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Forum Index : Electronics : 6Kw Ozinverter build
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Don't sweat it Mark, there is going to be a ton of room in that hole. This is going to be a very nice transformer, low flux density, low idling current, and just about the perfect balance of copper between primary and secondary. If you can fit 16 primary turns in there, do it. You may decide to remove a turn later on when you get into some serious testing. But its a lot easier to pull a turn than to add one turn at a much later stage. Cheers, Tony. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
All the wires will fit in around the circumference don't worry. I won't look like it at first when you wind it on but it will as you work with it. You can use the choke you have already. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
16 turns is too many, it needs to have a 9:1 ratio. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
It depends on if you are aiming for 240v or 230v and the lowest battery voltage that is anticipated. Nine to one works out to 128/9 = 14.2 turns, but 15 may be better. If 16 slips in easily I would still try that first, then reduce it to 15 later if necessary. 230v x 15/128 = 26.95 primary volts rms. Peak primary voltage will be 26.95 x 1.414 = 38.11 volts inverter dc required. That is probably about right for a lead acid battery down to about 40 volts minimum. If its going to be 16 lithium cells they will never get that low in voltage. Even way down to 2.8 volts per cell there is still 44.8 volts there. 230v x 16/128 = 28.75v rms. Peak primary voltage 28.75 x 1.414 = 40.66v volts inverter dc. Its going to do that easily with 16 turns. Putting on too few primary turns is not a good idea, it raises the primary current and increases the losses everywhere. Remember resistive losses rise square law with current. Going from 16 turns to 15 turns increases the primary current 16/15 = 6.7% But it increases the heating in the mosfets and primary by 13.8% Dropping from 16 turns to 14 turns increases current 14.2% and the heating by 30.6% Those are not insignificant numbers. Put on as many turns as possible until it only just reaches the required minimum mains voltage at lowest battery voltage. Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
If your FLA battery is at 40 volts there is something very seriously wrong and that is what Mark is going to be using. 9:1 is what is working for everyone else I am sure for Mark sake he is better to follow what is proven. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
So what is the end point voltage of your 48v lead acid battery ? Cheers, Tony. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
You do realize that I am a retired power electronics engineer and that I used to design commercial UPS and inverters for various Australian Companies that include Invertech, Solar Basic and Saft Nife. I was also battery applications engineer at Saft Nife for a number of years. And I had my own company for a while, Australian Power Systems where I designed transformers and other magnetics professionally. But then, what would I know........ Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
45.6 Volts is 0% SOC, 46.56 volts @ 20 SOC manufacturer of the battery says 20 SOC is the absolute maximum drawdown. Warp I know you have a lot of industry experience with transformers, power supplies etc. The 9:1 ratio works, what none of us know is exactly what goes on inside the EG8010 chip that makes our inverters work. 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 for the feedback guys. What I plan to do is not to stray too far from Oz's well proven design. There may be many other ways to tweak the design, however ATM I would like a rock solid proven design that won't fail me when it's needed. Like I said previously I may get a bit more adventurous with the second one. I have all the bits to make another, all the componets, 2 NIB aeroshaps, so I will certainly do the second, even if it's not needed I want a backup to just flick some breakers and BAM back up and running again. Doesn't sound like these go POOf too often though, but lightning could always root it good and proper. Cheers Mark Cheers Caveman Mark Off grid eastern Melb |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Here is some of Oztules words I saved talking about the differences between the powerjacks and the EG8010 "The egs002 or eg8010 are different, as they have a much tighter dynamic range for their spwm.. so for the 240v /48v version of the 002 or 8010 it will be more like 9:1 ( 26v primary)" 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 |
Looking at clockmans diagram of how his should have fitted neatly and how it actually turned out I would assume no way in hell 16 would fit anyway. Cheers Caveman Mark Off grid eastern Melb |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I would not be surprised if that one could not have been done better, he says below there it fit on paper. If you look you will see the wires curve away from the inside face of the toroid, they need to stay right against it to fit the maximum in. That is where I have used wooden wedges and tyre levers to push it into the right position. Have you decided if you will use welding wire or have a go at the repurposed wire? There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Fine so we have say for example 43 volts dc under load at max draw down at the inverter, allowing for a few small unavoidable voltage drops around the system. So our inverter can generate a 43 volt peak sine wave, that is 30.4 volts rms. If we put that though a 9:1 step up transformer we get 273.6 volts, even with a dead flat battery. Anyone here running their house at 270 volts ??? Why do we need to have a transformer wound that will produce 270 volts ? A 7.5:1 transformer would be much more sensible (for that particular battery). That would produce 228 volts with a dead flat flat battery right at the point under voltage disconnect, and full regulated rated voltage (230-240v) over the normal battery operating voltage range. I am not going to say any more about this. You build it any way you want, its YOUR inverter. Cheers, Tony. |
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Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429 |
Mad, Mark. My 75mm/2 cable primary is solid stranded and a absolute bugger to get to stay still while bashing it with a wooden mallet, but once there it tends to stay where its put. While the flexible welding cable goes walkabout a fair bit and moves around on the toroid and is not easy to stay in position. The choke is wrapped with very flexible welding cable just for that short bit and joined to the primary cable with soldered joint lugs. I also use very flexible welding cable on the break outs at the actual heatsink fastenings and Power board connections as this stops the stress on those parts. Everything is possible, just give me time. 3 HughP's 3.7m Wind T's (14 years). 5kW PV on 3 Trackers, (10 yrs). 21kW PV AC coupled SH GTI's. OzInverter created Grid. 1300ah 48v. |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Well the 4th winding went on well, only just fit. It could possibly have slotted one or two more wires in the centre. IF from the start you anticipated this, you could really really pull super hard and make it really taught and compressed in the centre to gain maybe one or two more mm in ID which would make a big difference when getting to the 4th winding. Sorry to see you guys getting distressed about the primary winding, anyway when in doubt ask the designer (not to say that's always right, but a good starting point) Cheers Mark Time for a beer fellas. Cheers Caveman Mark Off grid eastern Melb |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
 Here is some inverter porn for the toroid pervert. Some sections are just on 80mm others 77mm. I'll do the volt phase test tomorrow and put on a test primary winding. Cheers Caveman Mark Off grid eastern Melb |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Found a good source for 70mm in Brisbane if anyone up there is looking for any here Best price in Melb from shops was 22 per M. This delivered all the way from Perth actually works out $60 cheaper than buying locally from a shop, and they wonder why we are turning to online. Oh jeezus F me sideways against a tree look here you can bloody get the same cable shipped from bloody limey land cheaper than good old drunken bazza locally will sell it to me, providing he isn't on smoko or having a pie or chatting up the tasty truck lady. Cheers Caveman Mark Off grid eastern Melb |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
I think that the some may not appreciate that under load, we shed some of our over head clearance, and if you want very good voltage regulation at high power, I think the 9:1 holds. It must be remembered that the dynamics of this chip are fairly skinny compared to say the power jack, so it is interesting to see just how tight the voltage drift is with this 8010 chip. My tests show that there is very tiny drift with almost any load. Talking to the bloke I installed the last system in today... (he had those blue danish inverters..... which he now sees as overpriced crap.. which is not really fair) his lights always flickered when he turned on any mildy heavy load... now he can dump on kilowatts, and no flickering noticed... so the overhead shows up in the operation, and manages to provide near perfect voltage stability. I have had one drop out on very low battery voltage, and even with the apparently excessive overwinding ratio, it still fell down from maxing out the wave pulse ( I think thats what got it). It was very very very low, but would have happened sooner if the ratio was lower..... better for the battery perhaps. So I still think 26 or 27v is about right for a 48v system. Mark, it is your inverter so you can weigh up the arguments. Warp is correct in my view, if the chip had better dynamics, but when I replace the power jack boards with these in a true power jack inverter, I need to strip off a few turns from the primary, or it will not even get up to 240v. .......oztules Village idiot...or... just another hack out of his depth |
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| Mulver Senior Member  Joined: 27/02/2017 Location: AustraliaPosts: 160 |
I'm loving this Mark! Toroid love holes! Passionate Transformer talk! It's warming me back up to get stuck into my toroid  Keep up the good work!  |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Mark you might want to give the twisted wire a go, it is only going to cost you a little time, if you don't like it then buy the welding wire. They don't miss you on the price of it down there, you might get it cheaper if you offer 2 or 3 cartons of XXXX. Bloody hot here tonight, had to put a fan on my modem to stop it erroring due to overheating. Must be time for a new one. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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