wrote in message
...
I recently replaced a couple of electrolytics in a flat screen TV for a
customer. The caps were in the power supply and were of course rated for
105 degrees C. So this brought to mind a question. Could this possibly be
an operating temperature? Or is it a storage temperature? Or perhaps it's
an internal temperature? It would seem like it would have to be a very
high frequency component to ever cause an electrolytic to ever approach
anything like this. Could one of these parts rated as such actually get
this hot and remain operational? Would this actually be within prudent
design parameters for the device? In theory if the caps are not actually
operating at even 85 degrees C then why wouldn't you be able to use a
lower rated temperature cap for that application?

It would seem to me that if a piece of equipment were designed to run a
capacitor that hot or even at 85 degrees C for whatever reason then in my
mind that would certainly constitute a very poor design. I have been
repairing TV's for many years and the only capacitors I've ever seen get
too hot to touch were bad ones. Could someone please explain this rating
to me? Thanks, Lenny

I'd take it to be the maximum recomended operating temperature - exceeding
that significantly reduces its life.

Apart from radiated heat from other components (like power resistors) the
main cause of heating is power dissipated in the apparent internal series
resistance; ESR, ripple current - especially high frequency in a SMPSU
constantly alternates between charging and discharging the "ideal"
capasitor, the current going in and out develops a voltage across the ESR -
AxV=W.