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| 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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