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Forum Index : Electronics : 6Kw Ozinverter build
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renewableMark Guru  Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Does it make it much easier grinding the ends round? I was contemplating putting another layer of cloth tape or two to soften the edge a bit. Also what spools has everyone been using? Figured I'd get some dowel and mdf to make some up. Cheers Caveman Mark Off grid eastern Melb |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Well, there seems to be two schools of the art of re winding toroid cores. One uses small bobbin type spools (like you are planning) and wrap as much as possible wire on it. Of course, you are limited by the diameter of the available toroid hole (it gets smaller as you progress) and what length spool you can easily pass through. Pro: you can pull the wire very tight with this method. Con: you are limited how much wire fits on the spool, splicing wire mid turn is a nuisance IMO. You also further work harden the wire as you wind it tightly around the bobbin. Other method, use a large spool (hand fishing cast reel, cut to open), works well with single core. A still larger reel required for double stack, about bicycle rim size. This holds more than enough wire at a large diameter for winding a double stack. If this is used cleverly two in hand can be wound simultaneously, I did that successfully. Only con I can think of: harder to pull the wire tight unless a wire puller is handy. Suggest you get a cuppa or two and read all the posts on toroid rewinding. This may take some time but is, IMO, well worthwhile in the long run. Lastly, YES its *much* easier to pull wire tight around a rounded edge. Remember, the first idea coming into your mind is not always the easiest in the long run, your wire straightening method comes to mind  Klaus |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I ground the corners off with the angle grinder then used a flap sander thing in the drill to smooth it off and make it round.  If you don't round it then you have to get the wire to bend tightly on the sharp corners, a machine might wind it easily but doing it by hand it is easier with round corner and then there is less chance of short. 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 |
I pull the center core material out of the center to about 100mm diameter. This gives you plenty of room for the spools, and the big primary. The bike rim or fishing wheel is for folks with far more time and patience than me. You use a few more turns to compensate for the lighter core, but you win big time in what you can put into it. It is well worth it. My memory is poor, but I think 2800mmsq per turn per volt is good enough to work out your needed turns with the slightly smaller core.. the correct figures are on here somewhere.... or someone else will remember it anyway. I have wound over 16 of these things now, and would not do it any other way anymore. It is drop dead easy when you have plenty of hole to work with, and it is difficult if you have not enough hole to play with. I use Madness's idea of lots of 1.6mm wire or 2mm wire for the primary too. It is not real easy, but it save a lot of money, and seems to work better somehow.... maybe skin effect perhaps, but they do stay cooler. You will have a few joins using the spool, but it is well worth it for speed, and tightness. It is no big deal, just have some shrink tube and a hot iron handy. Using the spool method, you will find that hardening is not an issue anymore, as it actually works in your favor to put the wire where you want it... it goes naturally against the core, and if your hole has plenty of room it is a giggle. ..........oztules Village idiot...or... just another hack out of his depth |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Thanks fellas. OZ, Jesus Christ, over 16! no wonder you are mental now. Cheers Caveman Mark Off grid eastern Melb |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I started with the spool, tried other things and went back to the spool real quick. I used a spool from the real heavy resin core solder from the hardware store. They are tough as old boots and just the right size. As the hole got smaller I had to grind off a bit of the outer edges of the spool at about 45 degrees. Doesn't hurt to measure out your wire plus a bit extra and wind that on the spool, then put the offcuts aside for the primary which takes about 9 - 10 metres. I used a drill in the vice with a screwdriver in the chuck and a bit of tape on the handle to make it the right size so the spool would jam on it. Then in low gear with variable speed, one hand controlling the trigger and the other holding the wire with a rag to tension it. Your figures are the same Oz as they were previously maybe your memory is better than you remember! There is some discussion here about it from when I started. You must have got arms like Popeye after doing 16. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Had to work today, so not much progress. Just fibreglassed the two halves together. With all the different builds and the different progressions of the builds, it's a tad confusing deciding on a number of turns. Core thickness is 53mm, two high it's 140mm =7420 /2800=2.65 240/2.65=90 turns Now why does that sound wrong?  Cheers Caveman Mark Off grid eastern Melb |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I just plugged your numbers into the magic flux density calculator: https://www.electricaltechnology.org/2014/02/maximum-flux-density-bmax-calculator.html 240v .00005Mhz (50 Hz) 90 turns 74.2 cm ^2 (7,420mm ^2) And it says 1.61 Teslas which is getting pretty high. I would much prefer about 145 turns if they will fit. 240v .00005 Mhz 145 turns 74.2 cm ^2 Comes to 1.00 Tesla. Anything between about 100 and 145 turns will definitely work, but the more turns, the lower the flux density, and the lower the zero load inverter idling power is going to be. Cheers, Tony. |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Thanks mate, I have 4 3kw aero sharps to use so will build another one as either a spare, or split the house's load between them. So the first one I'll plan on doing it fairly simple and do three windings for the secondary. If it's kept to three what do you fellas recon about 145 turns fitting? OD is 206mm ID 100mm. Cheers Caveman Mark Off grid eastern Melb |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Its not super critical. Work out the circumference of your hole, and from the wire size figure out about how many turns you might be able to squeeze in there per layer. Wrap a piece of string around a couple of times and measure the length of wire per turn, and see how much wire you need, and how much you actually have. Then its fun time... Just keep winding until you either run out of wire, or complete one (or more) full layers. Whatever turns you end up with will work fine, the number of primary turns can then be juggled to get the required transformer ratio which only needs to be fairly close, not exact. Cheers, Tony. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
[quote]ID 100mm.[/quote] Thats about 314mm circumference. About 150 turns of 2mm wire would be just about right for one layer. So we might start with two spools and wind two in hand and fit maybe 75 turns on the first layer. Then we might be able to fit maybe 70 turns on the second layer. That would work out very well. If you can fit slightly more than 145 turns onto two full layers (as seems possible) do it ! If it ends up being a few turns less, it will still work perfectly well. Cheers, Tony. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Remember mine way back ? I was stressed out about getting the final turns in the hole ,it was chockers --- Anyhow professor Oz assured me that it would make no or little difference if they crossed over,-windings that is ..- She works perfectly -by the way I used 25mm earth (green) covered building wire ,,I,ll tell one thing , I swore it would be my last ,poor bloody 73 yo fingers were stuffed after a week of that!!!. plus the leather hammer and a few hundred swear words helped. Good luck ,watching every post . Bruce Bushboy |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I put 4 X 1.6 on the secondary with 98 turns, there was space to spare, I reckon I could have put 6 on and plan to do just that on the next one I build. Also I plan to try increasing the turns, I figured a 20% increase would be significant. Most people are running at 220 or 230 volts too which does reduce power lost in the toroid. Keeping it as neat as possible helps a lot as it takes up the least amount of space. Keep in mind every layer you put on will reduce the diametre of the inside hole. Even the first layer is reduced by the thickness of the wire so it will be 98mm. Dividing the circle into smaller sections would help to get your spacing correct also, I used a CAD program to make a paper winding template and put it under the Mylar before winding the first layer. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Thanks guys, Warpspeed, I'm using the recovered aerosharp wire 1.6 I believe. Being my first build reckon I'll tackle one layer at a time, two in hand may be a big ask. Remember guys I have only done small Jaycar kits, most of this is beyond me, I don't understand what most of the parts do, but I'll work it out(mostly with the help from you fellas) Like Tony Beets said how do you eat a whale? One bite at a time. Hopefully, the thread will be a reasonably detailed build from each step to completion, so some who may be wary of tackling something like this could be inspired to do so. Cheers Mark Cheers Caveman Mark Off grid eastern Melb |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
More parallel strands or using thicker wire, will definitely lower the temperature and make it more efficient at full flat out maximum power. Increasing the turns count reduces idling power by a LOT, and makes it much more efficient under light load. Its probably going to spend many hours at night with very little load, and thats going to eat up battery capacity if idling power is high. Unfortunately its not possible to increase both the wire thickness and the turns together without using up all the hole, and leaving no room for the primary. So there are some choices to be made between flat out sustained maximum power, and zero load idling losses. Whatever is most important to you should decide how you design your windings. There are no hard and fast rules, its a game of compromise. Cheers, Tony. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
We posted together. 1.6mm wire is 2mm squared, or about eight amps per strand continuous. Three strands would be about right, 24 amps = 5.5Kw I think I would wind this three in hand (easy with 1.6mm), that would be about 5mm wide per turn with the three strands laid on together side by side. Circumference 314mm should fit 60 turns easily onto the first layer. Possibly 55 turns on the second layer. And anther guess at 50 turns on the third layer. That is 165 possible turns. Its a lot but it does make up three full layers and its important to always have full layers. If you rum out of wire or wish to reduce the turns, spread out the top layer so it goes all the way around. Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Definitely one wire at a time, you will literally have your hands full with just one, you need to wind it as tight as you can. There is sufficient room for more wires and turns, winding it with a small spool as Oztules mentioned is the way to go. With the spool unwinding against the face of the core the wire is always trying to lay flat against the surface. Inside the hole is where this is most important, if the wire is just sitting a just a little away from the core it quickly uses up valuable space as you add layers. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Yes I like the way Oz did it, one layer/winding at a time seems much more manageable to me. If I keep it as close to Oz's build the less likely of issues to arise. Cheers Caveman Mark Off grid eastern Melb |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Am I right in thinking that the more turns the more heat buildup? Considering that I'm in Melbourne that probably won't be an issue, however, our summers can be nasty. Cheers Caveman Mark Off grid eastern Melb |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I could have saved myself many headaches by following that. Warps saying the extra turns will reduce transformer core loss(this is not the same as wire resistance), the energy losses turn into heat in the transformer. More turns will give a slight increase in resistance and at some point adding more turns would will just make more heat. Having said that I made mine using the same formula that you posted very recently. My Inverter is in a shipping container that gets hot, the toroid never gets hot enough to get the fans up to full speed except when I ran it at 8 KW for 30 minutes. Even then it did not get to 70 degrees, the materials in the toroid are good for better than 100. I have fitted an air conditioner to the shipping container, this was to save my batteries from a premature death which may be why the old ones completely failed late last year. Our previous summer was our hottest and dryest on record. The shipping container is a temporary solution until we move to new property soon. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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