AVR-Chat

David VanHorn Wrote
>The voltage ratings on switches are similar to those on fuses.
>Above that voltage, the switch is not guaranteed to be able to break
>the circuit.
>This has to do with inductance in the load, and for a large enough
>inductor, no reasonable switch will work.

That's part of it, but not the whole story.  You will find that most small
switch ratings are for non-inductive loads.  The other limiting factor is
simply the air gap between contacts and how fast that air gap opens.  The
smaller that air gap and the slower it opens the lower the voltage rating. 
If you exceed the voltage rating you are more likely to draw and sustain an
arc thus negating the actual switch and this can happen w/o needing
inductance.  Inductance simply boosts the available voltage enhancing the
possibility of arcing.  This is also somewhat current dependent so some
switches (fewer than I would like) will provide different current ratings
for different DC voltages.


Of course some arcing is actually required for power switches.

Robert

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