Hi Resitance Short

[hotspot]

Anyone want to give a shot at explaining a common thermographic term in equation form? The term "hi-Resistance-Short" is used to describe a localized hot spot on electrical contacts/connections. Trying to explain this term litterally as a function of common electrical laws seems rough, or I missed a point. Any help appreciated.

 

[IRstuff]

If it were a low-resistance shunt path, you wouldn't be able to see it in the IR, since it wouldn't dissipate much power. Only a higher-resistance shunt path would dissipate sufficient power to cause an infrared signature.

TTFN

 

[electricpete]

"hi-resistance short" is not a common term to my knowledge.

We often have high resistance connections which show up as hot spots.


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[maged541946]

That happens when contacts either get oxides as a result of arcing during make/break actions or wear out, the contact will have higher resistanse due to contact area reduction due to non uniformitty of contact surface or oxide on contacts, as the same current must flow in them (normally controlled by load conditions and voltage source, the generated heat in them will increase as a result of equation:

Power(heat)= I*I*R (sorry I can't write squared symbol)

Now R is increased so Heat is increased causing more heat and oxidization and more increase in R and so on in this regenerative action.

Maged A. Mohamed

http://magedm.freeyellow.com

http://www.magedsoft.com

 

[hotspot]

Thanks Majed,

It looks like I looked too deep. The answer is not with Ohm's Law but in the power equation and perspective. The hot spot(high resistance short)is an unintentional load on the current loop that affects resistance and source current and therefor power measured at the source. Thanks to all for your response.

 

[maged541946]

Thanks to you too

Maged A. Mohamed

http://magedm.freeyellow.com

http://www.magedsoft.com