Electronics > Beginners
Is it a bad idea to underpower a DC fan?
(1/5) > >>
solderfreelead:
I was wondering if it's a bad idea to underpower a DC fan, basically driving it with a much lower voltage than the labeled operating voltage.
Or if there's even such a thing as "underpowering a fan"?
For example, I have several 12V 120mmx25mm PC fans. They just barely start at 5V but once stabilized they seem to run just fine without any weird noise or anything obviously wrong.
Zero999:
The only concern is the fan might not reliably start, especially as it gets older, gathers dust and the bearing becomes stiffer. It might also be a problem at lower temperatures, although the fan might not be needed if it's cold, so that could be a non-issue.
tkamiya:
A DC motor draws more current when it's not moving at too low of voltage than moving slowly.  Also, inside DC motor, there is a set of brush that alternates between winding.  So under normal circumstances, duty cycle for each winding is 50%.  When not moving, a winding spends 100%.  I have seen a motor under this condition overheat and emits smoke.

If it's rated for 12V and it's barely moving at 5V, then I'd go with 8V or so.

Another option is to use properly rated fan or power supply.  Even high quality quiet fans are pretty cheap these days.  As to under powering fans, there are commercial product like that....  Auxiliary PC fan with high/low switch.
TheHolyHorse:
That's how the fans are controlled in a PC (unless you control it with pwm). So as long as it spins like other answers explained it will be fine.
SparkyFX:
These are usually BLDC with external commutation built in. If the electronic starts the motor at 5V, there is no reason for them to have a problem. I also run some on a PWM output on a fan controller, which makes them occasionally emit some noise. An electrolytic cap parallel to the fan kind of solved the problem.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod