On 12/10/2013 3:18 PM, Gene Heskett wrote: > On Tuesday 10 December 2013 14:55:24 andy pugh did opine: > >> On 21 October 2013 18:21, Les Newell <les.new...@fastmail.co.uk> wrote: >>> A trick to get around this is to use a 24V transformer to buck the >>> mains down to 216V. Add the voltage doubler after that and your DC is >>> spot on. >> You seem to understand transforners :-) >> >> I am wondering what I can do with this one, that I found in a skip. >> >> Ideally I would like a 100V isolated supply, just to be a bit less >> scary when messing about with servo motors. >> (Rectified UK mains is 300V + ) >> > Or about 215 volts rms, 50hz I assume? > >> This is the label on top: >> https://drive.google.com/file/d/0BxjJW1-T6n7Cd2FrOWV5R3dRZnFhV2xrV0F3OHp >> 3UW05X2NF/edit?usp=sharing > This label can be a bunch ambiguous. But with the top wired in parallel, > feeding one side to terms 39 and 37, and the other side to 36-38, one would > assume the secondaries can then be probed to see which could be used to > obtain the voltage you need. > > Basically two warnings apply. Don't "seriously" overvoltage the primary > else the iron will become saturated magnetically at the peak voltage and > when that happens the input current rises dramatically and heating > destruction can occur. I see it has a 1050VA rating, or nominally 1 > kilowatt in round figures. The iron saturation point isn't a generally > published spec but can usually take a 15 to 25% overvoltage condition in > well built transformers. I ran my mill for years on an old tranny from a > 2" tape machine, feeding the 127 volt primary voltage we get here in the US > of Hay, to the primary terminals labeled for a 90 volt feed, in order to > get 29.5 volts for the motors out of the 24 volt winding when using a choke > input filter. No noticeable heating of that 50+yo well potted hunk of > iron, but that is "pushing the envelope" looking for the smoke vent with > more modern iron. > > This transformer in the pix, can also handle a nominally 440 volt feed by > shorting 37-38 together, and feeding the line rails to 36 & 39. This would > divide the secondary voltages by 2. > > They could have labeled it better though, and I doubt if an English label > would remove any of the ambiguity. If that was available as surplus, I'd > take a couple of them. > > Cheers, Gene
Good point about saturating the iron via overvoltage. That probably explains why I melted some 14 gauge wire several years ago.. in a "test connection". Andy said he got the transformer out of a "skip" which I believe translates to "dumpster". As in dumpster diving. A sport in which I am well versed. ;-) Dave ------------------------------------------------------------------------------ Rapidly troubleshoot problems before they affect your business. Most IT organizations don't have a clear picture of how application performance affects their revenue. With AppDynamics, you get 100% visibility into your Java,.NET, & PHP application. Start your 15-day FREE TRIAL of AppDynamics Pro! http://pubads.g.doubleclick.net/gampad/clk?id=84349831&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
