On 2 October 2013 18:28, Jon Elson <el...@pico-systems.com> wrote: > If this is the case, the contacts will still be welded, so open up the > relay and examine it.
I will, but as I still have the welded relay from last time, I think I know that it can happen. > Normal relays are severely derated for DC, and breaking 300 V > DC cannot be accomplished by any standard relay. It probably doesn't take > a glitch on the mains, just after so many on/off cycles, you will get a > failure as the contacts degrade. The relay should never even try to _break_ 300V DC. It _makes_ 300V DC to discharge the caps, but should only ever break when the caps are at 0V. > or use a FET to control the dump resistor. I would like to do this, but I am not sure how to wire a FET to discharge the cap when AC power is removed (Whereas an NC relay does this easily) I though of using the fact that Thyristors latch on when current is flowing, but then I think I run the risk of restoring AC power while the device is still conducting, with the same result. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
