Monday, September 26, 2016

SSPA Power Supply - Heatsink/Fan for Final Diodes

As mentioned previously on this blog one of the issues noticed during the most recent load testing of this power supply was the final protection diodes got quite hot during a 62 amp load test on a single bank for 4 each 13.5 vdc supplies providing 53 vdc (after the diode drop) in series.  I measured at least 150F on them possibly as high as 180F.  These diodes have a max temp of 150C which equals 302F.  So it wasn't catastrophically hot.  But hot enough to want to try to manage it better than doing nothing.  

I had initially thought I would put some thermal paste under them and bolt them onto the case bottom.  However, since I had some spare parts to do better than that I decided to opt for something a lot more robust.

I had some spare heat sink material and I have a lot of spare computer fans around so I decided to try to mate them up and build to identical heat sink setups for each set of diodes.  Each bank of 4 supplies in this (there are 2 banks) has a dual diode at the end before both banks merge into a single output.  This is to keep their output separated from each bank.

So here are some photo's of what I came up with.  I still have to apply the new thermal paste under them, and make some new cables to run to the output terminals, but I was able to get things migrated around in the case, and the completed heat sink / fan combos built and installed this past weekend.

These fans blow INTO the heat sink instead of sucking out of them.  This forces most of the air UP the fins and out of the case through exhaust fans at the top of the case.

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