[R-390] Wire problems in mechanical filter coils and transformers

[Tim Shoppa]

Sheldon wrote:
> Test and Measurement World magazine of May, 2007, has a
> multiple page article on "Wire Ends Yield Failure Clues,"
> discussing a variety of factors that can cause
> "magnet" wries to break, causing devices such as
> transformers and inductors to suffer
> catastrophic failures.
> This should go to the web version of the story:
> http://www.tmworld.com/article/CA6436546.html 

Thanks Sheldon!

I would guess that by the article's categorization:

* Coils that fail where the wire goes onto a terminal are
   "Tensile Failures".

* Coils that fail due to an open in the middle of a coil
   might be "fusing" failures (overcurrent, due to a
   shorted or just plain leaky coupling capacitor).
   42 gauge wire has a fusing current of more than
   an amp(!!!!!) but if an amp flowed through the
   approx 100 ohm coil, it'd be dissipating 100 watts,
   and obviously the wire would open in the coil
   itself rather than near the terminal (which would
   actually work as a heat sink).

I also have failed mechanical filters with shorts between
the coil and the can, and also with excessive leakage
between the coil and the can.

Tim.