Does any one know how to predict the temperature rise for the following core given a particular power loss?
Digikey PN: 495-75921-ND
Tried the following with a power loss of about 9 W and surface area of about 30 cm^2 and only got a temperature rise of about 2 degrees C:
In case the link does not work:
TR_C = (total power loss(W)/surface area (cm^2))^(0.833)
Checking to see if there is something more accurate preferably from TDK.
What numbers did you stick into that equation? I’ve a suspicion that you may have gotten some units mixed up.
As a sanity check, the result you mention would suggest an aggregate thermal resistance of 2°C/9W=0.22°C/W. Compare the approximate size of your transformer/core to a heat sink with a similar natural convection thermal resistance rating; the 510-14U (0.21°C/W) measures roughly 7x14x3 inches, compared to roughly 1 inch cubed for that core with a bobbin. Is a ferrite core stuck in a bobbin going to be as effective at transferring thermal energy to the surrounding air as a purpose-designed heat sink that occupies some 250x the transformer’s volume? I’m guessing not.
I haven’t found a better resource at this point, and don’t have enough time in topic to be able to offer a ballpark figure off the top of my head. A person could look around at similar products/items based on them as a means of calibrating one’s expectations, but insofar as it’s a thing that’s going to have some application dependency and call for empirical verification eventually, building and measuring a test device may be a worthwhile exercise.
I just now see what I did wrong.
Total transformer power losses is supposed to be in units of mW vs W.
If i change total power loss from 9 W to 9000 mW I get a temperature rise of 506 degrees C.