Greetings folks; I have managed to source ancient motor controller box, originally intended to serve as a bidirectional motor controller serviced by a 3 phase circuit.
It has 3, but I'll remove one, 3PST contactors with what from the schematic would appear to have 120 volt AC coils. They measure a bit north of 200 ohms. Also a step-down transformer to deliver 120 for the contactor coils from a 220 volt 3 phase feed. But someone has lifted the transformer out of the circuit and rigged it to run the coils from 120volt/ground. From the looks of the input cable, my guess is that is was simplicated for single phase 220 before it was removed from service and scrapped. 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? I have some other toroid trannies that might be more suited for this as I suspect the operation from DC can probably be reliably done with 30 volts w/o baking the coils. Does anyone else have similar experience who can toss a few words my way on this? Thanks all. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Some mill pix are at: Genes Web page <http://geneslinuxbox.net:6309/gene/GO704-pix> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
