HV DC-DC converter?

[PVorBust]

Looking for an easy solution to power a (say 120mm muffin) fan at a remote site.
Currently the setup is 100V from PV's that only feed a pump controller, so no batteries, no low voltage.

Obvious solutions start with a DC fan, but I've never seen one
Next is DC-DC converter with a suitable input range, but they are hard to find
Meanwell do have a range with 40~160VDC input, but finding one to buy is another story.
I'm not fussy about the output - any of the common outputs would be fine (12/24/48V), I'll find a fan to suit

My suspicion is many mains intended SMPS would work fine off DC as the first stage (after filtering) is a bridge rectifier.

Before I go down that path, is anyone using a more elegant solution?

 

[wpns]

You mean like https://www.amazon.com/MEAN-WELL-RSD-30H-12-Isolated-Converter/dp/B0748LL7W9 Also DigiKey, Mouser,
https://www.aliexpress.us/item/3256803459080345.html if you want to take a chance

 

[efficientPV]

I use switching power supplies to power 12V fans. I think it is elegant. You get full isolation and if the supply shorts it won't destroy the fan or anything else. I am very leary of many buck converters.

 

[MattiFin]

Digikey has bit over 6000 possible matches with input voltage range between 88v and 750v and over 500 different models in stock:

Power Supplies - Board Mount | DC DC Converters | DigiKey Electronics

DC DC Converters are in stock at DigiKey. Order Now! Power Supplies - Board Mount ship same day

www.digikey.com

Search filters should help you to narrow down the selection.
One example that looked promising: https://www.digikey.com/en/products/detail/mornsun-america-llc/PV50-25B12/22035956
80...750V input voltage range, 50W 12V output

 

[zanydroid]

I use switching power supplies to power 12V fans. I think it is elegant. You get full isolation and if the supply shorts it won't destroy the fan or anything else. I am very leary of many buck converters.

Yep. I don’t know why AC is such a dirty word sometimes vs going all DC. It is mandatory to have isolation stage in this equipment.

My suspicion is many mains intended SMPS would work fine off DC as the first stage (after filtering) is a bridge rectifier.

Before I go down that path, is anyone using a more elegant solution?

I think this is a decent idea, one thing I’ve heard is that you should derate by 50% because only half the rectifier is in use, and the heat dissipation pattern is very different

And it will be isolated since the HF isolation transformer is typically still in there

 

[Vigo]

This buck converter looks like it would do the job for $15 and will even tolerate MUCH lower input than 100v and still function.

 

[AntronX]

You can take simple 120Vac/12Vdc switch mode adapter and run it on DC. Should be good up to 180Vdc. Not sure how it will behave at low input voltage at dusk/dawn.

 

[SpongeboB Sinewave]

FYI, to add to your list of possibilities, there is a company that makes DC (and AC) fans for greenhouses etc. That will run off of solar and batteries.
We have used them and worked with this company years ago. They are not cheap though.

Residential and Industrial Cooling Systems | Fogco

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fogco.com

Not sure of their highest voltage but they do have 24V fans.

boB

 

[efficientPV]

SMPS generally work down to 60V or less. Below that they will bump unless the startup resistor is changed. I have one that works down to 17V. Best to oversize a little because of higher input current. With fan demands of less than a watt, they will be working before and after anything else.

 

[Supervstech]

My smith electric box truck came with two 360VDC to 24VDC chargers for the onboard batteries.

 

[PVorBust]

Thanks for your replies.
One approach I've used elsewhere is not to tap into the "big" system, but simply add a dedicated (say 30W) panel and 24-12V DC-DC to spin a fan when ever there is light. I've installed this style in my workshop to stop is baking in summer (it would often get to 60C in summer. TAdding the fan dropped the temp by 10C).

You mean like Also DigiKey, Mouser,
https://www.aliexpress.us/item/3256803459080345.html if you want to take a chance

Yeah, that's the meanwell series - the "H" suffix will go high enough.
As you say, the ali offering looks good on paper, but the reality is always a gamble - a low power fan should hardly stress it.

one thing I’ve heard is that you should derate by 50% because only half the rectifier is in use,

De-rating is a good point, at least for a small load, it's easy to achieve.

Digikey has bit over 6000 possible matches

I'd looked at e14 (same group as mouser and digikey) and only the meanwell had come up. A PCB or open module would work, but a bit of a PIA to work with.

there is a company that makes DC (and AC) fans for greenhouses etc.

Nice fans, but too big (and pricey) for this job. One to keep in mind for suitable application

Here is a random PSU (5V 20A) I bought for a project before choosing a different approach.

 

[efficientPV]

That pictured inverter is not well suited for DC operation. It has a voltage doubler and will not work on DC unless switched to 220V due to the two input capacitors. Transformer ratio is designed to work with very high voltages well over 200V. As a simple rule, do not use a power supply rated over 180W and/or voltage switch because it will have voltage doubling on the input.

 

[PVorBust]

Good points - thanks.
This one is 5V 20A, so unsuitable for a variety of reasons (it just happened to be within reach).
Having a voltage doubler is a complication I don't need for this project.