Termination of an ultra low resistance circuit

[alansimpson]

I need to make up an ultra low resistance circuit in a loop (below 40 micro ohms) with multi-stranded copper wire like Litz wire.

I estimate total circuit length needs to be a around 400 mm. Based on this the litz wire needs to be a large cross sectional area.

My major concern is the termination at the ends of wire would increase the overall resistance of the circuit. Soldering seems to be the most obvious but I am not sure how to calculate the resistance of the soldered joint. Also how reliably can I make a soldered joint at a termination of 1000s of small copper wires. Thankfully the termination does not have to be multi stranded. In fact the multi stranded parts of circuit only needs to be two short sections. The remainder could be solid copper. However this would increase necessary terminations to four instead of one.

This is not the usual application of litz wire.

Is soldering the best method and how should I go about soldering a large bundle of wires? How could I estimate resistance of termination?

Any suggestions welcome.

Thanks

 

[MikeHalloran]

A fellow I knew used to make really nice copper bracelets out of the heavy braided fine stranded copper cable used in spot welders. Not quite Litz wire, but certainly enough surface area to make soldering tricky. He didn't solder it; the ends were fusion welded, I'm guessing with a TIG welder.

I'd think the hard part is cleaning the insulation from the individual conductors of the Litz wire.



Mike Halloran
Pembroke Pines, FL, USA

 

[ScottyUK]

What about a laminated busbar in lieu of Litz wire? They are basically copper foils interleaved with kapton film, and offer a high-current equivalent to Litz wire. Maybe not quite as good as Litz at very high frequencies but much more practical at medium frequency.


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If we learn from our mistakes I'm getting a great education!

 

[VEBill]

American Superconductor (

http://www.amsc.com)

might be able to help. They're at the point where they do provide real-world practical solutions.

 

[electricpete]

I have never worked with Litz wire, but a question and some thoughts:

What is the normal procedure for terminating Litz wire in any application? I would assume maybe there is some chemical solution that could be used to strip the insulation off a suitable length at the end? Else could try to use something like sandpaper but that seems cumbersome and error prone if there are large numbers of strands.

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[Skogsgurra]

For radio applications, we used to (yes, I AM old) use alcohol in a little cup. Set it afire and dip the wire multiple times. The alcohol and the heat took care of the insulation. Don't know how that would work for heavy litz, though.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Comcokid]

I investigated how litz wire would be tinned for termination a year ago. As I recall, there are several methods depending upon the insulation type. The various methods involved alcohol flame, or bunsen burner, or a solder pot, and liquid flux. However, I never attempted it.