On Friday 12 June 2015 22:06:16 Jack Coats wrote: > Yes Gene, there is no santa clause, especially when you are talking > about copper. Just as a raw material it is pretty pricy. > > In the past I just got a couple of matched transformers 120VAC to > whatever, and put the secondaries together. > It makes a good isolation transformer when set up back to back. > At double the iron & I2R losses though. I'd druther have it on one core.
> Good transformers are never cheap. Depends. When Peter Dahl was winding stuff for us broadcasters 20 years ago, I thought he did a quite reasonable job of selling me a modern, grain oriented steel core replacement that was 1/2 the size of the original that smoked, the smaller size made possible by the improved steel for laminations compared to what was in the originals in 1956, when I needed it in 1999. I fully expected to have to pay twice what he asked, considering he was winding it from scratch using the old GE drawings. And he had it on site in 4 days! I am well aware of that lack of a Santa Jack, but we're talking about a couple kilowatts worth of iron & copper to have a CCS rated setup. I don't mind paying some north of a $150 bill, but even at that, the selection on fleabay is limited, or poorly described. One 1.5kw toroid looked promising, but the guy may be blowing smoke, no way to tell from his description. I might send him a msg tomorrow to see if he has any more data on it. Good sized, weighs in just short of 40 lbs, so I don't doubt the 1.5KW rating. But the windings description is sorely lacking in details. Heck, something out of an old microwave wound on an EI core could probably have the high voltage winding recycled & replaced with 8 gauge enough for what I need. Some stepdown, say 25-30% would be ok as I'd like to have about 105-110 volts out of a bridge rectifier into a 75,000 uf cap or 2. Those I have several of already. Surge rated at 150. They seem to tolerate the back dump into the supply when slowing that 1 hp motor ok. If I sounded like I was looking to get lucky I'm sorry. > On Fri, Jun 12, 2015 at 6:09 PM, Gene Heskett <[email protected]> wrote: > > Hi all; > > > > In laying out how I am going to cnc this GO704, its apparent that > > the scr or triac board it comes with to control a motor of > > undetermined power, rated variously as 750 watts, 1kw, or needing 12 > > amps from the line. None of which groks, but welcome to chinese > > specs seems to be the operative response. :) > > > > Anyway, since Jon's pwm servo amplifier worked so well on my lathe, > > and its theoretically capable of that sort of power (20 amps at 160 > > volts IAACS), my mind is made up to use it again. But its I/O is > > not all isolated so it must have an isolated power supply. > > > > But 1kw and up isolation cans are both scarce, and north of a $100 > > bill pricy at least on fleabay. > > > > Has anyone got something laying around getting dusty that could > > serve as a 120 to 120, or 240 -> 120 isolation, and that you might > > be able to part with? I have 240 just 7 feet away from where I have > > it parked so a stepdown would work just as well and would help > > balance the load. > > > > Send me PM's with what it is & how much you'd need and lets see if > > we can deal? > > > > Thanks. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
