Electronics > Mechanical & Automation Engineering

copper braid/screen/shield dipped in solder bolted on star earth ground?

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coppercone2:
So this miller has a big star earth ground, and they use 1 brass stud inside of aluminum bracket to connect a whole bunch of grounds.

They have 4 ring terminals and 3 pieces of solder braid dipped in solder on one screw.

I am thinking that solder braid/copper screen dipped in solder is not a good thing to put on the main earth ground?? I was thinking I should solder a strip of copper to that, so that there is no solder in the bolt tension.

Surprised to see that from miller in a high end welder.. Is it for some reason acceptable to do this?

Benta:
I'm not sure what a "miller" is. Do you mean a mill, like for metal cutting/milling?
Anyway, putting tin-based solder under mechanical stress is never a good idea. This includes pressure.
Tin solder cold flows, meaning it will deform over time and lose the connection. This is dangerous from an electrical point of view, but also a fire hazard.
The same thing happens for aluminium, by the way, with the added fire hazard of oxidization. This makes me a bit concerned about your "aluminium bracket".

The correct way is using crimped ring- or fork terminals for the bolt.

coppercone2:
miller electric dynasty 200 welding machine

The machine is built like I beam in a box, with bracket in middle that PCB and IGBT go on both sides. The front ground for several PCB is a brass stud embedded in this bracket, which has 7 connections consisting of 3 braids and 4 ring crimps.

it was considered a world class TIG welding machine

I thought maybe they used braze, but I see there is rosin flux residue on the braid, meaning it is in fact soldered. :-\

Ian.M:
Yeah, that's *NOT* *GOOD* and possibly illegal for a safety ground as solder-tinned stranded wire will cold flow and deform under clamping pressure, resulting in a bad connection, as Benta has already mentioned.   It could be converted to solderable ring terminals for functional grounding but if any of those braids is a safety ground, all solder-contaminated braid must be cut back and crimp ring terminals properly fitted.

bill_c:
Does it show any signs of poor connection or burnt areas?  I'm sure they tested it during the design phase, but there is also a possibility it was designed that way to fail out of warranty.

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