On 03/24/2013 02:30 PM, Jamie wrote:
amdx wrote:

that looks like a linear semiconductor controller - an incredibly
antiquated concept for a modern car.

well, you live and learn. apparently the reason they use a linear
controller is because it allows the fan to run near silently at low
speed. with pwm control the fluctuating magnetic fields in the
motor coils cause it to vibrate and make a humming noise at the pwm
control frequency.

that doesn't of course get around the fact that the unit in question
here is apparently badly under rated, but the above does at least
explain why it's used.

I see many Motor Speed Control Manufacturers upped their PWM
frequency to be between 16 K to 22 K to eliminate much of the noise.
Mikek
Sure, if you don't mind heating the motor up...

Jamie


good point - how much? sure, big motor coils, big inductors -so how to
balance against pulse frequency for a bigger motor like a blower fan?


--
fact check required