On 12/12/2015 08:32 PM, Gene Heskett wrote: > > As I'd druther not have to listen to those contactors humm & buzz when > powered by 120 AC, my thoughts are to use that transformer as a step > down, feeding the nominally (I haven't measured it yet) into a bridge, > feeding the contactor coils with somewhat filtered DC from that, which > ought to silence them. > > But I suspect that 90 volts (cap input filter) is still way too much for > those coils over any time period in excess of 2 or 3 minutes. > > So, how much more do I need to reduce the coil voltage in order to run > them at a reasonable temperature on DC? > > This won't work. AC contactors depend on the change in inductance when the armature slams home into the stator. So, they pull a lot of current when in the un-energized position, and then the current drops drastically when pulled-in. The only way to do this is to have an NC contact that delivers full current to the coil until it is pulled in, then opens to put a resistor in series with the coil.
Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
