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Inductor current rating and temperature

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smbaker:
I have some switching power supply projects, and I chose this inductor, PA4309.104NLT, rated 3.5A. The issue I have is that I'm measuring it's temperature at around 130C with 1.4A going through it, and 190C with 2.2A going through it. This greatly exceeds the 125C rating of the inductor. Plus, it smells bad.

Datasheet says "The rated current as listed is the heating current that the part can withstand with acceptable temperature rise in typical applications".

So what am I missing here? It's not like one typically heatsinks an inductor, does one?

Scott

Circlotron:
Is the rating with forced air blowing on it? Also, some inductors can change their magnetic properties when they are too hot, but come good again when they cool down.

drussell:
How is the inductor being used in the circuit?

nukie:
Not some but all magnetics will lose performance so it's best to go up a notch with the saturation spec. Keep heat away from magnetics.

I am pretty sure inductors are not suppose to smell bad. What is the peak current at the inductor?

smbaker:

--- Quote from: drussell on March 30, 2019, 02:17:45 am ---How is the inductor being used in the circuit?

--- End quote ---

It's the main inductor in an LM2576 buck converter. LM2576 datasheet says to oversize by 20-30%, hence my choice of a 3.5A inductor. Perhaps I should have choose a greater value of inductance. I'm usually building 5V boost converters where the 100uH is appropriate, this time I built a 12V where 150uH or 220uH may have been more appropriate.

I can derate the circuit down to an amp or so and be within a more reasonable temperate. I'm just curious more than anything.

Scott

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