Archived from groups: alt.comp.hardware.homebuilt (
More info?)
> I just tried this with two Panaflo 80mm. It was quite interesting to
> watch.. there would spin for one second then stop, then start, then stop,
> then start spinning properly.
Panaflo use a stop/timer/restart motor stall management function.
NMB also use it on some fans (Minebea/Panaflo are now merged so you
will eventually see a broader Panaflo range - including S model & 38mm fans).
EBM-Papst use a different system - and so don't "do the dance"
Fans vary quite a lot in their operating range re intended market:
o Industrial fans typically 9-15V, 7-13.8V, 9-13.2V
o Higher speed fans a) have a narrower range or b) lower life at T-Max
A voltage range of 10.3-13.2V indicates a 24V fan rebadged as 12V for example.
Some fans have a very wide operating range - industrial 172mm fans I use tend
to have a 16-36V range, and one has 10-38V range despite being 24V nominal.
PWM will let you use an "exact" 50% cycle, in some cases 45%:
o The risk is you can end up with PWM noise
o They ensure starting by running the fan at 12V to ensure starting
Bearing design is also a factor in spec voltage:
o Typically ball/sleeve grow in noise over their service life
---- sleeve by 15dB(A) at T-Max over 1yr (if they even last that long)
---- ball by 5dB(A) at T-Max over 1yr
---- NMB ball by 3dB(A) at absolute maximum at T-Max over 1yr
o Fluid dynamic & top hydrodynamic bearings don't grow in noise
---- the disadvantage is they are not ideal at super-high rpm in fans
-------- unless you wish to pay 35$£/fan like some laptops use
---- in instances where you need say >6000rpm you use NMB ball
-------- an example would be a B8* or B7* model - special screamers
Anyone who has suffered a Dell which switched to full speed knows
If you think the old Apple 57dB(A) & 69dB(A) were bad, think again.
> Presumably 6V was borderline for thse fans and the Resistance of the fan
> drops when it starts spinning, hence the little performance before starting
> up properly?? I assume if one failed the other might stop???
The fan detected stall & reacted to it - and in doing so it can cause a series
connected fan to also go into stall. It depends on the exact model, and a 6V
supply is actually below spec - a 7V operation is more reasonable.
Yes if one fan did fail (rare re electronics) it may stop the other fan,
just like having 2 light bulbs in series, if one fails, other is not lit.
7V is the simplest system, although in some instances two inline is ok.
--
Dorothy Bradbury