Motor T-Lead Lugs to Power Cable Lugs

[ee13eng]

I need to choose lugs for connecting a 4160 V motor to its power cables. Currently the motor t-leads are tin-plated and the power cables going to the motor have silver-plated lugs. Is there any reason why you would choose tin over silver or vice versa? Is one metal more corrosion resistant? Would there be any problem connecting different type metals together in this application?

 

[7anoter4]

"The tin-to-gold and tin-to-palladium system are judged slightly worse,
and tin-to-silver combination,slightly better than tin-to-tin"
See:

http://www.te.com/documentation/whitepapers/pdf/p316-90.pdf

I purchased silver-plated lugs from Thomas & Betts for cable in contact with motor tin-plated terminals and no complaint was recorded.

 

[ScottyUK]

Silver really doesn't like hydrogen sulphide so for a motor in an enviornment where H₂S is present, such as a wastewater plant or a refinery, you would avoid silver like you would avoid anthrax.

 

[davidbeach]

avoid silver like you would avoid anthrax.

What, and miss all the excitement? ;-)

 

[7anoter4]

There is a lot of pro and cons about silver plated contact. See for instance:

http://www.tecc.com.tw/image/EN_Electric Contacts and switches.pdf

ch.2.4 Good corrosion resistance.
"Even sulfide or oxidation layers was formed, it will sublimate due to heat generated instead of forming an insulating film"

 

[electricpete]

I am under the vague impression that silver plated copper is more of a standard and perhaps more reliable (excluding special chemical environments).

I'm not sure where that idea came from... it's just the way I've always seen it done (silver plated).

Do people commonly use tin plated copper lugs on large power equipment ?

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[electricpete]

I did find this brief discussion (just for info)

http://www.usbr.gov/power/data/fist/fist3_3/vol3-3.pdf?wwparam=1367239090

3.6. PLATING OF CONDUCTORS.- Silver oxide is easily broken down by contact pressure and forms less readily at elevated temperatures. Therefore, silver plating is recommended for copper contact surfaces which must be operated at elevated temperatures. in and nickel platings are sometimes used on copper and aluminum connectors to prevent the formation of oxides. However, when wet, these plated metals can cause galvanic corrosion.

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[jraef]

The athoritative treatise on "silver whisker" formation. Be forewarned, there are some scary pictures here.

http://nepp.nasa.gov/WHISKER/other_whisker/silver/

"Will work for (the memory of) salami"

 

[electricpete]

You can't mention silver whisker without mentioning tin whisker:

http://nepp.nasa.gov/whisker/background/

http://nepp.nasa.gov/whisker/background/index.htm#q6

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[electricpete]

Tin whiskers pose a serious reliability risk to electronic assemblies.

That is the main concern for metal whiskers to my understanding... electronics, not power equipment.

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[electricpete]

not power equipment

Not lugs and bolted connections, anyway.

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