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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 12:55am 14 Dec 2016
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Some time ago I mentioned that the frequency of my test inverter seemed to be low, near enough 45Hz when measured on the grid of my oscilloscope with the time base in cal position.
Well, it cant be that bad and it isn't. The 8010 circuit runs at 49.99Hz when measured with my frequency meter. So the CRO cal SW needs re calibrating ( one day...)
But the funny thing is I did not know I always had a frequency meter. Its a function on my AC/DC clamp meter. I always used that clamp meter for measuring current and did not realise it can measure other things too Klaus
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 05:55am 14 Dec 2016
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Tinker, in unipolar modulation, spwmout3 and spmwout4 is the high frequency outputs, spwmout1 and spwmout2 are the fundamental wave form outputs..... lemme see... thats pins 29 and thirty on the 8010 are the spwm 20khz outputs with the sine wave information, leaving pins 27 and 28 to do the square wave fundamental part of the bridge operation.
In your nomenclature, thats 2ho and 2lo are the spwm outs....
So we turn on 1LO for a full 100th sec, while tickling the 2HO fet@ 20khz to get the shape we want for half a 50hz waveform.
Then we go turn on 1HI for 100th sec, and tickle the 2LO with 20khz to get the second half of the 50hz sine wave built.
==========
Now just to make sure there is no mix up, I used 4 fets per leg HY4008 for the 15kw surges, thats 16 total.... did it easily. The motor started with no sign of hesitation at all... nix.
==========
Warp, it is getting too complicated with boost converters as well.... I think it would be better to use an extra transformer for the 1:1 part ( that one would be 50v:230v), but change them all so we use 50v and step up (50v:76v7 and 50v:8v5 and 50:25v6.
The transformers are already required, may as well wind them to what we need, and we simplify the safety and battery requirements, and get some isolation between the batts and the output.
This would just mean, pick your output voltages and wind to suit... suddenly all simple again.
I know this means non-standard transformers, and you now need a decent one for the 50:230 part that was not required before .....but you only wind them once.
Would not mind giving this a go in that guise. Maybe just use microwave transformers for the mock up. bit lossy, but would work.... and can mix and match laminates to get the size we need for the heavy lifting parts. If the microwave laminates in their new combinations were not too lossy, would be a very cheap unit.
This also means fets again, but those chinese HY4008 units are easily big enough for you sized unit.... as singles, not bunched Slow switching with single ones were in the 2.5kw range on tests. 200a@2.9MO 80v TO247 for less than a dollar each. Mine tested at less than 2.9mo for all 24 of them. Tinker would have found the same I expect.
Unfortunately, the 8010 solution is dead simple, and near impossible to beat even at high power... but I like this concept for some obscure reason.
...........oztulesEdited by oztules 2016-12-15Village idiot...or... just another hack out of his depth
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:44am 14 Dec 2016
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Oz, I did build an inverter exactly that way about thirty years ago, still have it here somewhere. It was only an experimental baby though, 12v 500 watts.
It used three transformers exactly as you suggest, 12v primaries with push pull mosfets driving each transformer. The unique feature about it was that it could compensate for changes in battery voltage, providing a regulated 240v sine wave output with inputs ranging between about 10v and 16v (from memory).
Here is what remains of it after thirty years, the microcontroller board and a few other parts are missing. But basically it is thee push pull low frequency square wave inverters 40W, 120W, and 360W with the secondary windings connected in series.
It voltage regulated by switching between multiple lookup tables in EPROM to keep the output voltage constant. Obviously the height of each voltage step changes with battery voltage, the transformer ratios being fixed. But by changing the switching points, and the total number of steps, the output voltage of the inverter could be regulated withing close limits.
At low battery there were more but smaller steps. at high battery voltage the steps became slightly narrower and taller, but with fewer total steps. It used a 68HC05C8 microcontroller which has 8K EPROM.
Should still have all the documentation for that here too somewhere.
It worked very well, but as you say, required very special custom wound transformers. The main disadvantage (as always) with low dc input voltage inverters was the high input current, leading to the inevitable efficiency problem at full power.
Thirty years ago toroidal transformers were less common than today.
But there is no reason why three (or four) large toroidal low frequency square wave inverters could not be coupled up together in exactly the same way to make some very serious voltage regulated sinewave power.
All non critical low frequency switching, no high frequency PWM, and no output filtering required.Edited by Warpspeed 2016-12-15Cheers, Tony.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 10:58am 14 Dec 2016
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Oz is that inverter similar to the Trace with its 3 transformers?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
Posted: 11:16am 14 Dec 2016
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Don't know. Not familiar with a trace three.
All this is definitely not a new idea, people were building these long before microprocessors or high frequency PWM were invented.
Its worth thinking about, because a modern microcontroller can provide a means of providing excellent output voltage regulation which was just not possible in the old days. Cheers, Tony.
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 02:45pm 14 Dec 2016
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Certainly fits the facts as I know them Mad.
Fiendishly tidy unit for a prototype there Warp
.....oztulesEdited by oztules 2016-12-16Village idiot...or... just another hack out of his depth
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:57pm 14 Dec 2016
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It was hopefully a small prototype for future production, but it never went any further. No way we could compete with low cost imports. It was a really solid bullet proof little unit, but just too expensive to manufacture. Only 500 watts, but it would start up a full sized domestic refrigerator with ease.
It looks pretty sad now covered in thirty years worth of dust and grime.
Cheers, Tony.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 03:56pm 14 Dec 2016
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This is my new 3Kw inverter using five smaller toroids which fit easily into an old computer case.
Only have one power board for it right now, but otherwise apart from the missing circuit boards its pretty much complete.
Edited by Warpspeed 2016-12-16Cheers, Tony.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 11:57pm 16 Dec 2016
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So I was hoping to tickle out 2400W from my rewound 2.5KW toroid with the 4 x HY4008 test inverter.
Well, it handled the half power setting of my fan heater well enough but only lasted a few seconds on full power (2400W) when that happened:
I must say those HY4008 do a spectacular show when they go south.
My copper strip clamp connection method worked well, the bent over leg part on the copper side of the PCB looked fine. The Inside of the chip blew apart and a melt down of the source leg (wide part) occurred at that pictured place.
I was testing the sub heat sink idea BTW but never got it hot enough. Oztules, were your mosfets screwed directly to the heat sink or on silicon washers like mine when you did your 4 mosfet/2.5KW test?
There was a distinct flat part at the zero crossing on one side of the sine curve for the few seconds I could watch the trace but this was not as pronounced as those that Madness pictured in his thread.
I have to get this thing to reliably run 2.5KW on just 4 x HY4008 before I'm game to possibly sacrifice my 16 x HY4008 inverter.
The built continues... Edited by Tinker 2016-12-18Klaus
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 12:32am 17 Dec 2016
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The fets were directly bolted to the thick heat sinks from cut up aerosharp 1k5 inverters.
I did not run it for long like that as the fets on the spwm were getting fairly hot fairly fast ( 45-50c in only 50 seconds or so ).
That was with 4 fets total on the board..... later with 16 total, we ran the 5hp induction motor on the lathe.... measured start up was over 14kw with a clamp meter.... which if I could measure faster would be higher I expect. It should theoretically be peaking at 20kw or just under, but I have not measured that as yet. Don't know what the scan rate is for the meter.... would have to use the cro.
To run it at 2.5kw with four fetsfor a reasonable time, would be feasible I would think, but it would need to be matched properly... ie the windings to the voltage better than rule of thumb and a carefully designed inductor.... good layout, good cooling.
Spent a few hours playing with a few boards, tidied up the current control, back to using pin 6 for start, IFB for current with SCR and TFB for temp only.
Needs proper testing... then will modify the pcb properly, and get some more built.
Warp,
I looked inside the one I am building at the moment, and it looks so stupidly simple..... I look at yours, and see it is not a simple build. I will pour over the plans to see if I can fully understand the switching you worked out.... but will stop there I think.
.........oztules
Edited by oztules 2016-12-18Village idiot...or... just another hack out of his depth
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 01:31am 17 Dec 2016
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Tinker one reason I abandoned the way I started out mounting the MOSFETs was the need for electrical insulation. I know you want to do it your way however what won me over is the original Chinese design is so elegant in how it uses the heatsinks as conductors. So there is a double benefit, the conduction side and the better heat transfer due to the FET being bolted directly to the heatsink with no rain coat. (it is just so much better that way)Edited by Madness 2016-12-18There 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
Posted: 01:56am 17 Dec 2016
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Madness, the idea of placing a heat sink 'inside' a box and then using fans to shift the hot air outside is not the most efficient way of doing it in my book.
Yes, the Chinese hot (electrically) heatsink idea makes sense from a simplicity point of view but that's all, it mandates to place it inside a box though. Regarding the current conduction, my 37.5mm sq copper strip tracks beat all the 2oz PCB boards hands down.
I have a modified Powerjack inverter running my house now, this time of the year the 4 fans in it run virtually non stop. I'm trying to improve that with the outside heat sink idea.Klaus
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 11:36am 17 Dec 2016
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It looks complicated because there are four power boards and five transformers, but realize that those parts are identical repetition, but there is a fair bit of interwiring as each transformer has six wires coming out of it. So it looks a real tangle.
One idea I am pretty pleased with is each power board has four main connections going to it, +230 dc, -230 dc, neutral, and ac out. These terminate on a plain sheet of thin fiberglass from underneath onto four long 4mm screws. The four power circuit boards just drop onto these four long screws from the top.
This makes the four main electrical connections, and holds the power board in position. I can replace a power board by just removing four nuts and pulling out the plug at the end. No need to stuff around unsoldering individual wires.
Looking at the burn damage to the PCB in the above picture, it is exactly why I now use screw terminal blocks to connect all my TO247 packages onto the circuit board.
It completely eliminates the possibility of damage to the board, and its much quicker to just loosen three screws than to unsolder three mosfet legs.
These screw terminal blocks will easily carry any current the legs of a mosfet or IGBT can carry. This is what I would be using for vertically mounted TO247 package mosfets.
Cheers, Tony.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 11:38am 17 Dec 2016
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I have made 1mm thick copper overlay to go to the PCB which I am yet to try. This would give me effectively 140 SQ mm across each bridge and 280 SQ mm for + & -. But with 2 OZ PCB I have run for 30 minutes at 8KW, I don't know what temperature the PCB was, soon I will have a data logger built which will include a temperature sensor on the PCB. There has been no noticeable damage to the PCB so far from this.
With the big heat sinks I am using the Inverter will run up to 4 KW continuously and it does not get over 45 degrees with no fans turning on. Natural convection keeps it cool as it is vertical in the case and has 140 mm fan holes top and bottom.
I am not critical of your method, it was your idea that inspired me to go the way I did initially. 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
Posted: 12:24pm 17 Dec 2016
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That is an excellent idea.
Having vaporised a few tracks myself, I now sometimes run very heavy single strand copper wire over some critical tracks BEFORE the board blows up, to carry any anticipated fault currents.
It will always burn at the weakest point, and that should hopefully be right at the silicon, not on the circuit board or interconnecting wiring. It is prospective fault current you need to think about, not normal maximum operating current.
Any suggestions made here, are not criticisms of how a thing is already being done, but just ideas that people may like to think about incorporating for a "next" project.
Heatsinks really need to be external and fully exposed with vertical fins.
But an internal heatsink that is fully shrouded with forced airflow very carefully ducted through it, can be made much smaller and be much more efficient, as long as you trust the fan.Cheers, Tony.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 12:37pm 17 Dec 2016
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I made the overlay by using the same toner transfer method and a laminator to transfer the toner onto the copper. The I cut most of the excess off then used a grinder to take off the rest and drilled the holes for MOSFETs and Capacitors. End result is it is identical in shape to the copper on the PCB.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
Posted: 12:52pm 17 Dec 2016
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I really like this idea !Cheers, Tony.
KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178
Posted: 02:19pm 17 Dec 2016
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OK so i read some banter in there regarding torroids in the "Australian Made" inverter.
Tinker - the couple you got from me weren't from LS series (off grid) inverters but rather from PVE1200 and PVE2500 inverters. SO disregard what is below if you found an LS one as your test torroid.
Each unit had quite specific input voltages ie the 1200 was 60-72V input unless in "battery mode" where it would pull some power from a fully charged battery for example when used as a grid tie with a wind turbine.
The 2500 was designed for double those voltages and yes both units will happily run without overheating at full power in their as -designed configuration.
All that said.....typical failure mode of these is the DC Circuit breaker on the front panel which is a very easy fix to simply bypass it as was never required in the first place!
I have a few in the garage that came from system upgrades, am curious if worth the trouble to build one / two into a working 24V off grid (albeit small) inverter. (although i did read OZ said running 2 torroids in parallel can be more pain than gain
Luck favours the well prepared
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 03:50pm 17 Dec 2016
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KarlJ
Two in parallel will be fine,....... the reason not to is that it is 25% less efficient from the copper loss perspective, than unwinding and rewinding again as a dual core unit. ( you lose 25% of the copper for the same turns in a duel core unit)
Apart from that it is essentially the same thing..... would go 48v not 24v if your going to use two.... easier to wire up.
The rest is dead simple as you have read by now.
...........oztulesVillage idiot...or... just another hack out of his depth
Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429
Posted: 11:48pm 17 Dec 2016
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Hmm...... not so sure about and mechanical pressure connection on components at this kind of power.
Working in the Micro mechanical World, if you look at that screw block connection and the pressure screw pushing the plated flat with a microscope, the metal surfaces resemble a Mountain range of peaks and troughs.
Yes plating fills some, but the problem is still there.
Heat is also a problem as the constant expansion and contraction on the mechanical connection leaves the connector to become loose over time, and then we are in trouble. Maybe get away with it with household connections etc, but with this kind of Inverter machine, we require 24hr 365 days a year constant operation, hot, cold, and all sorts of environment conditions. Remember the machine is pulling serious amounts of power. Poor contacts and its smoking time.
Me I like solder, it connects and spreads the load, but being solder the heat expansion and contraction is not much of an issue on the connection.
Me,... I hate mechanical electrical connections.
Just my two penny worth.
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.
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.
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