On Sunday 13 December 2015 16:39:16 andy pugh wrote: > On 13 December 2015 at 11:01, Gene Heskett <[email protected]> wrote: > >> Feed the cap bank through a resistor. > >> Use a (cheap $5) solid state relay to bypass that resistor when > >> LinuxCNC is turned on. > > > > I had largely discounted that idea because the first cycle surge is > > likely high enough to fuse a 40 amp Crydom. It trips a 20 amp > > service breaker instantly when its master switch is closed. That > > would also be complicated by needing a high side drive for it. > > The relay won't see the surge, because what the relay does is bypass > the surge absorbing resistor. > > The relay would go on the AC input side, so you would only need one. > > You don't need a "high side driver", you need a 5V signal from > LinuxCNC.
As I reported, I have 4 of them coming. But always curious. after I got my lady settled in from her cataract surgery this morning. I went out and attached a line cord to the one I had out, and which had the .004" thick hard paper shim between the poles. It darned near buzzed itself off the table when I plugged it in . So I took the shim back out, a bit quieter but still had an audible buzz I could hear from anyplace in the garage. I had noted a light film of rust on the E core faces, so I laid a worn piece of that 220 grit in a flat, and polished 75% of the rust away, noting that the center leg of the E was a thou or so lower than the outer legs. I sanded until I could begin to see a bit of clean steel thru the nearly black oxide coat on the center leg, and the outer legs were about 75% clean. Put it back together, could not hear anything but a very low level hum with an ear on it. Blew a couple feet of the concrete floor clean so if it blew up while I was back in here making preps for dinner, and left it plugged in for an hour. Went back out, E core temp up 3 maybe 4 degrees F, coil maybe 10F warmer. And still essentially dead silent. Now I wonder if thats the secret to shutting all of them up, because I could easily tolerate 2 or 3 of those running if they'd run that quiet. 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
