"WindsorFox[SS]" wrote in message
news:%bYZa.9210$qf.2506@lakeread06...
Trevor Wilson wrote:

**Oh, yes it is. Modern 12VDC fans use an internal oscillator, driving a
3
phase, brushless motor. The only proper way to control the speed is to
vary
the frequency of the internal oscillator. That is a difficult thing to
do,
given that the circuitry is embedded.



Obviously you refer to somethin other than 12 Volt computer fans.

**Nope. For such a cheap, ubiquitous item, they are surprisingly
sophisticated. It was not always so. 12 Volt fans did use brush type motors,
but their MTBF was significantly lower than modern fan motors. I know of no
modern fan motor which is not a brushless type. Some may still exist, in
VERY cost sensitive computer equipment. No sane engineer would specify them,
IMO.


--
Trevor Wilson
www.rageaudio.com.au