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March 2010

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Subject:
From:
Paul Edwards <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Paul Edwards <[log in to unmask]>
Date:
Wed, 31 Mar 2010 17:32:13 -0700
Content-Type:
text/plain
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text/plain (289 lines)
Tried using similar material but had failures at high current loading during turn on and off...
Anything that is fills the gaps in the wire bundles that is not as conductive as the Cu will force localized high current contact points...
These in turn will force the chemical breakdown of the material between the wires and eventually cause a larger failure...
This would occur as the current pulse vaporizes the material between the strands and jets the plasma out of the crimp..

Paul

Paul Edwards
Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Wednesday, March 31, 2010 4:39 PM
To: [log in to unmask]
Subject: Re: [TN] Failed Ring Terminal

Water (condensation) plus air pollution makes anything except a gas  
tight crimped terninal slowly corrode individual strands.  Then the  
current carrying capability of the wire bundle decreases and the joint  
begins to be resistive and heat.  The heat accelerates the oxidation/ 
corrosion.

Instead of solder, try Nyogel 760G connector grease worked into the  
strands.  Put it also on both sides of the ring as well.  Recommended  
by Molex, used by auto and golf cart industry.  Fantastic stuff - 2oz  
tube will last you a long time.

Bob Landman
H&L Instruments, LLC

Sent from my iPhone

On Mar 31, 2010, at 5:37 PM, Robert Kondner  
<[log in to unmask]> wrote:

> Paul,
>
> I agree. Soldering takes SO much longer and it can make a mess of the
> insulation, looks bad. But, if this terminal had been soldered it  
> would
> still be working.
>
> Though, 40 Years in my Dad's barn is more than I would asks of  
> ANYTHING!
>
> Bob Kondner
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards
> Sent: Wednesday, March 31, 2010 5:24 PM
> To: [log in to unmask]
> Subject: Re: [TN] Failed Ring Terminal
>
> Bob,
>
> A soldered crimp terminal is best for high reliability joints...
>
> The surface of the individual strands of wire that makeup the  
> conductor
> oxidize (and/or corrode) because they are exposed to the environment  
> and
> increase the strand to strand resistance... As the current travels  
> from the
> conductor core to the contact surface area of the crimp connector it
> differentially heats the strands in the conductor until you preferred
> current paths... The Cu then starts to thermal cycle under load and  
> causes
> crystallization and failure of the Cu...
>
> A solid solder joint eliminated this problem because of the soldered  
> Cu
> interfaces are complete involved in the solder joint.
>
> Paul
>
> Paul Edwards
> Surface Art Engineering
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
> Sent: Wednesday, March 31, 2010 12:55 PM
> To: [log in to unmask]
> Subject: [TN] Failed Ring Terminal
>
> Hi,
>
>
>
> Why would a crimped ring terminal fail and over heat?  Can anyone  
> suggest
> failure modes as to why the resistance would increase?
>
>
>
> I would guess a soldered connection would be better?
>
>
>
> See www.kondner.com/files/failedringterm.jpg
>
>
>
> That insulator was yellow at one time it is now brown and the  
> insulation at
> that end of the wire is very brittle. The wire size is #10.
>
>
>
> This ring terminal came from a Furnas Electric motor starter for a  
> 5hp 240V
> AC motor that draws about 28 amps. It was installed back in 1968. It  
> was
> installed in a dingy barn in a silo pit where most of the steel  
> enclosures
> are covered with rust. All kinds of nasty odors as there are plenty  
> of cows
> in the area. It is quite amazing that it went this long, but I  
> wonder why it
> failed.
>
>
>
> The crimp seemed tight but it had obviously over heated. Other such  
> ring
> terminal on the same circuit are fine. The crimps were made in the  
> factory
> and not by some guy with a simple hand tool.
>
>
>
> I ground off the edges which allowed me to open the crimp with  
> minimal wire
> damage. I was surprised that much of the wire looked quite clean.
>
>
>
> I am just curious what folks would suggest.
>
>
>
> Thanks,
>
> Bob Kondner
>
>
>
>
>
>
>
>
>
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