|
Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
|
|
|
Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
|
In Reply to: The explanationsI read were slightly different posted by Soundmind on July 9, 2006 at 11:24:50:
eventually, plastic deformation of the wire would cause it to no longer offer resistance to the screw, it would loosen .../...This plastic deformation is what I meant when I wrote "are prone to breaking or to flowing aside. The cause of this deformation is ultimately the metal hardening thanks to a change in its crystalline structure. Anyway the result is the same. BTW, if you have the occasion of holding in your hands a piece of old aluminum wire, you will note how stiff the wire became (often too stiff for the insulator of the time which is often brittle and no more supple -another hazard- ), and after one or two bends, you'll break it apart.and the resulting arcing would cause oxidation, more arcing and eventually a fire.Arcing is the final stage only, just when fire ignites. The reason is that you need at least 70V to initiate any arcing. As long as the contact still exists somewhere, the voltage will stay too low to intiate arcing.
A numerical example: have a wire carrying 100A, and the contact is hundred times 10 milliohms in parallel (for example 100 threads in the wire).
When new, the power loss is RxI2 which gives exactly 1 watt, so hardly warm.
Years later, only 10 contacts remain, the power loss is 10W, really hot in a small box. Voltage is only 100mV, so, still no arcing.
With less than 10 contacts left, fire hazard is obvious.
Suppose only one contact is left, power dissipation is 100W, fire ignites in any small box. Voltage is still only 1 volt. No arcing.
Only once temperature goes so high as to melt aluminum and retract the wire is arcing to occur between melted metal wetted parts.
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- No arcing until the final fire! - Jacques 12:27:09 07/09/06 (5)
- Re: No arcing until the final fire! - chris_w 02:38:45 07/16/06 (3)
- This is much closer to my experience, arcing can continue for a considerable time nt - Soundmind 18:05:45 07/18/06 (0)
- Yep - Ted Smith 10:03:16 07/16/06 (1)
- Re: Yep - Soundmind 18:22:51 07/18/06 (0)
- you will find a similar problem with underfloor "flatwire" in open landscape offices - Soundmind 13:57:25 07/09/06 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
