Hello, Sotiris here! 👋
🚀 Today we´ll talk about thermal management and spot some pros/cons in the inductors we´re tested in the previous newsletters (if you missed any of those, you can find them here).
❓ Have you ever been in a situation where you’ve calculated this many watts in losses, then you choose a heatsink that seems appropriate, and in testing you found out that the power device is turning into a massive dying star, close to a super nova effect🔥?
Well that’s what an unexperienced engineer sees when he doesn’t take thermal management seriously…
I believe that no power electronics engineer can believe he’s got a good grasp on power electronics without him knowing all the basics of thermal management.
❌ Anyway, I’m not going to talk about thermal resistance of the junction-case, case-heatsink, heatsink-air today, that’s too trivial, and many engineers apply these concepts correctly.
✅ What is interesting for me is forced air cooling (with fans) of a heatsink, or an inductor-transformer.
The only question that matters: “By how many degrees °C, is the fan I chose going to bring down my heatsink in this assembly configuration?” 🔥
Fan selection process:
👉 Let’s say that the pcb can fit a 2°C/W heatsink. But the ideal one would be a 0.9°C/W. Two heatsinks with these ratings have totally different mass volume, thus dimensions. So, you want a fan to bring down the thermal resistance of the 2°C/W heatsink to 0.9°C/W.
👉 That’s a 55% adjustment of the heatsink’s thermal resistance.
👉Using this table below , we can choose a fan with 200LFM minimum. I’d go for a 400LFM and control its speed, if need be, just to have some room for errors. Better be safe than sorry…
