On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like
degrees F, anymore. Please learn the Metric system.

--
Trevor Wilson www.rageaudio.com.au