Hi guys, there’s been a few discussions around the traps on sourcing suitable toroids to rewind for inverters and I thought it may be handy to have an up to date conversation.

Certainly the cheapest entry (here in Australia) can be had by sourcing old Aerosharp grid tie inverters  …  though if you are wanting to build a decent output inverter, you must aim for a 3kVA Aerosharp. They also sold a 5kVA GTI apparently, but I’ve never seen one.

Sure, their 1.0 and 2kVA inverters each have a toroid  …  but they are babies compared to what we want  …  so don’t waste your time with them (unless you’re building a Warpverter). Keep an eye out for a model HR-INV-X01-030

HR-INV-X01-020 = 2kVA and HR-INV-X01-010 = 1.0kVA  …  and they all look very similar

I had great success when I first started looking by searching for solar repair companies. Then I rang them and asked the question. Very first one said yes, there’s some down the back  …  we get $25 each for them for scrap  …  you can have them for $25 each. I couldn’t get there quick enough.

After picking up a few I was after another and they had run out. So I rang the next repairer on my list  …  and they had one for $50. Still a bargain I thought, so I grabbed that too.

I keep “Aerosharp” in my search on marketplace and see them quite often  …  but usually they want stupid money for them and never get sold. Still a bargain there occasionally though.


I have no idea about the US but here in Adelaide South Australia we have AEM Cores who may well be the only supplier/winder of toroid cores in the southern hemisphere.

They can wind toroids from strip up to 105mm wide, to whatever size required.

If you want one higher than that, you need to stack two together  …  so for 140mm high, they would wind two 70mm ones and stack them  …  then anneal them in the one unit.

I’m waiting for a quote on a couple sizes but it hasn’t arrived yet. One is the same size as a 3kVA Aerosharp toroid and the other about 25% bigger. I’ll post details when the quote arrives.

Of course freight will be a significant amount due to the weight, though no major problem if you can collect it.

Maybe tinyt or others might be able to give us some clue on what’s available in the US or Europe.

Okay, now that is out of the way, there is something else to be aware of  …  there are actually two different physical sizes of toroid core found in 3kVA Aerosharps.

Both have a 98mm ID and are 70mm high  …  but one is 190mm OD and the other 210mm OD  …  don’t ask me why  …  and one has a blue label and the other a yellow label. So ideally you’d want two the same if you’re gonna stack two of them for higher power.

If I was needing more toroids, old Aerosharps would be my preferred choice. In my experience, they have been 50-100 times easier to find than an IFLA or forklift battery  …  so pretty easy really. If I had plenty of dough, I might spring for new cores  …  but I’d have trouble going down that track knowing you can get secondhand ones cheaply.

Another big advantage is all the hardware and goodies that come with the old inverter  …  along with kilos of 1.6mm copper wire which can be reused and save more $ again.

The large chokes and all the big caps in my four MPPTs came from wrecked Aerosharps.

The clear mylar tape that insulates the windings can also be reused and again saves heaps of $.

I haven't seen Aerosharps around locally for years,
https://www.tortech.com.au/
Shipping for one of the ready made toroids was reasonable, but a bit small for our purpose.
Might be worth checking with them as they will make one when you enter the details in the Transformer Custom Design sheet.
https://www.tortech.com.au/custom-design/
Perhaps they can supply a bare core, worth asking.

Thanks Aaron, I hadn't seen Tortech as a supplier.

I waste a lot of time on Marketplace and am surprised to still see Aerosharps quite often. I'm not in the market for one myself so haven't bothered to ask any questions or try and bargain them down  ...  but I'm in a group where there's a lot of discussion on building an ozinverter and there's a number looking for cores.

I tried ebay on this side of the pond but they want stupid money, I can get a whole working ali inverter for the money.

The bay are using interesting techniques, they email me competitive similar product for sale, then they offer 10% discount on the thing I looked at or free shipping and returns, now I'm getting requests to make an offer on the thing...

That's interesting davros, I haven't noticed that technique yet with ebay.

I certainly notice with aliexpress that if I'm looking for something specific, I really struggle to find any reference to the item at all  ...  and yet after a few days, every time I'm on the site I get all sorts of offers and see more and more options. Just have to be patient there.

Doesn't help with toroids though I'm afraid.