I have read of others using steel in a similar application, and they had problems with the rod plastically deforming due to the resistive heating and gravity, which is what I'm trying to avoid. I think maybe a ceramic(regular cement perhaps) coated with a suitable conductor might be the only good solution. Fortunately the rod should be easily replaceable. Unfortunately other considerations make it desirable that this rod be as thin as possible.

I take it all of the tungsten alloys for contacts are made using powder metallurgy as well. Do you know if there are any obstacles to producing longer lengths, other than the low demand, with powder metallugy? I have a bicycle with a frame made a steel/boron composite and I have seen Ti-SiC in some aerospace applications, both of which at least as long as I need. I fear the way they work might be closer to carbon and iron in steel.

If I am unable to eliminate arcing I'll just have to use it to my advantage which will require good arc resistance.

Thanks for your help,

Ben

--Previous Message--
: --Previous Message--
: I need to conduct several tens to hundreds of kA though a thin sliding
: contact rod. I've yet to settle on a size because it will partly depend on
: the material. I don't like copper for fear it will begin to melt.
: It needs to be arc resistant, high melting point, and good conductivity.
: I would use elkonite (the WC Ag variety) but it doesn't come longer than
: 12" apparently. The other option I've come up with is Cu Zr but I've
: done little reasearch on this yet.
: What are other good materials for this application? they need to come in
: >3 ft lengths.
:
: Hello Ben,
: Is the intended application DC, low frequency AC, or a pulsed application?
: Also, what material(s) are you planning to use to make sliding contact to
: the rods? Finding the proper material combination will be critical since,
: at high current densities, contacts become unstable due to the interactions
: between magnetic repulsion forces and current constriction at the
: individual points of contact. This can leading to arcing and rapid
: deterioration of the contact area. The challenges of making high current
: sliding contacts have been worked by developers of high current homopolar
: generators or compulsators. Copper-graphite (fabricated via powder
: metallurgy) seems to be the material of choice for high current brushes.
: The potential rod materials you've researched are reasonable choices for
: high current contact applications. As you've found, they are all fabricated
: using powder metallurgy and they are not generally available in lengths
: greater than 8-12". There's also an inverse relationship between the
: electrical conductivity and wear resistance, and the effective melting
: temperature of the rod may still be limited to that of silver.
: If your application is mainly DC or long pulse duty, I'd consider using
: electrolytic silver square or hexagonal bar stock to provide the lowest
: resistance conductor. You could then silver solder or braze shorter lengths
: of thin WAg or WCAg rectangular bar stock to the flat outside surfaces of
: the silver rod to form tough, arc-resistant contact strips. The resulting
: composite structure should provide an optimal combination of wear
: resistance and low electrical resistance.
: Good luck and best regards,
: -- Bert --
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