3 ms·
50Hz basically means the arc is extinguished after at most 20 milliseconds, limiting how much the contacts heat up. For DC on the other hand there's no guarante
by Doxin 6y ago
50Hz basically means the arc is extinguished after at most 20 milliseconds, limiting how much the contacts heat up. For DC on the other hand there's no guarantee the arc will extinguish at all. You can imagine how a sustained arc would be bad for a relay.
Of course a higher frequency would heat the contacts even less, and I imagine you could get a relay rated for even higher voltages given a higher AC frequency.
- amelius 6y agoBut arcs only happen when the contacts are almost-but-not-entirely closed, I suppose (ionization could be a factor). This time-period is, I suppose, very short, much shorter than the 10 milliseconds of the AC half-wave. I suspect the arc could cause the contact to stick for a while, which may increase the arc time.
- deleted 6y ago[deleted]
- Doxin 6y agoAt high enough voltages you get anywhere from second-long to indefinite arcing. Not to mention that the contacts are cost optimized, so the manufacturer would like to get away with as little travel as they can as to simplify the mechanism.