Why not just use a 12 volt computer type fan ?

Les.

The fan mentioned uses 13 watts power, which tells me that it is quite a bit more than a normal "computer fan" would be.
It is also an induction motor type, and so it might possibly need more than just a simple "H-bridge" to drive it effectively, given that a simple bridge will deliver a square wave. Certainly a scheme with a bit of "dead time" between alternating pulses of opposite polarity is possible, and theadding a suitable capacitor across the motor winding to resonate with the drive frequency.
So at this point an input from somebody who has driven a small induction motor with some sort of inverter is what is needed. And that is not me.

As for isolation and the panic about how the fan must be isolated, consider that 12 volts from a battery system is not a shock hazard. I quote: " I’ve converted all my home lighting circuits to 12V DC to take advantage of solar power I’m gradually installing. " So there is no need to think that this is a mains powered rectified DC system that poses such a POTENTIAL shock hazard.

 

Latest thinking from me: I’ve not found a low power inverter that’s suitable (it seems very inefficient to use a 250W inverter to power a 13W fan). So I’ve gone for the bespoke inverter design approach. I found a PWM MOSFET driver module which generates pure sine wave drive for the H bridge. I’ve bought a 30VA 230V/12V transformer and a set of IRF3205 power MOSFETs. There’s a good guide to using this driver module on YouTube (but with some interesting safety flipflops in the shot with the angle grinder!):

The module is detailed in the video but I bought it on ebay: https://www.ebay.co.uk/itm/27576864...pDdeQpdTZa&var=&widget_ver=artemis&media=COPY

 

I should have added that I’m not building the 1kVA version, just a low power inverter using the same driver module.

 

Edit: on further research I appear to need a 7V transformer rather than a 12V one. It’s difficult to find definitive information about the transformer secondary voltage. Anyone got any guidance? The PWM module will be running in bipolar mode.

 

If you are driving an H bridge fed with 12 volts with the EGS002 module you should get slightly less than 12 volts peak output. Lets say 11 volts peak which will give you 7 volts RMS. So you will need a transformer with a 7 volt primary and a 12 volt secondary.
I had not heard of the EGS002 module. It looks very usefull.

Les.

 

You will probably not ever find a seven volt transformer. And creating any inverter from 12 volts will get you 12 volts across the primary to drive your fan. so no need to seek a special transformer. Just be careful that the wires from the inverter to the fan do not get connected to anything else, nor grounded. The only challenge with this approach is in setting a frequency that the fan is happy with. A motor designed for 60 or 50 HZ may not be happy with 400 Hz .

 

Can you move the fan out of Zone 0 and Zone 1? If so you can use a 230V fan, and you are much more likely to find a transformer you can use. (And the fan supplier might take pity on you and swap your fan for a mains fan)

 

I’ve bought a 230V/7V transformer off eBay and will reverse it to connect to the transformer that came with the fan

 

Hello all. Im bumping this cause i am looking into building something similar as well

.

It is better for you, and less confusing for other forum members, if you start your own thread and include a link to this one for context.

ak

 

For a supply that is producing only 1 A, that is a *lot* of filter capacitance. Peak-to-peak ripple at the input to the regulators will be around 1.2 V. Is there a reason it has to be so low before regulation?

ak