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Skin Effect in Solid/Stranded/Litzendraht Wire -Guy Macon

E

Ecnerwal

Jan 1, 1970
0
Guy Macon said:
....
I am curious about the four cables. Three phase is usually
configured as delta (no neutral), not wye at those voltage
and power levels. HVDC tends to use two condutors, and even
the fairly rare six phase and twelve phase systems don't use
four conductors. Any idea what was going on there?

Perhaps each of the 3 sets included one spare conductor? Between "cost
of digging trench" and "Cost of being down" a high degree of redundancy
might well make sense .vs. saving money on cables at installation time.
 
R

Robert Baer

Jan 1, 1970
0
Tom said:
Thanks, JK^2! That leads to some explanations about the methods used
to keep galvanic action from wiping out the steel core in short
order. I know from experience that a small nick in a copper-clad
steel conductor will cause the steel to corrode quickly (and generally
the wire breaks then). Interestingly, a search on "CCSR" yielded
nothing interesting, and on "copper conductor steel reinforced" seems
to just yield pointers back to copper conductors or steel reinforced
aluminum conductors. Thanks again for the search term that let me
actually learn something. (Now we'll see what the local power company
replies to my question about the conductors they use for both long-
distance and local distribution...)

Cheers,
Tom
Recently, an article in EE Times (Oct 8, p.39) about protecting
electrical devices has some nice data on skin depth.
They explain it is due to "..a back EMF is created in the center of
the conductor, which opposes the current flow".
Hmmm...i thought that the current flow created a magnetic field (in
this case cylindrical, centered at wire center) and the "inner" field
opposed the "outer field", thereby "pushing" the current away from the
center.
So..one could correctly say that there is a "skin effect" even at DC.
One could observe this at reasonable currents (say 100 amps) using
multiple wires (thin insulation if one wishes) twisted around a central
wire.
 
J

JosephKK

Jan 1, 1970
0
Tom Bruhns [email protected] posted to sci.electronics.design:
Hi Win,

Ah, back when copper was cheap... ;-)

Of course, that's an entirely different application than the one I
was thinking of, where the wire is strung between towers and
generally is
not insulated -- and where strength matters. Tim W. says that yes,
cores are commonly steel. I tried a web search just now but didn't
turn up anything useful. Maybe I'll drop a note to our local PUD or
the like and see what they say. I suppose with the current price of
copper, Pirelli would consider making the core from some relatively
inexpensive and much lighter material. I wonder if the construction
of long distance transmission lines was covered in that old power
engineering book you got from me about three years ago. Might be
interesting to compare "then" and "now."

Cheers,
Tom

Try "ACSR" (aluminum conductor, steel reinforced). There is a whole
series of standard sizes named after birds.
 
T

Tom Bruhns

Jan 1, 1970
0
Tom Bruhns [email protected] posted to sci.electronics.design:








Try "ACSR" (aluminum conductor, steel reinforced). There is a whole
series of standard sizes named after birds.

Thanks, JK^2! That leads to some explanations about the methods used
to keep galvanic action from wiping out the steel core in short
order. I know from experience that a small nick in a copper-clad
steel conductor will cause the steel to corrode quickly (and generally
the wire breaks then). Interestingly, a search on "CCSR" yielded
nothing interesting, and on "copper conductor steel reinforced" seems
to just yield pointers back to copper conductors or steel reinforced
aluminum conductors. Thanks again for the search term that let me
actually learn something. (Now we'll see what the local power company
replies to my question about the conductors they use for both long-
distance and local distribution...)

Cheers,
Tom
 
J

JosephKK

Jan 1, 1970
0
Tom Bruhns [email protected] posted to sci.electronics.design:
Thanks, JK^2! That leads to some explanations about the methods
used to keep galvanic action from wiping out the steel core in short
order. I know from experience that a small nick in a copper-clad
steel conductor will cause the steel to corrode quickly (and
generally
the wire breaks then). Interestingly, a search on "CCSR" yielded
nothing interesting, and on "copper conductor steel reinforced"
seems to just yield pointers back to copper conductors or steel
reinforced
aluminum conductors. Thanks again for the search term that let me
actually learn something. (Now we'll see what the local power
company replies to my question about the conductors they use for
both long- distance and local distribution...)

Cheers,
Tom

You are welcome.
 
R

Rich Grise

Jan 1, 1970
0
Recently, an article in EE Times (Oct 8, p.39) about protecting
electrical devices has some nice data on skin depth.
They explain it is due to "..a back EMF is created in the center of
the conductor, which opposes the current flow".
Hmmm...i thought that the current flow created a magnetic field (in
this case cylindrical, centered at wire center) and the "inner" field
opposed the "outer field", thereby "pushing" the current away from the
center.

Yes - that's two different ways of saying the exact same thing.
So..one could correctly say that there is a "skin effect" even at DC.

Probably not - a DC magnetic field doesn't generate any back EMF.
One could observe this at reasonable currents (say 100 amps) using
multiple wires (thin insulation if one wishes) twisted around a central
wire.

OK, go ahead and do the measurements, and post your results.

Thanks!
Rich
 
S

Spurious Response

Jan 1, 1970
0
Probably not - a DC magnetic field doesn't generate any back EMF.


Bullshit. It does upon energization, and upon removal of power. That
is, in fact, EXACTLY how a car coil works.
 
T

Tim Williams

Jan 1, 1970
0
Spurious Response said:
Bullshit. It does upon energization, and upon removal of power. That
is, in fact, EXACTLY how a car coil works.

LOL. So the only back EMF from a "DC" field is when it's no longer DC, eh?

Point in case.

As punishment, do ten Fourier transform integrals.

Tim
 
J

JosephKK

Jan 1, 1970
0
Spurious Response [email protected] posted to
sci.electronics.design:
Bullshit. It does upon energization, and upon removal of power.
That
is, in fact, EXACTLY how a car coil works.

Wrong again. It is a simple flyback converter.
 
G

Guy Macon

Jan 1, 1970
0
Tim said:
Spurious Response wrote...


LOL. So the only back EMF from a "DC" field is when it's no longer DC, eh?

Point in case.

As punishment, do ten Fourier transform integrals.

Unless the voltage has existed since before the beginning of time,
it isn't really DC -- just a reeeaaallly low frequency AC. <grin>

that's what makes doing those ten Fourier transform integrals so
tough; the infinity that pops up when you try to calculate zero
frequency <bigger grin>.
 
R

Robert Baer

Jan 1, 1970
0
ChairmanOfTheBored said:
In current solid state designs, yes. Capacitive discharge even (a DC
pulse).

In the days of points, absolutely not.
The Kettering spark system is a classic Flyback circuit.
 
R

Robert Baer

Jan 1, 1970
0
ChairmanOfTheBored said:
**** you, you fucking idiot. Hey, asswipe... over here, we CAPITALIZE
the word I, you uneducable fucktard!




I do not have to compare anything, and I do understand. I built HV
power supplies for the last ten years, asswipe.

A TV deflection circuit is NOT a flyback supply, idiot. The flyback in
a TV is in the ANODE supply, you stupid ****.
-------------^^^^^
So??
It *is a flyback system, and labelled as such in a lot of Sam's
FotoFax (to be punny).
 
C

ChairmanOfTheBored

Jan 1, 1970
0
LOL. So the only back EMF from a "DC" field is when it's no longer DC, eh?

Point in case.

As punishment, do ten Fourier transform integrals.

Tim


No, idiot! It IS DC! It is a standing field the entire time the
points are closed. The moment they open, the field collapses, and that
is where your precious back EMF resides.
 
C

ChairmanOfTheBored

Jan 1, 1970
0
Spurious Response [email protected] posted to
sci.electronics.design:


Wrong again. It is a simple flyback converter.


In current solid state designs, yes. Capacitive discharge even (a DC
pulse).

In the days of points, absolutely not.
 
C

ChairmanOfTheBored

Jan 1, 1970
0
Unless the voltage has existed since before the beginning of time,
it isn't really DC -- just a reeeaaallly low frequency AC. <grin>

that's what makes doing those ten Fourier transform integrals so
tough; the infinity that pops up when you try to calculate zero
frequency <bigger grin>.


That's what certain maths are all about. NEAR infinity, and NEAR zero
work causes some strange and important figures to arise.

One is:

Betty Boop :-]

Put that in your pipe and smoke it.
 
J

JosephKK

Jan 1, 1970
0
ChairmanOfTheBored [email protected] posted to
sci.electronics.design:
In current solid state designs, yes. Capacitive discharge even (a
DC
pulse).

In the days of points, absolutely not.

If you were educable i could bother, but that is not the case. If you
compared the various waveforms of TV deflection circuits and compared
then to automotive ignition you could understand. But you won't so
you don't. Not my problem, yours and only yours.
 
C

ChairmanOfTheBored

Jan 1, 1970
0
If you were educable i could bother, but that is not the case.


**** you, you fucking idiot. Hey, asswipe... over here, we CAPITALIZE
the word I, you uneducable fucktard!
If you
compared the various waveforms of TV deflection circuits and compared
then to automotive ignition you could understand.

I do not have to compare anything, and I do understand. I built HV
power supplies for the last ten years, asswipe.

A TV deflection circuit is NOT a flyback supply, idiot. The flyback in
a TV is in the ANODE supply, you stupid ****.
But you won't so
you don't.

You're a goddamned idiot. Nice assumption there, you fucking retard.
That's like me saying "since you assume, you MUST be retarded." Guess
what, dipshit? My remark is far closer to being correct than your is or
ever could be.
Not my problem, yours and only yours.

IF you even knew what a collapsing magnetic field does, you MIGHT
understand. The problem is 100% yours, idiot.
 
W

Winfield

Jan 1, 1970
0
ChairmanOfTheBored said:
They were very likely DC links.

No, it was 60Hz ac, 115kV. I know because they asked
us if we'd be affected by the radiated magnetic field,
being only 100-feet away from our labs, and they and we
undertook an analysis, which showed we were OK about it.
(I had suggested they twist the "wires" but that didn't
go over well, they didn't want to twist four conduits.)
 
C

ChairmanOfTheBored

Jan 1, 1970
0
No, it was 60Hz ac, 115kV. I know because they asked
us if we'd be affected by the radiated magnetic field,
being only 100-feet away from our labs, and they and we
undertook an analysis, which showed we were OK about it.
(I had suggested they twist the "wires" but that didn't
go over well, they didn't want to twist four conduits.)


If they were in heavy lead jackets, it is very likely that there would
have been no radiated EMI even a few feet away.

More like twisted brains.
 
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