"Semiconductor" sheath on cable?

[Bob Masta]

Greetings:

A friend is an electrician who works
mainly on intallations at factories, etc.
He has a beverage coaster made from a
thin cross-section of a "primary" cable,
the kind that brings power into the plant.
It has a central conductor area of many
strands of heavy-gage wire, then an
insulating sheath of something rubbery
that looks sorta like that red HV silicone
rubber, then a very thin metallic layer
which he called a "semiconductor shield"
before the final insulating jacket.

I tried to find out exactly what he meant
by "semiconductor" in this context because
I couldn't picture silicon or germanium, for
example, being made into a flexible foil.
(Well, maybe not *too* flexible, since the
cable was several inches across!) He said
he really didn't know about such things,
but that the layer was supposed to reduce
the magnetic fields from around the cable,
which otherwise were a problem at the
high voltages and currents involved. (Which
he also didn't know the levels of.)

Anyone familiar with this technology?

Thanks!


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

 

[Michael Black]

Bob Masta (NoSpam@daqarta.com) writes:

Greetings:

A friend is an electrician who works
mainly on intallations at factories, etc.
He has a beverage coaster made from a
thin cross-section of a "primary" cable,
the kind that brings power into the plant.
It has a central conductor area of many
strands of heavy-gage wire, then an
insulating sheath of something rubbery
that looks sorta like that red HV silicone
rubber, then a very thin metallic layer
which he called a "semiconductor shield"
before the final insulating jacket.

I tried to find out exactly what he meant
by "semiconductor" in this context because
I couldn't picture silicon or germanium, for
example, being made into a flexible foil.
(Well, maybe not *too* flexible, since the
cable was several inches across!) He said
he really didn't know about such things,
but that the layer was supposed to reduce
the magnetic fields from around the cable,
which otherwise were a problem at the
high voltages and currents involved. (Which
he also didn't know the levels of.)

Anyone familiar with this technology?

Thanks!

No, but I think he means "partially conducting" rather than

semiconductor as in solid state devices.

Decades ago, I was given a bit of that stuff, I think it
was left over from a TV transmitter installation. It did indeed
have some conductivity, but not all that much. I played around
with it at the time, because I was interested in electronic music
at the time and there were various controllers based on that sort of
thing. But memory says I didn't find that there was a good relationship
between length and resistance. It just seemed to have some conductivity,
period.

The thing I had was rubber, and it most definitely came from a power
line cable. If I heard a reason for its purpose at the time, I've
long forgotten.

Michael

 

[Rich Grise]

On Thu, 11 Aug 2005 12:26:02 +0000, Bob Masta wrote:

Greetings:

A friend is an electrician who works
mainly on intallations at factories, etc.
He has a beverage coaster made from a
thin cross-section of a "primary" cable,
the kind that brings power into the plant.
It has a central conductor area of many
strands of heavy-gage wire, then an
insulating sheath of something rubbery
that looks sorta like that red HV silicone
rubber, then a very thin metallic layer
which he called a "semiconductor shield"
before the final insulating jacket.

I tried to find out exactly what he meant
by "semiconductor" in this context because
I couldn't picture silicon or germanium, for
example, being made into a flexible foil.
(Well, maybe not *too* flexible, since the
cable was several inches across!) He said
he really didn't know about such things,
but that the layer was supposed to reduce
the magnetic fields from around the cable,
which otherwise were a problem at the
high voltages and currents involved. (Which
he also didn't know the levels of.)

Anyone familiar with this technology?

From what Michael Black said, it's "partially-conductive" material,
probably a lot like that foam that they used to ship chips in.

I'm guessing that it would "suppress" the magnetic field around
the big conductor by eddy currents/back EMF. And of course, since
it's resistive, it has a Q of squat, so instead of a big magnetic
field around the conductor, you have a hot cable.

Cheers!
Rich