"Fred McKenzie"

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.


** FYI there is a much simpler, low tech way to find the internal temp of a
transformer.

1. Measure the primary winding's resistance when at room temp.

2. Make the same measurement ( quick as you can) when the tranny's running
temp has stabilised.

3. Calculate the increase as a decimal factor and multiply that by 254 to
get the temp rise in degrees C.

Eg.

Room temp = 4 ohms

Hot temp = 5 ohms

Increase factor = 0.25

0.25 x 254 = 63.5 degrees C

Add on the actual room temp to get final result.

If the number is over 100C there is cause for concern.



..... Phil