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I have a top mounted fan, which I take it is the norm. As a factory standard is it blowing air upwards drawing it out of the case or blowing air down into the case and across the fins?
Why isnt it for example mounted on the bottom and blowing air up, through and out the top?
Dunno - poor design maybe?. I was always taught to blow air into an enclosure for cooling, since the +ve pressure reduces the build up of dust, and if the thingy to be cooled is close to the fan you can benefit from the very turbulent air that comes out of the fan. I'm pretty sure my VFD has a fan (or maybe 2 little ones) in the bottom.
Yeh my XSY-AT1 VFD's have a fan on the bottom that blows air up, through and out the top the. The 3kw Huangyang has a top mounted fan that blows air down but the top mounted fan on my 2.2kw Huangyang blows air up?Quote:
Originally Posted by Voicecoil
Maybe the fan in your 3KW was mounted back to front by accident during manufacture? It certainly can't be the best idea as the hot air blown out the bottom would tend to rise to the top of the cabinet and get recirculated.
From an entirely theoretical point, 'sucking' creates a more even air flow, as atmospheric pressures causes more even air flow, than a fan blowing air through something.
This is why nearly all main vehicle cooling fans are behind the radiator, and it's not just a carry over from the days with engine driven fans where it was the most practical position.
However, in the realm of electronics and enclosures, people normally just throw enough airflow at cooling, as you're not likely to be chasing marginal gains.
Personally, I'd be happy as long as any cooling fan is assisting natural heat flow and not fighting against it, unless there was a specific reason for doing so.
Having a fan drawing air into the enclosure creates a rather localised fast air-flow that would increase the probability of drawing dust, dirt and chips into the ensure at high speed, and depositing this onto the PCBs/electronics. Drawing air out of the enclosure (exhaust) allows the sourced air to be collated from the various air inlets at lower pressure differential and is therefore less likely to draw detritus into the enclosure.
Chosing an exhaust solution - the logical positioning is on the top of the enclosure to remove the hot air at the top of the enclosure.
Regardless, the controller IP is poor on these and they need protection within an external enclosure - though I don't practice this myself.
I see your point, but I think you also have to consider what's best in terms of cooling. In something like a medium>high power VFD likely 90+% of the heat will likely be generated by power devices on the heatsink, therefore primary concern need to be generating a fast turbulent airflow passing over that, easiest way is fan at the bottom end with a baffle/wall over the top of the fins to stop the air taking a short cut. Yes, you could do this with distributed inlets and sucking, but it would then involve a certain amount of baffles/ducts to direct the flow to where it's needed, which would likely make the unit bigger.Quote:
Originally Posted by Doddy
The point about crap getting into the unit is a good point though, and makes @marbles 3KW unit sound even stranger, as taking in air from the bottom has to be the best place to avoid that. I put my VFD in the cabinet when I built it and even added mesh screens on the cabinet ventilation to keep chips/swarf out, and am heartily glad I did as the surrounding floor looks like it's been snowing aluminium at the end of a machining session.
I've not looked at my Huanyang VFD for a while, but the two WK boost inverters I've been playing with lately, the cooling fans only create airflow through the heatsink, so don't make any difference to how much dust/dirt/chips end up in the control electronics.
In terms of enclosures, as Voicecoil says, there are other considerations.
For dusty enviroments, I'd prefer to use a filtered fan blowing into and pressurising the enclosure to minimise the amount of dust being drawn in.
VFDs are generally designed to be placed in a clean enviroment/enclosure, so the location of the fan in terms of dust/dirt/chips isn't really a consideration. They're no different to your typical stepper/servo drives, in that regard.
Apart from the front panel controls, of course.Quote:
Originally Posted by m_c
Okay, that’s a bit divisive and to be honest I don’t think we can hold any Chinese vendor as a paragon of design excellence. For what it’s worth my earlier post was after 15 minutes of casual browsing on cabinet design on the axia ventilation/cabinet website, I won’t claim any personal insight.
Still, ask a dozen engineers and you’ll get 20 different viewpoints.
I’ve alleged to the fact that I don’t practice what I preach, my old star mill has a 3mm welded bracket bolted onto the column to accept the vfd with the original exposed inlets/outlets covered in a stainless steel micro mesh... though a redesign has exposed more of these and I need to sort them out one day