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Alu Cables for Aeroplanes

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Enthalpy:
Hello nice people!

High voltage lines use aluminium wires: lighter and cheaper than copper at identical resistance. Homes don't because bad contacts created accidents. Even aeroplanes don't, seemingly for that same reason.

But as aeroplanes care about mass and their future is hybrid or electric, with Zn-air batteries or liquid hydrogen and fuel cells, they strongly need aluminium wires, and have the means to develop good contacts.

Bad contacts shall possibly result from more conductive but creeping alloys like AA1350. The cable's end squeezes over time, the contact pressure vanishes, the contact gets bad.

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Plane designers could first check if the solutions for high voltage lines fit planes.

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I suggested already to solder Ag-coated Al cables in Cu-alloy clips.
  scienceforums
Sn-Pb solder is reliable, Sn-Pb-Ag is more caring with the Ag layer. But this builds corrosion couples usually forbidden in plane design. So here are proposals using Al-alloy cable ends, of corrosion-safe alloys like AA5083, AA5457, AA6062, AA3004 and few more.

Electric planes will transmit >2×30MW. Friction stir welding, FSW can join the massive AA1350 bars on AA5083 ends
  wikipedia
I trust the resulting alloy gradient. Would the method even keep cold-work hardening, welcome at the contact?

Welding is to slow for smaller cables. If soldering, corrosion lets me prefer an Al-base filler. The usual eutectic AlSi13 filler melts at 580°C, excluding parts of much-alloyed Al, especially AA5083 that melts at 580-640°C. Melting at 450°C, the less usual AlMg38 eutectic might solder AA1350 cables in AA5083 ends. And could a heat sink protect the cold-work hardening at the tip that makes the mechanical contact?

Marc Schaefer, aka Enthalpy

Hunter2:

--- Quote ---High voltage lines use aluminium wires: lighter and cheaper than copper at identical resistance.

--- End quote ---
No copper has lower resistance as aluminium.

https://instrumentationtools.com/wp-content/uploads/2020/03/Specific-resistance-table.png

The Alloys of aluminium have more higher resistance, so they will be not used. For signal Iines glasfibre should be considered, for higher voltage still copper or coated aluminium with copper should be used.

Enthalpy:
Harder but corrosion-safe alloys (AA6101, AA6063, AA6060, AA5083, AA5754 and more) are easily welded with high-conductivity aluminium, so many processes can join harder tips with massive bars.

Friction welding is fast and simple on round conductors, feasible on other sections too.
  wikipedia - wikipedia
Or just TIG and MIG, which accept many sections and can be automated.

Enthalpy:

--- Quote from: Hunter2 on March 13, 2023, 06:38:45 AM ---[...] copper has lower resistance than aluminium[...]
--- End quote ---

Hi Hunter2, nice to read you!

At identical dimensions, copper has a lower resistivity.

But we can increase the section of an aluminium bar to have the same resistance, and thanks to its much lower density, the aluminium bar is much lighter than the equivalent copper.

This is useful at high voltage lines, and even more at aeroplanes.

billnotgatez:
@Enthalpy
In my youth I worked on helicopter electrical systems.
I have no memory of aluminum wires being used.
Have things changed that much?
So you have examples of published specs?
I do remember Chromel and alumel are used for turbine EGT thermocouples

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