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Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
I tried improving all connections on my coil and beefing things up to make everything more robust. I used 1/4" nuts and bolts to connect cables and components, but I am finding that the nuts are overheating while the wires themselves are not. Makes me think that there is some induction heating going on? Would think that with the nut in contact with the cable and the bolt it wouldn't. If it is induction heating I expect there are potential losses too. Have not read about this being a problem before. Anyone experienced this or have any ideas? Thanks.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Do you mean that a bolt and nut that presses two conducting wire shoes together, so you have copper against copper or is the current running through the bolt/nut itself?
You could consider using brass bolts/nuts to lower the resistive losses if you run through the bolt.
If you fear it is induction losses you could use stainless steel bolts/nuts which are much less acceptable to induction heating compared to regular steel bolts/nuts.
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
I have both situations - one where a nut and bolt clamps two blade connectors together, and then where the bolt is the conductor through some acrylic connecting internal leads to external leads. All of them get hot. They are just galvanized steel bolts. Definitely doesn't seem right. Thanks for the suggestions.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I agree with Mads, if you want to pass current through a bolt, it has to be brass.
IGBT bricks are supplied from the factory with ordinary steel bolts for the terminals, but the current isn't supposed to pass directly through them. We also use the bricks at higher frequencies than they were designed for, so maybe we ought to be changing the bolts for brass or stainless ones.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
You can also get copper nuts and bolts. Some are even silver plated.
You should consider 'skin effect', though, use larger bolts for a larger surface area. Also, usung 'bolts' rather than 'set screws' should help reduce resistance at high frequencies.
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
Thanks for the replies guys - it definitely is a problem using steel nuts and bolts! I machined some cylindrical aluminum connectors with set screws and the problem went away. Good lesson, and hopefully others can learn from this too. Thanks again.
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Hot connector nuts
