DC fan array

[tedmich]

So I have (2) 24VDC fan arrays that I've been using for >10 years to cool me and my stuff down.
Theyre made of (4) big Comair Rotron 23w 127mm fan arrays that push 700 CFM at full chat
and I've powered them with a variable output DC/DC converter and a AC to 300VDC front end converter (both Vicor units I got cheap)

The 100W DC/DC converter 300VDC->24VDC just died (it wasnt heatsunk) so Im rebuilding the unit

Im using the same 300W front end and a new 500W DCDC unit, purchased off Ebay for $30, in a solid box


these fans run OK from 12V-26V, which the Vicor will provide with a 1k pot and 2 resistors (they have calculators online)
I have a few of Vicor's new MUCH more compact front ends (same brick size as DC/DC ) but we'll see how the older unit lasts since I dont need the 700W the new front ends push.

(This control box shown above is cable linked to the 4x fan array while the other existing unit is all self contained and made of oak)

I'm planning to make an additional (4x) fan parallel array with some bigger 170mm Delta fans (860 CFM, 5db quieter, $14 ea new!) with a similar variable voltage supply but ran across this in the datasheet



so do I need caps somewhere?

If I had to do it over I'd use a 24V brick and PWM

[John_H]

Are they using the capacitors to dampen the inrush current from multiple motors starting simultaneously?

[tedmich]

Maybe? My oddball DC/DC power supplys introduce no noise ( audio equipment right on same plug) and I havent had an issues unless the inrush current killed my old 50W unit.

these are the new fans off Ebay, they are a great value, super powerful! https://www.ebay.com/itm/114353530158
and about 15% of their list price ($85)

with the Orion "low noise" fan grill G172-10LN they are very quiet as well

[John_H]

I was thinking that the voltage drop from the inrush might be enough to shut down the MOSFET