 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Electronics : OzInverter OzCntrl PCB rev12 Sept2017
  Page 9 of 13   |
|||||
| Author | Message | ||||
Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Hi, if you bought that tape on ebay do you have a link for it? Sounds like something I could use. Thanks. Klaus |
||||
| brac321 Regular Member  Joined: 30/11/2016 Location: SloveniaPosts: 54 |
Klaus, it was purchase years ago from a company that makes larger power supply devices and goes bankruptcy ... How large / what dimensions of insulation do you need? My "roll" of this tape is 11cm high (wide). OffGrid 24/7: 250w black mono solar panels 6.4kWp, 1x Midnite Classic 150, 1x MorningStar MPPT 60, battery bank 840 Ah @ 48v, modified LF-8K inverter, DC/DC, hot water harvesting, etc. |
||||
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I use insulation paper from the motor rewinders and glued it to the heatsink, it is very strong and about 0.5mm thick. It will never break down at the voltages we are dealing with and easy to get. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
There are rolls of polyester film (Mylar) on e-bay that might be pretty suitable. The thicker five thou (0.127mm) stuff is quite tough and has excellent electrical properties and withstands quite a bit of heat. Comes in rolls and sheets from various suppliers. http://www.ebay.com.au/itm/Stencil-Film-5-sheets-A3-Mylar-127-micron-for-Airbrushing-Painting-and-Craft-/232511498935?ha sh=item3622c3eab7:g:jdgAAOSw3ydVmHQu Cheers, Tony. |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Thanks guys. I do have this tape link and it works well. But its adhesive and I wondered if there is a non adhesive tape that's suitable for insulating things that might get hot on ebay somewhere. the material motor winders use would be nice but I doubt its available in small quantities. Klaus |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I go a piece from the rewinders a while ago from the rewinders to use to rewind a Lister generator. It comes in a 1 metre roll, they cut half a metre off and it cost me maybe $15. I used about 5% for the rewind job so have had it lying around. I have dealt with a few rewinders and they have all been happy to help. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| brac321 Regular Member Joined: 30/11/2016 Location: SloveniaPosts: 54 |
Clockman, solder mask (paint) on your boards is of good quality and hard to scrape off. Was surprised that board is not galvanized completely but only where the solder mask is missing. Because solder mask is hard to get off I took another move and scratched only some additional joints in the middle of PCB for copper sheets. Then solder it with hot air station behind each FET and on those joints. These sheets shall provide useful contacts to both heat sinks. Board is populated with all FET's and for now operates well. I have feeling that signal on CRO is kind of modulated. It's clearly visible on analog CRO if I shorten (remove) my choke. Lower part of sinus perhaps bit more than upper part. Have not connected output filters jet, but hope they will smooth it a bit.    OffGrid 24/7: 250w black mono solar panels 6.4kWp, 1x Midnite Classic 150, 1x MorningStar MPPT 60, battery bank 840 Ah @ 48v, modified LF-8K inverter, DC/DC, hot water harvesting, etc. |
||||
Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429 |
Brac321, Honestly the boards are good to go as they are. Modifying the Primary heatsinks mounting may cause other issues, and boy those bits of shim are very close to the Battery cable - connections, a wandering insect and ZAP!!!!. We are dealing with serious amps here, and the board was laid out so that moisture, insects, dust, etc issues would be limited. I also note some of your caps and de-coupling caps are physically small in size, we deliberately overrated the voltages a bit. If you are sure that you know what you are doing,? then that's great! but be warned these power boards are deliberately designed as they are. Nothing with these PCB's and the OzInverter are industry standards, but if you stick to what we know that works then all should be fine. 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. |
||||
| Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429 |
I also note that the 2uf Capacitor on the AC that you have on your control board is physically small in size. It should be a ...... BB61 Polypropylene Film Motor Start Run capacitor 2uf 50/60Hz 450V AC, ...... or some thing similar. 'Oztules' found that some modern domestic AC appliances are Neutral grounded and this caused problems when the OzInverter was actually installed. I now note that 'Oztules' has now doubled up this capacitor, and I have added extra space on the New OzControl Board 12. 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. |
||||
| brac321 Regular Member Joined: 30/11/2016 Location: SloveniaPosts: 54 |
Cap. is sized 22x10x18 mm it is 2u2/450v, plus another one on trany. We can not use any Neutral grounded appliances here - both lines are separated because of grid protection system. My heat sinks are so heavy  , I need to mill some kind of support plates below the PCB.OffGrid 24/7: 250w black mono solar panels 6.4kWp, 1x Midnite Classic 150, 1x MorningStar MPPT 60, battery bank 840 Ah @ 48v, modified LF-8K inverter, DC/DC, hot water harvesting, etc. |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Hi Brac, I wonder why you bother with that copper foil. It does not help unless for some reason you put insulating washers under the mosfets. The metal surface on the mosfet conducts the high current to the heat sink, it is at the same potential as the middle pin (drain). So, the aluminium heat sink is the big current conductor with this design, three of the 4 power wires terminate on the heat sinks. Only the common (ground) high power wire is connected on the PCB. That should be rather wide and have very big tracks to each source leg. I am not familiar with the way this is done on the OZ board design. And, unless you tin that copper foil the shiny red surface will over time cover with high resistance oxide. If you want to see how I did it differently check the latest pictures in my post 'building an inverter from scratch'. If compactness is not a problem then I suggest you look at the way I located the large capacitors. For some strange reason many copied the original Chinese board layout which puts the caps in a heat tunnel between the heatsink fins. About the worst place for them to be from a long life perspective. And, putting them on the other side of the PCB, you can leave all heatsink fins large, no need to trim some short. The cooler you can run this inverter the better. Of course, that is if you plan to design your own PCB. With your bought OZinverter boards it may be best to put it together as it was designed. I see little reason to 'improve' it, it works fine. Then, when you got it working satisfactory, and the inverter building bug has you still in its grasp, you could start designing your own boards and let the fun begin... BTW, PCB's have the tracks 'tinned' (with solder), not galvanised, which is used on steel to prevent it rusting  . Klaus |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Tinker English is not his first language. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I know mad, neither is English my first language. It is, however, how I continue to improve it, by having pointed out small misunderstandings. I'm sure you can find a few oopses in my posts Klaus |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
English is my first language and I still have oopses  There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| brac321 Regular Member Joined: 30/11/2016 Location: SloveniaPosts: 54 |
Klaus, thanks for explanation and sorry for my English. I have real problems to express my self properly. Of course I mean tinned... and they are not. It would be better if they were, but I know not every PCB manufacturer do it that way. About small heat sinks I see situation a bit differently. Yes they are good current conductor regardless Aluminium for the 6 FETs mounted on them, but the middle pin (Drain) goes to the other side of the board on to Source pins of other 6 FETs. That current will in case of insulation on PCB flow only trough tiny middle pins. On the other hand, the large heat sink is on its copper (bottom) plane with few screws that helps sharing current. I see here asymmetrical operation inside the bridge under high loads. Therefor my experiment with copper foil. I'm real sorry if I "upset" some on the forum, it was only my thinking how to balance current flow ... I din't mean anything bad. OffGrid 24/7: 250w black mono solar panels 6.4kWp, 1x Midnite Classic 150, 1x MorningStar MPPT 60, battery bank 840 Ah @ 48v, modified LF-8K inverter, DC/DC, hot water harvesting, etc. |
||||
| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
You might like to think about ordering your next set of boards with 2mm fiberglass. Going up from 1.6mm to 2mm thickness does not sound like a lot, but its a great deal stiffer especially for larger boards. Another possibility would be to add some plastic feet under each heatsink. That would carry most of the weight directly. The screws that bolt the board to the heatsink could be made longer to pass through some plastic feet. The screw heads are often deeply recessed into the feet, so shorts through the feet are not a problem. Nylon screws and nuts and washers can sometimes be very useful for bolting things together that need to be insulated from each other. Another very useful material for assembling physically large or heavy electronics is fiberglass angle. This is sometimes called "pultruded angle" its not always easy to find, but it is available if you search. Just one example of what I am talking about: http://www.libertypultrusions.com/pultrusion-products/angles/ Large electrical wholesalers that supply electrical contractors and electricians often stock a limited range of pultruded angle. Its expensive in the larger sizes and more unusual shapes, but the very common 25mm x 25mm x 3mm angle is not that expensive. Its very easy to cut and drill and great stuff to work with. Its also surprisingly light and stiff and strong. Bolting a couple of pieces of fiberglass flat or angle between the heatsinks to tie everything together would really stiffen it all up. Cheers, Tony. |
||||
| brac321 Regular Member Joined: 30/11/2016 Location: SloveniaPosts: 54 |
Yes Tony, I will probably do some kind of prolonged feet in the middle and at the ends of board. Teflon or some other heat resistant material will be used. Have plenty of them at home, left over from microwave projects. Machinery is also there for turning, milling, CNC, etc. So no excuse not to do it  OffGrid 24/7: 250w black mono solar panels 6.4kWp, 1x Midnite Classic 150, 1x MorningStar MPPT 60, battery bank 840 Ah @ 48v, modified LF-8K inverter, DC/DC, hot water harvesting, etc. |
||||
| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I fit a sheet of 5mm plastic to the top of the heat sink with drilled and tapped m4 screw in the face of the heatsink. This makes it very rigid when assembled. There are only 10 types of people in the world: those who understand binary, and those who don't. |
||||
| brac321 Regular Member Joined: 30/11/2016 Location: SloveniaPosts: 54 |
Good idea Madness. OffGrid 24/7: 250w black mono solar panels 6.4kWp, 1x Midnite Classic 150, 1x MorningStar MPPT 60, battery bank 840 Ah @ 48v, modified LF-8K inverter, DC/DC, hot water harvesting, etc. |
||||
| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Hi brac, you are doing very well with your English. I was in your shoes many years ago, well before the internet, and found it hard to learn the technical words required in my job as an electronic technician. Anyway, about your board. It seems that it was not optimally laid out. But be assured it works for many inverter builders. I see what you mean by the high current having to traverse the small Mosfet pins at each side of the board. On my own PCB the drain current travels via the heat sink and 6 x 4mm screws (one for each Mosfet) to a very large 2oz copper PCB plane and thence to the other side of the PCB. From there it obviously has to go via the source pin to the relevant Mosfet but I made the tracks there very large. They easily coped with a 6KW load, spread over 24 Mosfets. I'm not sure if your foil addition is practical in the long run, remember that dissimilar metals in contact, like copper and alu, act like a tiny battery with the alu being eaten away. I would be wary using bare copper. Klaus |
||||
| Page 9 of 13 |
|||||
 Print this page |
