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Old 22nd Feb 2021, 8:11 pm   #6
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 2,378
Default Re: Running DC brushless PC cooling fans

I've done quite a lot of experiments with speed controlling brushless fans, and it's quite easy to wreck them with fairly mild overvoltage. For a 12V fan, a supply of 19-20V is already in dangerous territory. The reason is that they have an internal controller chip (or, sometimes, just a couple of transistors) which has a pretty strict upper voltage limit. Exceed it and it's game over.

What's going on in the workshop?
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