I've actually done this. I took a cheap 12 volt "wall wort" power supply and crushed the plastic case in a vice and salvaged the little 1.0 amp 12 volt transformer. Then I place 120 volts AC on the 12 volt side and no I did not get anything like 1,200 volts out. It was more like 300 volts because of the copper and iron loss.
But no fireworks and no core saturation. Core saturation is determined solely by the current and if you are drawing only about 100 milliamps the core is doing just fine and is within its specs. This way-cheap 300 volt power supply has been powering a vacuum-tube based guitar overdrive effects peddle for many years. The backward wall wort is big enough to run a 12AX7 tube with about 300 volts on the plate. The whole thing is inside a grounded aluminum box, so it is safe enough. You can run any transformer "backward" as long as you observe the current limits of each coil. But watch it when building stuff that uses high voltage. Think twice about how a part can fail. The goal is that it must remain safe, even after multiple parts fail after it does catch fire, so there are a few rules to follow. On Thu, Jun 17, 2021 at 1:03 AM Gene Heskett <ghesk...@shentel.net> wrote: > On Thursday 17 June 2021 01:20:51 Roland Jollivet wrote: > > > If you have some transformers lying around you could stack the > > secondaries to get 440V > > They don't need to be step-up, just sum the secondaries. You need to > > have them all in phase obviously. > > > > Then use a small, single phase 440V VFD > > Most VFD's under 1Hp accept single or 3ph, but I don't know about > > 440V. Maybe 380V > > > > I don't know if you can use a 110V:24V transformer in reverse, or > > whether you'll cook it. Worth a try... > > > No, it not unless you like fireworks. Applying 127 volts to a 24volt > winding will saturate the iron and the inductance will go to nearly > zero, allowing huge currents to flow. > > > Roland > > > > > > > > > > On Tue, 15 Jun 2021 at 00:36, Gregg Eshelman via Emc-users < > > > > emc-users@lists.sourceforge.net> wrote: > > > The motor is in a Hardinge UM mill, less than 1 horsepower. It > > > cannot be switched to 220V. Any way to get it running off 220 volts, > > > three or single phase, without breaking a few banks? > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > 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) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
