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Forum Index : Electronics : EI Transformer variouse types
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Before you start, you need get your hands on a suitable magnetic core, the bigger the better. If you can find two that use similar sized E and I laminations, so much the better. That will give you more material to work with. Some of the laminations will definitely get damaged when you pull these transformers apart, and will not be reusable. Having two transformers to dismantle will give you more material to make a single fatter core without having to re use bent and buckled laminations. Once you have all your laminations, that will give you some important dimensions on which to work out what to do next. If you are lucky there may be a very nice 220 volt primary winding that you can re use. All this is the first thing to do. Find some suitable parts to work with. Then its a case of rewinding using whatever material you have. The transformer ratio depends on the dc input voltage range, particularly the minimum voltage the inverter will ever see. That usually depends on the type of battery and the number of cells. If for example you plan to use four twelve volt lead acid batteries in series, the absolute minimum voltage might be about 40 volts for a 48 volt battery. It should never get that low, but there will be voltage drops everywhere. So a 40 volt minimum might be pretty realistic. As this will be a sine wave inverter the PEAK primary voltage can never be more than 40 volts (in this example). So the rms primary voltage would be 40v x .7071 or about 28 to 29 volts might be about right. If your required secondary voltage is 220, then that gives you your turns ratio, perhaps around 7.5 to 7.8 to one. If you have an existing primary, but have no idea how many turns it has, that does not matter. Just assemble just the primary on the core and connect it to 220v and wind on enough turns of suitable thin wire to reach between 28 and 29 volts. That will tell you the required number of primary turns for your inverter. And also the turns per volt, from which flux density can be calculated. If you plan to re use an existing primary, the turns per volt and flux density will be already determined, and you have no choice. Its then a case of finding the thickest wire that will fit into the available space on the core. Its usually easiest to run several strands of thinner wire in parallel, especially if using recovered wire. Work out what will fit, and squeeze in as much copper as you possibly can. Cheers, Tony. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
You can build an Inverter with 2 smaller transformers also, so if you find 2 identical cores that together give you sufficient capacity then this will work just as well. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
If it were mine, and I had a bloke that would supply the laminates, and muscle, I would approach it like this. If you get the square root of the power in VA ( 5000 watts ), it comes out to 70. That rule of thumb for 50hz will mean we will need a cross section area of 70cmsq for the size of the core. Now we know how thumping big it is, we now have another rough rule that says, 45/cross section = v/turn... or 70/45 or 1.5v/turn. For 48v on the 8010 technology, we need a primary of 28v, secondary of 240v of 160 turns for the secondary, and 18 turns for the primary. I would go for 8mmsq for the secondary, and 50mm for the primary.... if you can get it to fit. This is brutal rule of thumb, but should work slightly conservatively. It also depends on quality of laminate, but should cover most laminates you come across. I think a 3kw unit will be probably enough for that controller...( has only 3 hy4008), with correspondingly smaller core and wire sizes. For starters, to test your inverter, use a normal 28:240v transformer, and from this you will get some experience first. ( for 48v systems) You have several answers, hopefully one of them is what you were looking for. ........oztules Try this site. http://sound.whsites.net/xfmr.htm Village idiot...or... just another hack out of his depth |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I have just sent off an e-mail to AWM cores in South Australia for a quote on a pair of brand new suitably large C cores and bobbins. Let's see what the man says. Cheers, Tony. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Hi Azhaque That is everywhere in every industry Im afraid, not just Pakistan. Having the knowledge and experience to custom design is the rarest of rare skills. 95% of companies just reverse engineer their old products and tweak them without knowing the how or why. I'm confused, no wait... maybe I'm not... |
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| azhaque Senior Member  Joined: 21/02/2017 Location: PakistanPosts: 117 |
Thank you gents, all from down under. Great advice from the Gurus. Will start off on and re visit the transfo shop with the above info. Yahoo2. "95% of companies just reverse engineer their old products and tweak them without knowing the how or why.' I know what you are saying but that is for another reason, I think. Here our normal technical training system is based on a bastardized version of the old Guild system rather than a formal classroom based route. This means that to become a 'Master', one has to spend thousands of hours starting at the age of around 13, going to about 40. Of course it is just hands-on work with little or no theory. There is no licencing, no regulatory standards that are enforced, just the plain brutal stick wielded by the market. Thanks again. Much appreciated. A.Haque |
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| azhaque Senior Member Joined: 21/02/2017 Location: PakistanPosts: 117 |
Incidentally here is the excel file by ludens.cl that I initially used. 2017-11-13_021339_transformers.zip A.Haque |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Best of luck with it. I said "45/cross section = v/turn." should be 45/cross section = turns/volt. The cross section/45 = volts/turn... hence the 70/45=1.5v/turn ..........oztules Village idiot...or... just another hack out of his depth |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I have here a 240v to 240v 20 amp (4.8Kw) rated mains isolation transformer that uses a pair of those AEM C cores. These cores should run all day at 5Kw and barely get warm in an inverter. AEM part number is C1903236, and is known as an 190/32/36 core. Cross sectional area is 50.8mm x 63.5mm or 27.9 cm squared. Window area is very large compared to a toroid at 190.5mm x 63.5mm Weight is 14.7Kg for both bare core halves. This isolation transformer uses 300 turns on both primary and secondary of 3mm wire with 60 turns per layer, and five layers each on primary and secondary. Secondary would be 7mm squared good for about 21 easy continuous amps (5Kw) That completely fills the window very nicely. 300 turns and 240 volts gives 1.25 turns per volt and 1.3 Teslas flux density. A 29v primary would require 36 turns, and flat rectangular copper 5mm wide is a standard width, and would make one very neat 29v layer. We would need to stack several 36 turn windings one on top of the other, all wired in parallel for the primary. Six layers would be easy and there should be room for more layers than that. Each winding of 5mm by 2.5mm rectangular copper would be 12.5mm squared, and six layers 75 mm squared total at least, possibly more if extra 36 turn layers fit, which they should. Flux density of 1.3 Teslas produces a magnetizing loss of about 1.9 watts per Kg from the AEM curve (by eyeball). 1.9 x 14.7Kg works out to 28 watts zero load loss. I measured the zero load input power of my isolation transformer as 29.1 watts, so the practice bears out the theory. Thats probably not too bad for a 5Kw+ transformer. That should make a pretty good continuous rated inverter transformer for 48 volts, and would handle much more power than that for short periods. Still have not heard back from AEM on cost. Core sets both much larger and smaller are available, but I picked that one because I already had a set here that I could reverse engineer and actually test. If I don't hear back from AEM, they can be contacted at: sales@aemcores.com.au They can supply a fiberglass bobbin onto which the windings can be wound directly in flat layers, without all the problems of winding through the hole in a toroid. Ah, just received a reply from AEM: [quote]Hi Tony, Thanks for your email. AEM ceased manufacture of traditional style C Cores around 10 years ago. We now manufacture a product called Unicore. I have attached a brochure for your information or you may choose to have a look at the different core type we can manufacture on our website www.aemcores.com.au We can manufacture a Duocore as a direct replacement of the C1903236, with banding and bobbins. With regards to magnetizing current, you will find that as annealed Duocore will have a much lower magnetizing current than a traditional C core. If you would like to order a sample, the cost would be as follows: AEM Part No: URDUO3-C1903236 HiB An Quantity: 1 Price: $135.00 each + GST AEM Part: B1903236C Quantity: 2 Price: $28.30 each + GST Pack & Freight: $60.00 + GST Lead-time: Approx 7 days from order Payment: Via EFT with order. If you require any further information or assistance please do not hesitate to contact me. Best Regards Mark Mark Cushen Business Development Manager[/quote] That works out to $289.34 delivered. A fair hit, but it will save a HUGE amount of heavy physical work, and the magnetizing current should be even lower than 29 watts, but not sure by how much. Something even larger, or a bit smaller may be more to your liking, but at least it gives us a rough initial idea of the costs. Cheers, Tony. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
.... I make the cross section about 33cm sq. Rule of thumb would make that 45/33=1.36t/v... so 240x1.36=327 turns. This is more than your 300, but I thought the 1.3t was a bit high too. So it looks like the rule of thumb is in fact conservative. 327 would get the tesla down, and so the idle current. $300 for that Duocore is pretty good. It stinks that the freight is so much. "They can supply a fiberglass bobbin onto which the windings can be wound directly in flat layers, without all the problems of winding through the hole in a toroid." After 17 of them...... you get used to it.  ........oztules Village idiot...or... just another hack out of his depth |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes I agree, 1.3 Teslas is getting too high for an inverter, but that is what this mains isolation transformer had. I just ran with that, to see how the numbers turned out. Using just one large bobbin on one side is less than ideal too. The final diameter of the last winding to go in is pretty enormous using up a lot of extra wire length, and adding unnecessary resistance. The leakage inductance doing it that way would be higher as well. A far better solution is to use two half sized bobbins, one on each limb of the transformer. The windings then go almost all the way around instead of being just on one side. Much better coupling between primary and secondary and less total wire length. That is why I asked for a quote for two half sized bobbins. I was less interested in detailed design at this stage than the dollar cost of the cores. One other observation. Toroids seem to have much larger cross sectional magnetic areas, but the smaller window (hole) restricts the amount of copper. These C cores look pretty skinny, but there is a huge window area allowing for more and thicker turns. When you work it all out and compare say, a 5Kw toroid design with a 5Kw C core design, the toroid will have much more iron in it, than the C core. That may be favorable for cost iron being cheaper than copper(which is why they do it that way). But for us it has one big disadvantage. Magnetizing power loss rises exponentially with flux density, but its measured in watts per Kg of core material. The more skinny C core can have a much lower no load power loss than a big fat toroid. So for us and our crazy home brew inverters, that is a big plus. Cheers, Tony. |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Thats some great information there, I had an idea this topic would be helpful for those of us that may not have access to the same type of transformer, and looking for other alternatives to build an inverter with. It appears I was a little off with my number of turns for the C cores I intend to use.  Warpspeed That isolation transformer you have is almost identical to the transformer I pulled from the old battery charger, I never noticed any heat from it after charging a battery bank , I was going to try the idle current using my energy meter, just to satisfy my curiosity, however the little energy meter decided to emit some WHITE SMOKE so that fixed it. These C cores sound like real winner for me and I would certainly be happy with idle current of 30 watts or so.  The AEM cores look good too, even for the price, if a person has appropriate wire on hand to use or can find a donor transformer with adequate wire, I think it would still be a cheep inverter build (if everything goes to plan) compared to buying a Brand name inverter with this much power. For me the next job is to get the transformer apart, Nothing has beaten me yet, except for putting things back together. I have a few choices of wire some 6x3mm rectangular aluminum, round copper and flat copper strap, don't know what size primary wire it has on it already but the 80v secondary is 15mm x2mm Will have to do something about bobbins and work out which wire I am going to use and what will fit best. I plan on running 230v as most things a rated for it these days, certainly better than the grid voltage we use to get here (will talk about that another time, caused many blow ups). Oztules I like that rule of thumb works well. If I can run up to 5kw on this C core that would be good enough for me at the moment I would be hitting it with some high surges especially with some large electric motors. Cheers Aaron Cheers Aaron Off The Grid |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
That particular C core has a window width of 190.5mm. When fitted with the AEM fiberglass bobbin, at a guess, that probably allows for a copper winding width of 180mm. Now I have been thinking about how to fit some turns onto that bobbin. We need about a 29 volt primary and a 240 volt secondary. We could arrange to have 30 volts per layer of wire. The primary would use one layer of say 45 turns of 4mm wide rectangular copper strip, that would give 1.5 turns per volt (30v/45t) and 1.02 Teslas. The width of that 4mm x 45 turns comes to exactly 180mm. If that is too tight, we can drop to 44 turns per layer and 1.04 Teslas. The secondary will require eight layers of the same copper strip (8 x 30v). The primary will also require eight layers, but all the layers will be in parallel so we have 30v but eight times the secondary current carrying capacity. Now 4mm wide strip comes in various thicknesses. If we were to use 4mm x 3mm rectangular strip that would be 12mm squared, good for a continuous 35 amps in the secondary (35A x 240v = 8.4Kw). And eight times that 280A in the primary. The whole thing requires 16 layers, each layer 3mm + some polyester insulation between the secondary layers, and between primary and secondary. The primary turns go directly over the previous primary layer and do not need insulation. The build up of copper would be 16 layers times 3mm = 48mm + insulation + the thickness of the bobbin. Our window is 63.5mm tall, so we should be able to squeeze 48mm of copper into that if the windings are placed very carefully and each layer hammered flat with a rubber hammer on one side. Its only tight in the middle where the two windings come together. The outside can bulge out quite a bit without becoming a problem. If we use two bobbins, which is recommended, we place eight layers on each. Four 30v primaries all in parallel, plus four secondaries in series (120v) We can reduce the primary from 45 turns to 44 turns which is 1.5 volts less, or 28.5v The rectangular strip is much more space efficient than round copper wire, so we can reach 8.4Kw continuous. With round wire, about 5Kw continuous would be about the best to hope for with that sized core. We are not limited to this particular core ! Plenty of alternative sizes to choose from. I just picked this particular size because I already had one. The old C core running at 1.3 Teslas has 28-29w idling power absolutely guaranteed. At 1.02 Teslas it is going to be dramatically lower. My loss curve (again by eyeball) says 0.9 watts per Kg, thats 13.3 watts for 14.7 Kg And these new "Duocore" magic cores with a distributed air gap and possibly higher permeability annealed material might be even less than that again, but how much better I have no idea. So if you are prepared to pay for the good stuff, a new core + new copper strip, its possible to build fairly painlessly an 8.5 Kw transformer with amazingly low idling power. I have a mate that owns a transformer winding business. In the past I have had an arrangement whereby I borrow a large drum of wire, and wind my own transformers myself at home. He weighs the drum before and after, and charges me for the weight of copper wire I used. That way there is zero wastage. You may be able to wangle some kind of arrangement like that yourself. Cheers, Tony. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Using that 4mm x 3mm rectangular strip certainly works out well, nice and neat, couldn't do any better than that. I think if I was to use a different width rectangular wire I would have to spread them evenly over the 180mm length depending on the size i could end up with a gap between each turn. The bobbin's on the C core I have, actually they are just 3mm thick fiberglass strips bound together with some tape and no ends so they must have had it on a mandrel with a shoulder washer when it was wound up, there is some clearance on the sides so the steel band can fit nicely to hold c core's together. Single core dual coil configuration looks like the best way (core type construction) Would we still use an Earth shield between the primary and secondary layers or just leave it out? A layer of transformer paper seems to work Ok. The whole thing altogether would have quite a bit of weight to it, but it is easy to mount this type of transformer, would make it stand vertical and simply clamp the top and bottom then bolt that into the cabinet or box. Cheers Aaron Cheers Aaron Off The Grid |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes the 4x3mm will be very flexible and easy to wind, and its also easy at the end where you go up to the next layer. The very wide strip, 12mm and wider, is truly awful stuff to work with. This transformer I have does not use a bobbin either. The fiberglass bobbins are expensive and its understandable that commercial transformers may use some special tooling on a purpose built coil winding machine. An experienced and well practiced expert can work without a bobbin, but its a far from easy task. For a home brew effort by a first time novice, I would strongly recommend buying a pair of bobbins. At least you can then be sure the core will slip easily inside the finished windings and also take up minimum window space. These bobbins come as a pack of flat pieces of fiberglass, precision CNC cut out of a very large sheet. There are tabs and slots, so the whole thing locks together into a very strong three dimensional rigid shape. An earth screen is a good idea, and much easier to do than with a toroidal core! But it does take up space, especially as it needs to be well insulated on both sides. I just put my transformer onto the bathroom scales, total 33Kg. So there is about 18Kg of copper in that monster. The rectangular copper wire will squeeze even more copper onto the core than that. So for costing purposes, probably reckon on 20Kg for copper. Final power capability is only limited by temperature rise. The more copper you can put into it, the lower the resistance, the less heat generated, and the more power capability it will have. The smaller the mass of the magnetic core, the less idling power it will have for any given flux density. So the trick it to fit as much copper into the available space with minimum voids between turns and between layers. Mounting the thing requires some ingenuity, but the exposed ends of the C cores can sit on blocks of wood, or rectangular steel tube. Another common method is to mount it vertically with one end clamped between two heavy sections of steel angle. Cheers, Tony. |
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| azhaque Senior Member Joined: 21/02/2017 Location: PakistanPosts: 117 |
Sorry for the late comeback Oz. Was travelling. Shouldn't "hence the 70/45=1.5v/turn" be: "hence the 70/45=1.5 TURNS/VOLT" Regards A.Haque |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
No . Easiest way to look at it is 45cmsq=1v/turn or 1 turn/volt.. whichever, as 45/45=1.... so a 100 volt winding will be 100 turns Now any cross section bigger than 45 *must* mean that your getting more than unity volts per turn. At 90cmsq, you are getting 2 volts per turn... ( not 2 turns per volt..that would be 200 turns) so now a 100v winding will be only 50 turns.... and the arithmetic will just follow that. So anything more than 45cmsq will be more than 1 volt per turn, anything less than 45cmsq will be less than 1 volt per turn.... or more turns per volt... take your pick. ...oztules Village idiot...or... just another hack out of his depth |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
Just thought I would check how much this one ways as is,(bathroom scales) 32kg total and the paper insulation is about 0.3mm thick. As I'm on a shoe string budget ATM I will have a look around the scrap yards and other places for some wire and see what other bits turn up, or build it with the wire I have, should work out good anyway. Its going to be my project over Christmas, or even before then, will be ordering some electronics parts shortly and will get that side of it going as well. I could have had another one of these transformers for free, just could not carry the thing that day, already loaded up, went to get it the next morning and someone had already knocked it off, just another one of my missed opportunities. Cheers Aaron Cheers Aaron Off The Grid |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
It sounds like we have the exact same sets of cores. Just out of curiosity, I requested a quote from a Chinese company for 22Kg of 4mm x 3mm wire. I thought I may do better than with the local suppliers. [quote]Inquiry : Could you please supply a quotation for 22Kg of 200 degree Polyamide imide rectangular copper 3mm x 4mm delivered to Melbourne Australia by lowest cost method. Regards, Tony From url : http://www.windingwire.net/products/enameled-copper-wire/flat-copper-wire.html[/quote] [quote]Hi Tony, Thanks for your kind inquiry. I am sure we could produce 200C rectangular copper wire, and MOQ is 500kg. 22 kg is really small to produce for production lifor copper.ne. normally, 150kg each spool. May i ask are you producer or repair? Kind regards,[/quote] [quote]Hello again Vicki, We are research and development here. Often required to wind a single transformer for experimental purposes that may or may not end up as a production item. Its sometimes very difficult to get our hands on one component, or very small quantities of a particular item , as I am sure you will appreciate. It was hoped that you already had some stock that we might steal a very little bit from. Later we may possibly require a quotation on a bulk order, and that is a very different situation. Kind regards, Tony.[/quote] [quote]> Hi Tony, > > Good news for you. > > Our another customer just arranged new order for 3*4 flat copper, could cut 30kg for you. >for copper. > You want sample by air? > [/quote] [quote]Hi Vicki, So sorry, I have just arranged with a local supplier that has some 3x4mm in stock very close to where we are located. Regards, Tony.[/quote] Pretty funny really, but also a bit frustrating if I were trying to do this for real. Cheers, Tony. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1026 |
I had a look at that mob, they did sell on aliexpress at some stage, in smaller quantities. The same thing with the aluminum wire, they want to sell 500kg reel, Whats your opinion on Enameled Square Aluminum Wire? I know its used in many transformers and motors already to save a few $$$ and its not as heavy. Some of the big EI chokes I have use full width aluminum strap, paper insulation no enamel, corrosion has not been a problem yet. I did get some large multi strand Aluminum wire (power transmission line) from a local auction. Also have some bare round copper wire. It is possible to roll it and coat it with enamel, but ATM I think that is a step to far. Cheers Aaron Cheers Aaron Off The Grid |
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