.
And your remark about Aluminium is correct, however as stated in some
applications I have seen an Copper core and an Gold (aurum) shell. And since
the combination gold-copper is worse then the well known combination
aluminium-copper.
But at least ThanX for confirming my statement and not saying its not true
without giving a reason as someone else did.
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Mon, 01 Aug 2005 20:21:31 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>On Tue, 02 Aug 2005 03:00:06 GMT, TokaMundo <TokaMundo@weedizgood.org>
>wrote:
>
>
>
>
>Not so. At 60 Hz, copper skin depth is about 0.85 cm.
Did you even look at that number? That is 8.5 mm!
No? OK. So for all practical purposes that do not have 20 cm wire
involved (ie any normal residential application) there is NO skin
effect! Where in everyday life does a person use wire that has a
diameter greater than 8.5 mm that would present anything other than
100% current density in the conductor? The wave is just too slow for
anything other than full propagation. Hell, even a 25kW transformer
won't see any difference.
In ohms per foot DC or AC at 60Hz the value is the same for all wire
diameters that have a gauge number.
Before any difference could even be noted, the wired diameter would
have to be over 16 mm.
What part of the word negligible, or not of any effect do you not
understand?
http://www.bcae1.com/trnsfrmr.htm
If you'll read down the page to the skin depth calculators, you'll
see that the ohms per foot (the only value that matters here) is the
same for any gauge wire put into the calculator fields.
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Mon, 01 Aug 2005 21:28:10 -0700, Don Bowey <dbowey@comcast.net>
Gave us:
>On 8/1/05 8:00 PM, in article vdote1tb8oed91mpoiqsa0pag4s4lclrnm@4ax.com,
>"TokaMundo" <TokaMundo@weedizgood.org> wrote:
>
>
>Define "VERY." Is that higher than Very and very?
Your logic varies.
>
>Skin effect is measurable in cables at as low as 100 kHz.
>
>Don
Tell us, guru don, where does 100kHz get used as an AC power line
frequency?
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Tue, 02 Aug 2005 04:41:38 -0500, John Fields
<jfields@austininstruments.com> Gave us:
>On Tue, 2 Aug 2005 06:42:29 +0200, "Alexander"
><electricdummy@hotmail.com> wrote:
>
>
>
>---
>That's not true.
It's called galvanic reaction.
The Navy seems to think it's real. Does that make you an idiot?
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Tue, 2 Aug 2005 15:33:21 +0300, "Dimitrios Tzortzakakis"
<dimtzort@otenet.gr> Gave us:
>Yes, but also in voltages >=15 kV there's a signifigant skin effect,
Wrong! Skin effect is a function of frequency, not voltage. The
reason YOU think there is a significant skin effect is likely due to
the method at which your "15kV" source was generated.
That being likely a high frequency switcher or oscillator.
> that's
>why all transmission conductors are constructed with a steel *core* and an
>*aluminium* outer sheath,
No, it isn't. FREQUENCY is the reason. The other reason steel
cores are used is due to the fact that transmission lines are
typically hung from between two points separated by some great
distance such that the wire itself needs to be able to support the
weight of itself. The steel cores are there to increase the tensile
strength of the overall transmission line. This is a reference to
high frequency RF transmission lines. For power lines, steel is used
for the same, tensile increasing reason. The cladding is used to
reduce the ohms per foot of the strand. At 60Hz, however, the skin
effect hovers near NIL.
> because the current tends to flow on the skin of
>the conductor.
That is 100% dependent upon frequency.
http://www.bcae1.com/trnsfrmr.htm
>I mentioned corona discharge, to bring into evidence the very
>strong electric field around the conductor in very high voltages.
Corona is a function of voltage and the capacity for air to ionize.
How much corona is on a wire in oil that carries a high voltage AC or
DC? Same wire in air?
Electric fields increase with current in a wire. Look at a quarter
shrinker. Low voltage, high current, huge field.
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Tue, 02 Aug 2005 08:06:25 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>On Tue, 02 Aug 2005 02:57:11 GMT, TokaMundo <TokaMundo@weedizgood.org>
>wrote:
>
>
>
>
>Not nil. Do the math.
>
Very much so as close to nil as it gets. Review the math.
http://www.bcae1.com/trnsfrmr.htm
That's just one source.
| |
| Owamanga 2005-08-02, 3:21 pm |
| On Tue, 02 Aug 2005 17:40:35 GMT, TokaMundo <TokaMundo@weedizgood.org>
wrote:
> Corona is a function of voltage and the capacity for air to ionize.
Wow, and I thought it was a Mexican beer that tastes so bad you have
to add lime to it before consumption.
--
Owamanga!
http://www.pbase.com/owamanga
| |
| John Larkin 2005-08-02, 3:21 pm |
| On Tue, 02 Aug 2005 17:24:34 GMT, TokaMundo <TokaMundo@weedizgood.org>
wrote:
>On Mon, 01 Aug 2005 20:21:31 -0700, John Larkin
><jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>
> Did you even look at that number? That is 8.5 mm!
>
Not only did I look at it, but I calculated it, and typed it.
> No? OK. So for all practical purposes that do not have 20 cm wire
>involved (ie any normal residential application) there is NO skin
>effect! Where in everyday life does a person use wire that has a
>diameter greater than 8.5 mm that would present anything other than
>100% current density in the conductor? The wave is just too slow for
>anything other than full propagation. Hell, even a 25kW transformer
>won't see any difference.
>
I just bought a building that has 3-phase, 800-amp service, and skin
effect certainly has affected the sizing of the main feeder wires. And
I work with people who build gigawatt 60 Hz power plants and jumbo-jet
400 Hz power systems. That's my "everyday life."
In big AC transmission lines, there's a complex optimization involving
wire weight, tensile strength, ohmic losses, skin effect, corona
losses, wire cost, and tower spacing/cost.
> In ohms per foot DC or AC at 60Hz the value is the same for all wire
>diameters that have a gauge number.
>
> Before any difference could even be noted, the wired diameter would
>have to be over 16 mm.
Not so. At 0.85 cm depth, current density is down to 1/e (ie, only
0.37 of) the surface density. That's pretty significant.
>
> What part of the word negligible, or not of any effect do you not
>understand?
I'm an engineer, so I consider something to be "negligable" if I can
demonstrate, quantitatively, that it doesn't matter enough to affect a
system. 37% is therefore worth a second look.
To speak in your style, what part of "doing the math" do you not
understand?
John
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Tue, 02 Aug 2005 17:43:16 GMT, Owamanga
<owamanga-not-this-bit@hotmail.com> Gave us:
>On Tue, 02 Aug 2005 17:40:35 GMT, TokaMundo <TokaMundo@weedizgood.org>
>wrote:
>
>
>Wow, and I thought it was a Mexican beer that tastes so bad you have
>to add lime to it before consumption.
And they have the nerve to call it a "specialty beer" here in So
Cal.
Just so the idiots can charge more for less!
Talk about misnomers!
Give me a Sam Adams or Chimay Gold ANYDAY!
Bass Ale... anything!
Sheesh Coors' "Killian's Red" is better than that Mexican crap!
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Tue, 02 Aug 2005 10:54:26 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>Not so. At 0.85 cm depth, current density is down to 1/e (ie, only
>0.37 of) the surface density. That's pretty significant.
0.85cm is 8.5 mm. That means that the wire has to be bigger than
that number as a radius before the current flow anywhere else besides
the entire wire.
So, again, if the wire is less than 17mm in diameter, there will be
no skin effect involved. You may note some other effects, but skin
effect won't be one of them.
| |
| TokaMundo 2005-08-02, 3:21 pm |
| On Tue, 02 Aug 2005 10:54:26 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>I'm an engineer, so I consider something to be "negligable" if I can
>demonstrate, quantitatively, that it doesn't matter enough to affect a
>system.
No shit.
> 37% is therefore worth a second look.
Your application of your "math" is what needs a second look.
>To speak in your style, what part of "doing the math" do you not
>understand?
What part of "you did the math wrong" do you not understand?
Before it would make a difference, the wire will have to be pretty
big (over 17mm diameter) , and before it will make a 37% difference,
it would have to be bigger still! Real simple math, there.
| |
| Bob Myers 2005-08-02, 4:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:v4cve15bd0ar0d02f0da10fbm87640sr98@4ax.com...
>
> Very much so as close to nil as it gets. Review the math.
I'm afraid you've got a pretty limited notion as to what "nil" would
be. Remember, with AC, one of the big concerns is the transmission
of significant amounts of power over long distances - have you thought
about how large those sorts of conductors ARE?
Bob M.
| |
| Bob Myers 2005-08-02, 4:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:i2dve15rqf7183m844bjidvu0v98rn9cjf@4ax.com...
> On Tue, 02 Aug 2005 10:54:26 -0700, John Larkin
> <jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>
>
> 0.85cm is 8.5 mm. That means that the wire has to be bigger than
> that number as a radius before the current flow anywhere else besides
> the entire wire.
Wrong again. You seem to think that the current is uniform
down to the "skin depth," and THEN it somehow starts to
fall off. As John already pointed out, with seemingly unwarranted
patience, that ain't so.
Once again: "do the math." And this time, go beyond just using
the skin-depth calculator on your favorite web site, and actually
figure out what the EFFECTS would be (in terms of resistive
loss, heating, whatever) of the skin depth at 60 Hz in a conductor
otherwise seemingly-properly-sized for the 800A service that
John mentioned as an example.
You might be surprised by the result.
Bob M.
| |
| DBLEXPOSURE 2005-08-02, 4:21 pm |
|
"Alexander" <electricdummy@hotmail.com> wrote in message
news:dco8pe$4nl$1@news2.zwoll1.ov.home.nl...
> Op [GMT+1=CET], hakte DBLEXPOSURE op ons in met:
>
>
> Correct I also added the remark of the diëlectricum to the discussion.
> And your remark about Aluminium is correct, however as stated in some
> applications I have seen an Copper core and an Gold (aurum) shell. And
> since the combination gold-copper is worse then the well known combination
> aluminium-copper.
>
> But at least ThanX for confirming my statement and not saying its not true
> without giving a reason as someone else did.
>
Your welcome, I thought you deserved a respectful reply...
| |
| TokaMundo 2005-08-02, 4:21 pm |
| On Tue, 02 Aug 2005 10:54:26 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>In big AC transmission lines, there's a complex optimization involving
>wire weight, tensile strength, ohmic losses, skin effect, corona
>losses, wire cost, and tower spacing/cost.
No shit.
For one thing, they are primarily designed for high tensile strength
as they have to stay mounted through all weather and environmental
conditions.
After that, their resistance is an issue as the primary material has
to be steel for the tensile forces involved. They usually get clad in
Aluminum as copper is too costly for such long runs, and the losses in
using aluminum are little in comparison. This is also the reason that
high voltages are used in long haul transmission lines. The loss
over 2000 feet of line with 120 volts on it is significantly different
than the loss over 2000 feet of line with 20,000 volts on it.
Corona will become a problem as that line voltage is raised. At
that time line spacing becomes an issue.
Tower spacing is a function of the terrain being traversed. Line
spacing ON a given tower design is a function only of the voltage that
is proposed to be carried, and the total number of conductors.
Skin effect, in these high tension line realms is only an issue if
the idiots that made the wire didn't know how deep to make the
cladding. If the wire is clad to thinly, there will be more loss as
the steel is more resistive, and the wire will heat more as well.
If it is clad too thickly, an unnecessary cost is introduced.
This is specifically because the skin depth is so deep at this
frequency, NOT due to it being a thin depth! So in power line cases,
the effect is an issue of how deep the cladding is, not how thin.
In RF transmission lines, which are typically nickel or silver
plated, it becomes a cost issue, and claddings are made as thin as
possible for a given application frequency. These cases are where one
will see hollow conductors, or plated tube or solids. This is where a
Litz configuration or plated conductor will assist one in design of a
circuit.
At 60Hz, a high voltage step up transformer will have some transfer
efficiency number. At switching frequencies, the same transformer
design (wire turn count wise) will operate better if the primary, and
or secondary have litz wire used in them as the effective resistance
of the winding will be reduced at the higher frequencies.
| |
| Bob Myers 2005-08-02, 4:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:mhbve1p34rfo2cpma8te55gjbgclte2a0j@4ax.com...
AC,[color=darkred]
the[color=darkred]
the[color=darkred]
>
> It's called galvanic reaction.
>
> The Navy seems to think it's real. Does that make you an idiot?
The Navy seems to think there's a significant problem with gold over
copper? Do tell....
Bob M.
| |
| TokaMundo 2005-08-02, 4:21 pm |
| On Tue, 02 Aug 2005 10:54:26 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>Not so. At 0.85 cm depth, current density is down to 1/e (ie, only
>0.37 of) the surface density. That's pretty significant.
0.85 cm is pretty thick. 8.5 mm in fact. Double that to get 17mm.
Unless the wire is larger than 17mm at 60Hz, the entire wire will
carry current. VERY simple math.
| |
| TokaMundo 2005-08-02, 4:21 pm |
| On Tue, 02 Aug 2005 18:35:31 GMT, "Bob Myers"
<nospamplease@address.invalid> Gave us:
>
>"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
>news:v4cve15bd0ar0d02f0da10fbm87640sr98@4ax.com...
>
>I'm afraid you've got a pretty limited notion as to what "nil" would
>be. Remember, with AC, one of the big concerns is the transmission
>of significant amounts of power over long distances - have you thought
>about how large those sorts of conductors ARE?
>
As I noted, the wire would have to be greater than 17mm in diameter.
A steel strand of 3/4 an inch covered with aluminum strands to a
finished thickness of an inch or so would be quite ideal. The entire
depth of the aluminum would carry the energy, and the steel would see
near none of it.
Coming back down to the consumer level, using any standard household
wire, the effect IS most certainly NIL. Even the 25 or 40kW
transformer hanging out on the pole has no need for any such
considerations.
If the wire feeding you house is over 17mm in diameter, there MIGHT
be a small difference in the ohmic resistance of the line. A very
small difference. Certainly not the 37% that was suggested.
| |
| TokaMundo 2005-08-02, 4:21 pm |
| On Tue, 02 Aug 2005 18:40:17 GMT, "Bob Myers"
<nospamplease@address.invalid> Gave us:
>
>"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
>news:i2dve15rqf7183m844bjidvu0v98rn9cjf@4ax.com...
>
>Wrong again. You seem to think that the current is uniform
>down to the "skin depth," and THEN it somehow starts to
>fall off.
No. What the figure tells one is where the current is near zero,
which is that area beneath the skin depth, all the way to the center
of the wire. The way the current passes through said skin depth area
doesn't matter.
> As John already pointed out, with seemingly unwarranted
>patience,
Try being less stupid. THAT is what is unwarranted here. Unless,
of course, it just comes naturally for you.
> that ain't so.
Whatever.
>Once again: "do the math." And this time, go beyond just using
>the skin-depth calculator on your favorite web site,
More stupidity. That was merely one location that I pointed out.
It explains it quite well, however, and much better than your
insulting XXX does.
> and actually
>figure out what the EFFECTS would be (in terms of resistive
>loss, heating, whatever) of the skin depth at 60 Hz in a conductor
>otherwise seemingly-properly-sized for the 800A service that
>John mentioned as an example.
Pure aluminum or pure copper runs will see no difference. The
reason that skin effect affects power transmission lines is due to the
lower conductivity cores that are typically used.
>
>You might be surprised by the result.
You might get along with folks, if you stop with the bullshit
insults. Sorry if YOU don't see your remarks that way, but I know
better. Both about the remarks, and the topic.
>
>Bob M.
| |
| TokaMundo 2005-08-02, 4:21 pm |
| On Tue, 02 Aug 2005 18:43:52 GMT, "Bob Myers"
<nospamplease@address.invalid> Gave us:
>
>"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
>news:mhbve1p34rfo2cpma8te55gjbgclte2a0j@4ax.com...
>
>AC,
>the
>the
>
>The Navy seems to think there's a significant problem with gold over
>copper? Do tell....
>
Look up Galvanic reaction in ship hulls, and you will find that all
Navy ships have provisions to reduce it.
Note again that my reference is to the effect, not the remarks about
specific elements. Learn to read.
| |
| John Fields 2005-08-02, 4:21 pm |
| On Tue, 2 Aug 2005 10:40:37 -0500, "DBLEXPOSURE"
<celstuff@hotmail.com> wrote:
>
>"John Fields" <jfields@austininstruments.com> wrote in message
>news:4ofue1lca6tpqat9iqvepk6dhplv1v9335@4ax.com...
>
>Firstly, Aluminium is Al not Au. Au is gold. You are speaking of
>aluminium and coper?
---
I doesn't make any difference, (but there is no metal named "coper",
so i'll assume you meant "copper") there won't be any corrosion
unless the dissimilar metals are in contact with each other in the
presence of an electrolyte, not a dielectric as you have stated.
>Galvanic Corrosion Is possible when Al and Cu are in contact with one and
>other. If I recal correctly a dialectric such as water needs to be present.
>Cathodic protection, (electric current) can be used to slow or stop this
>proccess. I Imagine reversing the polarity may speed it up. Aluminium is
>the "Less Nobel" of the two metals so I would imagine that it would be the
>one to corrode.
---
Less "noble", or more anodic.
If he truly meant a gold-copper couple, the copper, being more
anodic than gold, would corrode.
BTW, pure water _is_ a dielectric and dissimilar metals in contact
with each other and pure water would not corrode.\
--
John Fields
Professional Circuit Designer
| |
| DBLEXPOSURE 2005-08-02, 4:21 pm |
|
"John Fields" <jfields@austininstruments.com> wrote in message
news:ebfve1d9njtughtckfk1i3oqithcl1j1u1@4ax.com...
> On Tue, 2 Aug 2005 10:40:37 -0500, "DBLEXPOSURE"
> <celstuff@hotmail.com> wrote:
>
>
> ---
> I doesn't make any difference, (but there is no metal named "coper",
> so i'll assume you meant "copper") there won't be any corrosion
> unless the dissimilar metals are in contact with each other in the
> presence of an electrolyte, not a dielectric as you have stated.
>
>
> ---
> Less "noble", or more anodic.
>
> If he truly meant a gold-copper couple, the copper, being more
> anodic than gold, would corrode.
>
> BTW, pure water _is_ a dielectric and dissimilar metals in contact
> with each other and pure water would not corrode.\
>
> --
> John Fields
> Professional Circuit Designer
---
Less "noble", or more anodic.
---
Same difference
---
not a dielectric as you have stated
----
With the preface, "If I recal correctly", Correction noted.
---
(but there is no metal named "coper",
> so i'll assume you meant "copper")
---
BFD
| |
| John Fields 2005-08-02, 5:21 pm |
| On Tue, 2 Aug 2005 18:59:37 +0200, "Alexander"
<electricdummy@hotmail.com> wrote:
>Op [GMT+1=CET], hakte DBLEXPOSURE op ons in met:
>
>
>Correct I also added the remark of the diëlectricum to the discussion.
---
No you added the remark about the _electrolyte_, which was correct.
---
>And your remark about Aluminium is correct, however as stated in some
>applications I have seen an Copper core and an Gold (aurum) shell. And since
>the combination gold-copper is worse then the well known combination
>aluminium-copper.
---
In what way is it worse?
Looking at:
http://www.ocean.udel.edu/seagrant/.../corrosion.html
It seems that the distance between gold and copper (0.52V) is the
same as the distance between copper and aluminum, so why would the
rate of corrosion be worse for a gold-copper couple than for
copper-aluminum?
---
>But at least ThanX for confirming my statement and not saying its not true
>without giving a reason as someone else did.
---
Whether I gave a reason or not is unimportant, what matters is that
a factual error got corrected.
--
John Fields
Professional Circuit Designer
| |
| John Larkin 2005-08-02, 5:21 pm |
| On Tue, 02 Aug 2005 18:28:32 GMT, TokaMundo <TokaMundo@weedizgood.org>
wrote:
>On Tue, 02 Aug 2005 10:54:26 -0700, John Larkin
><jjlarkin@highNOTlandTHIStechnologyPART.com> Gave us:
>
>
> 0.85 cm is pretty thick. 8.5 mm in fact. Double that to get 17mm.
>
> Unless the wire is larger than 17mm at 60Hz, the entire wire will
>carry current. VERY simple math.
Current begins to fall off monotonically from the very surface for any
wire size at any AC frequency. There's no hard "skin boundary", and
the 1/e density is just a handy if arbitrary measurement point.
I don't see why this needs arguing over. In a given situation, you
just calculate the effects and decide how they affect things.
Sometimes a 200% increase in resistance doesn't matter, and sometimes
a 1% increase does. But skin effect does often matter in real
situations at 60 Hz, and shouldn't be always/automatically discounted.
John
| |
| John Fields 2005-08-02, 5:21 pm |
| On Tue, 02 Aug 2005 17:31:30 GMT, TokaMundo
<TokaMundo@weedizgood.org> wrote:
>On Tue, 02 Aug 2005 04:41:38 -0500, John Fields
><jfields@austininstruments.com> Gave us:
>
>
> It's called galvanic reaction.
>
> The Navy seems to think it's real. Does that make you an idiot?
---
Back looking for some more lumps, bonehead? OK, I'm happy to
oblige...
First, it's called "galvanic corrosion" and, second, if you knew
anything about it and had somehow managed to pull your head out of
your XXX before commenting, you might have noticed that the poster
made no mention of the electrolyte required for the corrosion to
occur. That's why what he said wasn't true.
--
John Fields
Professional Circuit Designer
| |
| John Fields 2005-08-02, 6:21 pm |
| On Tue, 2 Aug 2005 14:09:31 -0500, "DBLEXPOSURE"
<celstuff@hotmail.com> wrote:
>
>"John Fields" <jfields@austininstruments.com> wrote in message
>news:ebfve1d9njtughtckfk1i3oqithcl1j1u1@4ax.com...
>
>---
>Less "noble", or more anodic.
>---
>Same difference
---
Hardly. "Nobel" was the inventor of dynamite, while "noble", in the
context which makes sense in this thread, refers to chemical
inactivity.
---
>---
>not a dielectric as you have stated
>----
>
>With the preface, "If I recal correctly", Correction noted.
>
>---
>(but there is no metal named "coper",
>---
>BFD
---
Yup; wrong is wrong.
--
John Fields
Professional Circuit Designer
| |
| daestrom 2005-08-02, 7:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:vdote1tb8oed91mpoiqsa0pag4s4lclrnm@4ax.com...
> On Tue, 02 Aug 2005 00:45:43 GMT, "daestrom"
> <daestrom@NO_SPAM_HEREtwcny.rr.com> Gave us:
>
>
> It becomes more prevalent as frequency goes up, not current.
>
High currents do not increase skin effect, that is true. But the variation
in conductor admittance *caused* by skin effect is a larger problem with
high current conductors than it is with low current applications.
>
> VERY high frequency. NOT AC line frequencies.
Not so. I could show you several switchyards within a short drive that use
many hollow tube conductors all over the yard.
daestrom
| |
| TokaMundo 2005-08-02, 7:21 pm |
| On Tue, 02 Aug 2005 13:48:47 -0500, John Fields
<jfields@austininstruments.com> Gave us:
>BTW, pure water _is_ a dielectric and dissimilar metals in contact
>with each other and pure water would not corrode.\
BTW nearly any metal in contact with "pure water" makes it pure no
more.
| |
| TokaMundo 2005-08-02, 7:21 pm |
| On Tue, 02 Aug 2005 15:03:41 -0500, John Fields
<jfields@austininstruments.com> Gave us:
>On Tue, 02 Aug 2005 17:31:30 GMT, TokaMundo
><TokaMundo@weedizgood.org> wrote:
>
>
>---
>Back looking for some more lumps, bonehead? OK, I'm happy to
>oblige...
>
You're an idiot.
>First, it's called "galvanic corrosion"
Wrong. The result is corrosion. The activity is called "reaction".
Your favorite web site which you posted a reference to speaks about
the end result.
The moniker I gave speaks about the process itself.
You're a fucking jackass. Everybody speaks about that.
> and, second, if you knew
>anything about it and had somehow managed to pull your head out of
>your XXX
Two more reasons you should be on everyone's filtered list.
> before commenting,
I commented on how much of an XXXXXXX you are. When I say
something, you come back demanding proofs, yet you get to make a
jackjawed remark like "not true" and think you won't see anything said
about how much of an XXX you are? Sorry, CHUMP! You don't get that.
> you might have noticed that the poster
>made no mention of the electrolyte required for the corrosion to
>occur.
Oh boy!
> That's why what he said wasn't true.
And THAT is also what you should have said in your post, dumbfuck.
| |
| TokaMundo 2005-08-02, 7:21 pm |
| On Tue, 02 Aug 2005 15:20:32 -0500, John Fields
<jfields@austininstruments.com> Gave us:
>Yup; wrong is wrong.
And that be you. Your method is wrong, and wrong is wrong.
You're fucked John. No way out.
| |
| daestrom 2005-08-02, 7:21 pm |
|
"Dimitrios Tzortzakakis" <dimtzort@otenet.gr> wrote in message
news:dcnpft$3pu$1@usenet.otenet.gr...
>
<snip>
> give
> not
> Yes, but also in voltages >=15 kV there's a signifigant skin effect,
> that's
> why all transmission conductors are constructed with a steel *core* and an
> *aluminium* outer sheath, because the current tends to flow on the skin of
> the conductor.I mentioned corona discharge, to bring into evidence the
> very
> strong electric field around the conductor in very high voltages.
Nonsense. High voltage DC has about the same corona problems as high
voltage AC. The amount of corona discharge is a function of the electric
field gradient and has nothing to do with skin effect. Like I said before,
you've mixed up two different phenomenon that are completely unrelated.
ACRS cables have steel wires, but they are not all bundled in the center.
They are distributed in a circle about 1/3 of the way out from the center.
Dead center is Al strands, as well as the outer periphery. The reason for
the steel is *not* skin effect, nor have anything to do with corona
discharge. It is strength reinforcement, pure and simple. Nothing more.
The elasticity of an all AL conductor would cause too much 'stretch' in the
conductor, and too much rise/fall with temperature change.
daestrom
| |
| daestrom 2005-08-02, 7:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:atnte1h4fuokfj67a2eu9ck8mtmnoj2osj@4ax.com...
> On Tue, 02 Aug 2005 00:45:43 GMT, "daestrom"
> <daestrom@NO_SPAM_HEREtwcny.rr.com> Gave us:
>
>
> For AC at this frequency there is nil skin effect.
>
That depends on one's definition of 'nil' I guess.
> Current in a wire will heat the wire evenly if it is of one
> material.
Not quite. If by 'heat the wire evenly', you mean heat is generated equally
in each unit of cross-section, yes. Since the resistivity of the material
is a constant, and if the current density is uniform throughout, then the
amount of I^2R losses in each unit cross-section is the same. But the
material in the center will be a higher *temperature* than that around the
periphery. It's simple really, the heat generated in the center must be
conducted to the circle of material surrounding it. The heat from the
center, combined with the heat generated in the circle of material must now
be conducted to the next circle of material surrounding that. And so on...
So the material just under the surface has heat generated directly in it,
*PLUS* all the heat generated in interior material conducted into it. For
uniform heat generation throughout the material, it is simple integration to
show that the temperature profile is a parabolic with the apex at the
centerline and temperature falling off as one moves further from the center
to the outer surface.
So the *temperature* profile throughout the conductor is far from 'even'.
If the material has a positive temperature coefficient of resistivity (as do
both copper and Al), then the resistence of the central core is higher than
the outer surface. The exact amount of temperature difference is a function
of the electrical resistivity and thermal conductance of the material.
daestrom
| |
| daestrom 2005-08-02, 7:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:mhbve1p34rfo2cpma8te55gjbgclte2a0j@4ax.com...
> On Tue, 02 Aug 2005 04:41:38 -0500, John Fields
> <jfields@austininstruments.com> Gave us:
>
>
> It's called galvanic reaction.
>
> The Navy seems to think it's real. Does that make you an idiot?
The Navy knows it's a problem, but then naval ships are in seawater. One
must have an electrolyte to complete the 'circuit'. This is one reason why
commercial work with Al conductors often requires the application of special
'grease' to seal the connection from moisture intrusion.
daestrom
| |
| Bob Myers 2005-08-02, 8:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:jafve1hre6689flur22a1l4nq22ecdjvp6@4ax.com...
>
> No. What the figure tells one is where the current is near zero,
Not at all. You're apparently using a very interesting, albeit
incorrect, definition of "skin depth." As has already been pointed
out numerous times, the "skin depth" figure that results from the
calculations you've been using is where the current density is
down to about 37% of its "surface" value (not 37% of the conductance
or loss or any other nonsensical notion that you seemed to think
in a previous post). There is clearly still current farther from
the surface than the "skin depth," and it is also clear that the
density above that value is non-uniform. This IS important,
and again I would suggest you check the values through an
actual loss calculation to see just how big the effect can be.
>
> Try being less stupid. THAT is what is unwarranted here. Unless,
> of course, it just comes naturally for you.
That comment is particularly ironic, along with:
> More stupidity. That was merely one location that I pointed out.
> It explains it quite well, however, and much better than your
> insulting XXX does.
given the following:
> You might get along with folks, if you stop with the bullshit
> insults. Sorry if YOU don't see your remarks that way, but I know
> better. Both about the remarks, and the topic.
Talk about the pot complaining about the complexion of the
kettle...
Further nonsense:
>
> Pure aluminum or pure copper runs will see no difference.
Translation: you didn't bother to run the numbers, or you wouldn't
be saying something so obviously incorrect. Next time, show your
work.
Bob M.
| |
| Bob Myers 2005-08-02, 8:21 pm |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:7nfve1h2bpjcq2eod5p0jbg4v279gkab90@4ax.com...
>
> Look up Galvanic reaction in ship hulls, and you will find that all
> Navy ships have provisions to reduce it.
But that wasn't the question. You were responding to a comment made
in the specific context of gold-on-copper, to the effect that "galvanic
reaction" was the reason that such a combination wasn't a good idea.
Sorry, but the "galvanic reaction" of dissimilar metals has absolutely
nothing to do with the subject at hand.
There actually very often IS another layer (commonly, nickel) placed
between a copper conductor and a top protective layer of gold, but
this has nothing whatsoever to do with a "galvanic reaction" between
these two metals. (If it did, following the original incorrect response
on this subject, the problem would then become WORSE due to the
fact that there would now be two such interfaces rather than one.
Remember, if you can, that the original comment along these lines said
that a "galvanic reaction" was a problem between ANY two metals.)
The reason that an intermediate layer of nickel is often used in this
case has to do with the fact that, left to themselves, gold and copper
will tend to diffuse into one another. This causes a problem in
electrical applications (where gold-plating copper conductors is being
done to prevent corrosion) primarily on the gold side of things, as
the copper diffusing up through the gold layer will eventually reach
the surface and create the very same corrosion problem that the gold
was supposed to be preventing. Nickel doesn't diffuse into gold
like copper does, hence its use here.
> Note again that my reference is to the effect, not the remarks about
> specific elements. Learn to read.
My, again with the personal attacks; I suppose in the absence of
practical knowledge, that's about all one is left with.
Bob M.
| |
| John Fields 2005-08-02, 8:21 pm |
| On Tue, 02 Aug 2005 21:46:40 GMT, TokaMundo
<TokaMundo@weedizgood.org> wrote:
>On Tue, 02 Aug 2005 15:03:41 -0500, John Fields
><jfields@austininstruments.com> Gave us:
>
>
> You're an idiot.
>
>
> Wrong. The result is corrosion. The activity is called "reaction".
>
> Your favorite web site which you posted a reference to speaks about
>the end result.
---
Right. That's what the topic is about : galvanic corrosion, and
which is what all of us, except you, have been talking about.
---
> The | | |