Thank you all for the amazing support, this is becoming a master class for me personally...Quote from: madires on 20 May, 2024 15:35Quote from: v0ltair3 on 19 May, 2024 18:23This is how I wire it, but it blew the 1A fuse that I had in the input upon connecting it to mains. Transformers have a high inrush current which can be multiple times the normal current draw. For smaller transformers use a slow-blow/time-lag fuse rated a bit higher then the normal current draw. For larger transformers, which could trip the mains circuit breaker, the best solution is to add a soft start circuit. And as already mentioned, the transformer could have a fault when blowing a reasonably rated fuse.Quote from: v0ltair3 on 20 May, 2024 14:213- Is there a way to understand why the fuse gets burned when I add the jumpers? Could it be that it peaks at the start and therefore thus burns the fuse? (I used a 1Amp and a 2Amp)The transformer has two primary windings and the jumpers connect them in parallel, i.e. higher current draw and higher inrush current. Based on the transformer's max VA rating I'd would try 6.3 A.Using a slow 5A fuse it holds
Quote from: MrAl on 21 May, 2024 04:37Yes you can sometimes run a transformer in reverse, but the excitation current may be different, or inrush current could be higher, so you'd have to check for that.Is there a way to verify that? The only thing I notice is that I connect in the normal operation I get 0.4A, and in reverse about 0,6A, I don't really know how to interpret this fact... The only drawback I see is that if I use it normally is that I get almost 248 (18v above the normal) out of the above secondary, and in reverse, I get 220v out of the bottom part, so I would rather stay as close as possible to the 230v. Btw, is it better to be above or below the reference voltage? Quote from: MrAl on 21 May, 2024 04:37Ok if those voltage measurements are correct, then it looks like the two windings in question are the same voltage and the same phase, although the resistances look slightly different but that could be just measurement error. If the resistances are not the same then one winding will put out more power than the other, but the difference isn't that big.Measuring it by connecting 20-23 and 26-28 I get basically the same thing our of the secondary, so I don't believe it will make such of a difference. Quote from: MrAl on 21 May, 2024 04:37If you only need 1 amp you should be able to get that with just one of those two windings.As to the fuse blowing, was it a fast blow fuse or slow blow fuse? A fast blow fuse would probably blow with this larger transformer, with a slow blow it may not blow but only 1 amp probably isn't high enough.1 amp only requires around maybe #22 AWG wire, maybe #20 AWG so you could check that as those lead wires are quite visible.It's actually 1mm^2 without isolation, so It would be able to hold way above 1 ampQuote from: MrAl on 21 May, 2024 04:37Another question would come up too though. If you intend to use this as an isolation transformer, you should probably read up on isolation transformers and their specifications. You would need to check for leakage from input to output, and if there is a problem with the old insulation that could be a problem which brings the issue of safety into question.I had an old oscilloscope a long time ago, but it was even old back then, and one of the high voltage transformers had high leakage. I went to measure a point on a calculator PC board while the calculator was powered up and a spark jumped from the probe tip to the calculator. The calculator was nonfunctional after that, so the spark blew it out. That was a nice calculator too loved the display it was vacuum fluorescent. Never found another one like it.I had to replace the transformer with three other lower voltage transformers as I did not have one with a high enough voltage to run the scope. To bad it was too late for that beautiful calculator.When it comes to human safety though that's an even bigger issue of course.How expensive these days is a brand-new transformer of the type you need if you were to buy a new one? 1 amp current is not very much current.What I looked was at continuity between all the primary and secondary windings as well as the transformer metallic support, and it's an open circuit between all of them. Is there any other measure I could do to ensure I don't run into safety issues?Again, thank you so much of all your support!