Time for a new Warpinverter build

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Warpspeed Guru Joined: 09/08/2007 Location: Australia Posts: 4406	Posted: 08:21am 13 Mar 2021         rogerdw said   That leads me to a new question then. I am wondering what is an expected top temperature for one of these transformers once they've been rewound? There is no simple correct answer to that. I suppose it depends on the temperature ratings of the wire, and any other insulation. The very best grades of wire can be rated up to 200 Celsius absolute maximum. The hottest part (hot spot) will be buried inside the windings, and can run a lot hotter than surface temperature. I suppose if it feels too hot, and there are hot smells, that is probably getting pretty close to what I would consider acceptable, but that is just my own rather conservative opinion. Quite often a full transformer specification will include a temperature rise figure at full continuous rated power.  There are also industry standards for various applications in different countries. Its all a bit of a grey area really. I personally do not like hot smells which usually start at about 80 Celsius surface temperature.  And that applies to heatsinks as well as wire wound resistors and transformers. There is a secondary issue here as well. Something that gets very hot may work perfectly well, but it may cause long term reliability issues for other nearby more sensitive electronic parts. If you stick with the recommended current density in the wire of four amps per mm square, that will run continuously like that without excessive temperature rise, and at considerably more for short bursts. So once you have worked out your wire sizes that will fit the core, the current density figure x mm sq x voltage will give you a nice conservative transformer power rating. Edited 2021-03-13 19:13 by Warpspeed