"RobertMacy" wrote in message
newsp.xjc24hpo2cx0wh@ajm...
On Mon, 21 Jul 2014 11:18:07 -0700, 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

46C? and 50C no biggie

transformers are passive devices and made out of 'material'

easily take 65C, that's 150F

you may be running your AC mains at 125Vac instead of the 115Vac, which
will make them run just that bit hotter to where you noticed.


One thing the OP failed to state is the voltage of his 20 amp power supply.
2000 volts at 20 amps is a much larger transformer then one might find in a
12 volt, 20 amp supply.