Motor terminal fasteners material

[thinker]

Hopefully, this is a well known issue. We receive from Europe electric motors with copper L-shaped power terminals [for current range (400-900)A]. Motor manufacturer includes in scope of supply brass fasteners (nut, bolt, flat washer, lock washer) for all pre-drilled terminal holes. For US installation we will use appropriate UL listed lugs. The installation contractors question why we use brass fasteners. Can we use steel fasteners, for example, blackened, or special plated steel would be required? Please advise.

 

[jraef]

You would have to ask that question of the termination supplier. Sometimes it is an issue of the thermal expansion rates of the dissimilar metals, but generally this is overcome by the use of things like bellville washers. In motor termination boxes however, it can also be a corrosion issue. If you use steel components they can rust and fuse so that someone in the future may end up having to chisel them off. That may damage the motor terminations, which are difficult to replace. Using bronze bolts means less corrosion (of the kind that can fuse the components as rust can).

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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[thinker]

Thanks Jraef, galvanic corrosion is a reasonable approach. What is confusing, that copper bus bar manufacturer ERICO (for example) recommends to use steel bichromated fasteners (SAE Grade 5)with Beleville washers for copper bar connections.

 

[jraef]

Erico may be referring to a generality regarding busbar connections, the motor mfr may be referring to a reality they are aware of.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376