Electronics > Mechanical & Automation Engineering

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

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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?

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.

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. :-\

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.

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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