Transformers have a current limit due to the thickness of the copper wire= - if it has been properly designed this will be matched on the input and output to give the same VA rating. They also have a limit due to the magnetic circuit. If you look at the output on an oscilloscope you will see a sin wave. Eve= n if you overload the electrical limits by taking too much current through = the windings you will see a sin wave. If you overload the magnetic circuit it will saturate and the tops of the sin wave will start to sqaure off. So this is another approach you might try, apart from seeing if it gets t= oo warm. I don't know which limit will manifest itself first, all things bei= ng equal and the design being right I would suppose that they will appear together, but they might not. Hope this helps....Mike. ----- Original Message -----=20 From: "Carlos A. Marcano V." To: Sent: Saturday, January 08, 2005 5:59 PM Subject: [EE] Finding out transf power capability Hi list. I have recently gotten in my hands a bunch of simple power transformers (one prim, one sec). They are of various sizes but have no id on them. I would like to know if any of you could point me to a way of testing them = to find out the ratings of their power capabilities. I think they are all fo= r 110 VAC primary, but I=B4m clueless about the sec rating. Is there a way = I can do this without melting them (try and error approach)? TIA, Regards, *Carlos Marcano* -Guri, Venezuela- --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 Outgoing mail certified virus free. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.6.9 - Release Date: 06/01/2005 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist