> From: Gene Heskett [mailto:ghesk...@shentel.net] > On Saturday 04 March 2017 16:24:29 Jon Elson wrote: > > > Thyristor? Really? I didn't know they put these on Bridgeports. > > (I've seen them on very old Fanuc controls, before 1982, I think.) > > > > You may have real problems finding replacements for them. > > > > Jon > >
Good news, they're actually still available in the correct package. The price makes me shudder. Better news, the thyristors are actually OK on this board. The actual damage was hidden under a warning label, at the minimum one capacitor has gone (I'm still deciphering the schematic, but I think it's part of an integrator). It may have taken a pulse transformer with it, so if I can source replacements I'll probably replace all the caps and transformers in that area. > I think they may be still around, at places like graveyard electronics and such. > Just hearing the word took me back a bit, primarily because while intended > to be bi-lateral, handling the fwd phase and the reverse all in one package > that the differences in trigger sensitivity were never fully understood by the > driver designers. Eventually they would get so lop sided that the dc average > that represented would saturate the iron in the inductances, leading to just > such a blowup. Interesting - I have to admit I'm still a little bit confused as to how these drives work, running 360V AC to the chokes and somehow turning that into 140V DC seems... odd. > I don't know that Jon's Pico Systems pwmservo driver at 20 > amps and 160 volts is a match for those motors, but if they are, those are > certainly great drivers. I had looked at the pwmservo as a backup option - it looks like a great drive. I don't think I can get a PWM output from the 7i77 though, and would need to build a new power supply for that drive. If I was to go down that route I'd probably replace all three drives - but it's a bigger change than I want to do. > And even bolted to a heat sink, they are probably > 15% of the cubic volume of the thyristor driver. I am using 2 of them, driving > 1hp brushed motors as spindle motors.. They Just Work(tm). I had to make > power supplies of coarse, big ugly kilowatt plus, 30 lb analog hogs. > > Cheers, Gene Heskett ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
