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Forum Index : Electronics : building an Inverter from scratch
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
What's the secondary voltage rating of that wee transformer you are using instead of the potential divider arrangement? 3v? Smoke makes things work. When the smoke gets out, it stops! |
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Clockmanfr Guru  Joined: 23/10/2015 Location: FrancePosts: 429 |
12v 1W or 3W. 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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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
OK, folks, I have ordered one of the 24v 3kVa boards from the link that Oz put up at the end of page one. Here is the link again for those of you who want a quick look. I chose the 24v version, as I need less then 3kW, and Madness is being very helpful indeed and helping me source a couple of Aero Sharp toroids. He's even gonna unwind the top winding we don't need, which is win-win, as he gets the winding wire, and I get a lighter toroid for shipping. 
As I don't need 6kW for a Tiny House, 3kW will be plenty I would expect, so a 24v system should suffice. This also allows me to use the Aero Sharp toroids pretty much as-is without having to strip/stack/rewind etc, as I think they are rated for 3kW as-wound. YoyCart are having 10% off at the moment, so I thought that now was the time to buy while I could get about ten bucks off the price. I will start my own thread when this board arrives, as I don't recall seeing anyone else build using one of these, so to keep different projects separate...... I have looked closely at the Oz inverter boards etc, but I have always been very attracted to things that don't need much work to make them go, so these pre-assembled inverter boards are perfect - for me. I will find out what MOSFET's they use, and order in spares of those and I already have some of the 002 driver boards, so that should keep me covered for my purposes. I will need some help from you inverter gurus though as to the guage of the wire for the primary winding, and how many turns for a 24v system, as everything so far has been based on 48v I think. YoyCart also say there are plenty of the 24v boards(17), but only three of the 48v ones, so I would like to know I can get more 24v ones later if my prototype works out well. Including EMS freight to New Zealand, a fully assembled board is US$100 - or about $140 in NZ money, landed here. Which for a fully assembled board, I think is rather good. All I should have to do, is wire up my toroid primary, connect it all up, and it should be up and running. I will be removing and bypassing the LM393 IC on the driver board as per other posts about that by Oz...... Smoke makes things work. When the smoke gets out, it stops! |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Please please use 48v for a house of any size at all. The 24v unit and 48v unit will be the same except for the simple ov/uv setting and maybe the fets.... but really the 002 board is any voltage you choose. There is not a single positive argument I can find to be using 24v. Your losses are much greater with 24v.... remember, the boards are essentially the same, but your I^2 R losses mean 4 times the losses for the same power. For the transformer, you will halve the resistance ( twice as thick winding)but double the current... so your twice worse off here too.... the squared current is the killer. If you look at the board, the current paths are not huge... and same problem... twice the current in the same architecture...125 amps for 3kw@24v... take a good look at the tracks, thats the rms current ... not the peaks...nearer to 200 plus amps for a 3kw load... how much for a decent compressor start surge. Now the same heat sinks will need to get rid of 4 times as much heat.... it is all bad. 24v units are toys... think this through for your sake. Off grid houses are more like caves with 24v systems. there are plenty here that are 24v... they live like peasants comparatively.... in very flash houses, but can't boil a decent kettel... and run the genny in ac coupling to do the washing etc. That unit cant AC couple to a genny.....so you cant rely on that as a way out either If I was allowed, I would use 72v or 96v, but that is a whole world of pain for regs. I think they will be a good little board... at 48v anyway. A serviceable unit at 24v for a utility shed... but if you have a wife, then 48v. Will help where we can, but reconsider your voltage.... I'll shut up now... but you know what I think and why. ...........oztules Village idiot...or... just another hack out of his depth |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
I will see if I can swap it for a 48v, but 48v is fine with me, so long as the board supports it. The MOSFET's on that board are HY4008W's, N-channel 80v/200A, so I expect they would be perfectly happy with a 48v supply. My guess is also that the filter caps will be 25v rating or something, but if that is all it really is, I could probably remove these myself and upgrade them to 63v versions without too much pain. I have emailed the seller, and we'll see what they say. As you point out though, I think that so long as the FETS can handle the higher voltage, then we could design for that, and there probably is not THAT much of a difference between the two different models. I am single - no wife or girlfriend to worry about needing lots of juice to run things, so all I need is light, computer, projector or TV and that would pretty much suffice. However, 48v makes sense - not entirely sure why I thought 24v was a good idea, but there you go!  Smoke makes things work. When the smoke gets out, it stops! |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Remember, 48v is really 60v min, and 24v is 30v min ( charge voltage for possible eq is even higher) So expect that the 24v unit has 63v caps, and the 48v unit should have 80v caps... I forgot the caps in the above argument... 
"However, 48v makes sense - not entirely sure why I thought 24v was a good idea, but there you go!" The world has many experts in the RE sales world... who are passionate RE people... and as such think that minimization is the goal, and sacrifice creature comfort to accommodate this. When a 200 watt panel was 2000 dollars, then this was completely understandable and fair go. Cheap solar has turned this on it's head, and now you can look forward to off grid being no different to on grid... but they seem to want to live in trees, and think using lots of power is a sin..... but it comes from the sun and is free. You buy 240v stuff, never 12v junk like they seem to advise... save a few watts for what??... and gas fridge... pure stupidity... over priced beer coolers if you have a day to wait for a cool beer. I have dual door ice making fridge, not some gas or 12v compressor thing, 700l freezers etc. Boil a jug, use a big microwave, vac the floor do the washing..... all at once... because now you can.... but not on 24v I want to live off grid, not just exist off grid. .............oztules Village idiot...or... just another hack out of his depth |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
"I want to live off grid, not just exist off grid." That and your "wife test" are the most profound statements I have ever heard regarding off grid power. Do you write books too John? Living off grid does not need to be a drawback, yet banks don't like giving finance if you are off grid unless you have a whooping deposit. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
UPDATE: They said they will send me the 48v 4.5kW version instead of the 24v 3kW version. Hopefully that is what will arrive.  Smoke makes things work. When the smoke gets out, it stops! |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Well done Grogster. For encouragement, here I am testing the response of the heat sink to no fans and the flat style power board both me and Mad are using. I am running the whole house, and the HW is on, the washing machine is on, as is the water pump, tv, and countless other gadgets at the moment.... and then the kettel. So this shows the usage while the jug is on. The tranny is a quick test thing well under rated, but still holding the 5kw fine... 
and this shows the mess making it: 
The transformer stabilised at 70C after 2 hours of average 2.5kw, with excursions up to 5.3kw. This is a test transformer only! Heat sink temp which is what we are really interested in here slowly climbed from 20c to 37c... and stabilised there. No attempt to cool, or even give it convective cooling opportunity. It is using an inspire heat sink... and thats it. The fets are sandwiched to the heat sink under the power board ( from clockman thank you). It looks like you may need no extra cooling if you use an average load of 2.5kw and mount it sensibly.... no houses use this sort of power that I am familiar with... normally 500w-600w max average over 24hr period... about 14kwh/day 48v gives you flexability, as the currents are not killer material. My place uses this sort of power for the 3hrs used for the HW to heat.... and I may mitigate this with some caps to pull the peaks down, and the time longer. ...........oztules Village idiot...or... just another hack out of his depth |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
Where did you get the 4x4 red LED displays from? Smoke makes things work. When the smoke gets out, it stops! |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
http://www.ebay.com.au/itm/NEW-AC-80-260V-100A-Digital-Ammeter-Voltmeter-watt-power-meter-volt-amp-110-220V-/15146405165 0?hash=item2343f603c2:g:7WAAAOSwZd1VXT5y .........oztules Village idiot...or... just another hack out of his depth |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
UPDATE: They are out of stock of the 48v one that Oz linked to, but the same manufacturer has more modern ones at 48v available - about ten bucks more, but that is OK with me, with current stock levels of 826 units..... Here is a link to the new YoyCart boards if anyone is interested in seeing the newer board. It looks pretty much the same to me, but this one is a different listing and comes in 24v, 36v, 48v and 60v flavours. Needless to say at this point, that I will be getting the 48v one!!!! Smoke makes things work. When the smoke gets out, it stops! |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Looks the goods... don't know how you managed to get it organised... well done. ( I don't do Chinese very well at all...) The only problems I see with those boards are less current in the fet specs, but more importantly ( and another reason not to use 24v), is there is only 10000uf of caps there to handle the ripple... they may get quite warm under high power... eg the Clockman board has 60,000uf capacity.... and still warms up under higher loads. It should work well, but cap life may...and I say may be limited by this ripple. It will depend on your usage, but whatever you use, it would be twice as bad in the 24v mode. You still need the inductor, and they are recommending 40uh.... should have good idle currents. Will follow your journey. ...........oztules Village idiot...or... just another hack out of his depth |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
That is encouraging Oz, I am planning to try the Aero Sharp in it's original configuration. Do the caps heat up much on that board? With that heat sink where you have it it is really far from ideal so sitting on top of the box it will be much better. That plus big tranny may just need passive cooling 99% of the time??? One thought I had was to drill holes through the heat sink where it is not covered by the the PCB so air could convect through it and also help cool in the box. I have got 12 heat sinks now so I hot nothing to loose. One of the Aero Sharps I got appears to be brand spanking new Last of my bits have been shipped, last item sent was the EG8010, Murphy's law it was the first ordered. Although O`Shannessey's law over rides Murphy (O'Shannessey says Murphy is an optimist) So plenty of time to sort out the tranny and get boards made. 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 |
Yes, I was pleased with the test... If you rotate the box to portrait from landscaoe orientation, there will be good convective cooling, and fans will probably never be required on any normal house duty... ie if 3 hrs didn't bother it at at least 2.6kw continuous.... then we are pretty safe when we put the thing vertical I think. Cooling holes in the top and bottom made from fan grills for the 120mm units should cool the transformer easily. What could be the problem with your plan, is getting the transformer in there without interfering with the tops of the caps.... At the 2-3kw levels, the caps did not heat appreciably or noticeably, they are big and there are 6 on this board. I suspect we may not need the fans at all down here, maybe up there on a 40c day, your possible for 70c. When the HW turned off , the heat sink ( after a long time) came back to 25c or about 5c above ambient at the time, and later towards the end of the day it came back to 22c and loads came back to 200-400watts, with a few more big excursions. ..............oztules Village idiot...or... just another hack out of his depth |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
@ Oz - I could swap the 1000uF 63's for some bigger ones like 4700uF 63's etc, provided I can get them in a small enough footprint and package to fit in there. What do you think? The key to dealing with Chinese sellers is learning to think and talk in broken-English on purpose. If you do that, they always seem to understand it fine! Certinaly not as bad as the "All your base are belong to us" sort of 'Engrish', but if you remain very specific and breif in what you want, it always seems to work - for me.Smoke makes things work. When the smoke gets out, it stops! |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Just checked it, I will have 10 - 15 mm clearance, this is by moving the transformer a bit further down into the bottom right corner (landscape) and mounting the PCB to the far top right. Mind you if the PCB has to come out the tranny will have to come out first to undo the heat sink screws. The PCB will need to be mounted on the heat sink then dropped in from the outside where the heat sink mounts. Another option would be to put spacers under the heatsink and move it out a little to create more space. Could do that as a way to get air circulation also by using say 10 mm long tube over each screw. 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 |
These are what I have on order. http://www.aliexpress.com/item/Free-shipping-Hard-foot-aluminum-electrolytic-capacitor-100V-10000UF-10000UF-100V-Volume- 35X50-10pcs/32587522808.html?spm=2114.13010608.0.63.yuZ0ol Chinese understand money very well, until you try to get some from them. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
@ Oz - the 4x4 LED power meter you linked to let me look at a heap of other ones on the market. I particularly like the DIN-rail ones such as this one here as I could then mount this on the same rail(s) as the rest of the system output MCB's and RCD's. Has anyone used one of those kinds of meter? Smoke makes things work. When the smoke gets out, it stops! |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Hi Grogster, I have one of the meters the same as OZ, before I began this project, mounting it was a pain as I had no where to put it so the DIN version would have been much easier. However now I am building my own inverter it will be going into the inverter front which will be very easy to do. Think about where it would be more convenient for you to read it. No doubt you want to see what your new DIY inverter is up to. After I get my inverter finished I will be working on a Arduino based monitoring system with data logging and network access so I can read what is going on via a computer. My charge contollers do this and I like it a lot as I can see at a glance what has been happening at any time. 
White in bottom graph is state of charge Brown battery current yellow battery volts green battery temp There are only 10 types of people in the world: those who understand binary, and those who don't. |
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