09-12-2019, 02:44 PM
(08-12-2019, 09:47 PM)Amie Wrote: Thanks Mark. Yes I understand the snubber across the contacts, but am surprised that just a capacitor is used. If you happen to close the switch at peak mains, it must arc(Shorten the life of the switch), or is it just the best of a bad choice. I have seen those capacitors wired L to N that have puffed out what appears to be stinky steam?
Amie
Yes, while an RC network is best, a single C can work.
Will it shorten the life of the switch?
It depends. How much worse was it with no cap?
Of course, the arc caused be the capacitor depends on how much energy was in the cap, and that depends on luck, basically. While it's possible to get very theoretical about snubbers - and sometimes that's necessary - a lot of them are just plucked out of thin air. But then, rules of thumb are often good enough.
You're thinking of the infamous RIFA X2-rated caps - paper dielectric sealed in a resin case. All fine until the resin cracks and exposes the innards to the atmosphere. Paper, of course, is hygroscopic. There's a lot of moisture in the air!
https://lanas-kenwood-spares.co.uk/wp-co...-BOARD.jpg
The trouble with the smoke from these is the deposits, which can be hard to clean up. I dread to think how bad the fumes must be for us!
The real fun is when those caps are embedded inside those filtered mains inlets:
https://www.vintage-radio.net/forum/show...hp?t=88137
Often with no fuse protection beyond what's in the mains plug, as the equipment fuse is normally downstream of the filtered inlet. And because of the potting compound, the explosions are often more violent. Not good!
