> In 2xMR154 module, I use two 48V/145CFM Fans from Mechatronics. They
> are PWM controlled by the microcontroller and mounted on the top of
> the finned part of the heat sink. A third fan 100CFM is right on the
> top of the output transformer and it is controlled by the same
> controller as the first two.
Three fans and a microprocessor to cool one heatsink and one
transformer. Talk about exaggeration!
> This arrangement keeps the die at only 120C forever when running full
> 1500W.
So would a single fan with no CPU.
> About noise. The more noise your fan is doing the better you are off
> as it is an indication of air movement . If you want a quiet Fan you
> will have to reduce the amount of heat generate and implicitly your
> output power. Certain Thermodynamics laws can not be circumscribed :)
> FANS DO NOT PRODUCE NOISE! AIR MOVEMENT DOES!
In fact most noise is caused by bearings in the fan, turbulence in
the impeller, and at times from turbulence in the device the air is
forced through. Some fans and blowers have poor balance, but that
mostly causes a low rumble.
There can be a tremendous difference in noise at the same airflow.
One example is the Ten Tec 811A amplifier, where they unwisely
stuffed the muffin fan against large objects. This increases noise
drastically and reduces airflow significantly. A fan or blower will
generally become noisier when airflow is restricted.
73, Tom W8JI
W8JI@contesting.com
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