Electronics > Projects, Designs, and Technical Stuff
capacitors across switches?
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coppercone2:
The art of electronics says you should put a capacitor across a mains switch to reduce arcing (x rated).

Has anyone seen this done before? I am guessing a capacitive short over the switch contacts.
BravoV:
A cap (+resistor) across the switch form a snubber that suppresses arc and prolong relay contact life -> Keysight AppNote : Maximizing the Relay Life Span

coppercone2:
have you ever seen this used for a mains switch?

here is a good document found as arc supression

https://www.illinoiscapacitor.com/pdf/Papers/spark_suppression.pdf

does anyone have the master document
1965 [4] C.C. Bates, Contact Arc Suppression of Electromechanical Relays,

T3sl4co1l:
Consider the RLC network formed by the mains inductance (~250uH typically), load (much more, ~mH to H for transformers), and whatever capacitance is around (mostly the load, low ~nF for transformers?).  The load current at the instant of turn-off, and the mains voltage at the instant of turn-on, sets the initial condition for what follows when the switch changes state.

To dampen either event, an R||L in series (switch closing, dI/dt limiting and current damping), or an R+C in parallel (switch opening, dV/dt limiting and voltage damping) can be used.

And since we're considering the source-load system as its RLC equivalent (for short time scales), the value of R, L and C required to provide this damping are easily derived. :)

Tim
coppercone2:
http://www.academia.edu/23402750/Power_Contact_Arc_Suppression_An_Investigation_into_the_Relative_Effectiveness_of_Snubbers_vs._an_Engineered_Electronic_Power_Contact_Arc_Suppressor
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