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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 04:23pm 22 Sep 2017
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Finally worked out the resistors required for a 9V transformer.
The 7k5 changes to 4k3 and the 1k8 on the bottom side needs to change to 1k5, I can now adjust between 215 to 250VThere 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: 04:33pm 22 Sep 2017
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I am all for re using things I already have, so I can see where you are coming from.
But spending a few thousand on solar panels and batteries is really unavoidable, and a couple of hundred more (or however much it is) for a transformer core that is going to save a huge amount of work is not really a big deal.Cheers, Tony.
Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429
Posted: 09:22pm 22 Sep 2017
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Thanks Madness for that.
So now a 230vac to 9vac sense transformer for the OzControl Board, just in case the 230vac to 12vac transformers are not easy to obtain.
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.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 09:29pm 22 Sep 2017
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I doubt 12V trannies will get scarce, I bought the 9 volt ones because they were cheap.
Edited by Madness 2017-09-24There are only 10 types of people in the world: those who understand binary, and those who don't.
Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429
Posted: 10:09pm 22 Sep 2017
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Warpspeed, thank you that was an excellent description you jotted down.
When I update the OzInverter book, and with your permission and acknowledgement I will add your jottings.
As you say its finding that happy sweet spot.
I was gobsmacked that Oztules seems to have got the OzInverter toroid build with his empirical calculations pretty well spot on.
In the book I give all his cross sectional core calculations and copper winding ratios and count calculation's, so what ever size of core you have its possible to progress with a decent toroid. I also liked Oztules testing methods as you build/wind, to clarify that the toroid is on the right track. Again in the book. The fact that he also did it all out of used second hand parts was very enlightening.
His recommendation on coating of thinnish viscosity epoxy resin, on each secondary enamelled copper winding, before each mylar tape winding, really does keep things silent, and important for longevity, vibration/rubbing free. In fact the very quite buzzing from choke makes more noise than the toroid.
My smallest set of new cores 190mm OD, 90mm ID, 120mm thick cost me about $160. The largest set, 230mm OD, 100mm ID and 140mm thick cost me about $220.
Most of the time A Normal, but yea whats normal, domestic household is probably ticking over at say max 1kW, but then a couple of appliances get switched on say 3kW for max say 30 minutes, then those exceptional times when 6kW gets pulled. This is of course heavy on the battery bank.
However, I am using the OzInverter with mostly AC coupled GTI's, so trying to use the battery bank as little as possible within daylight hours, with the GTI's putting in to the OzInverter Mini Grid.
The household and my other buildings are directly using up the GTI's output.
Now if the batteries are low the GTI's back charge through the OzInverter, and I use the push back by the batteries that raises the 230ac voltage slightly, to shut down the GTI's, so the back charging is not to excessive for the batteries. Importantly this method also means that I do not need such an excessively large battery bank.
Warpspeed do you see any problems with the OzInverter toroid when fluctuating back charging on and off all day.?
Edited by Clockmanfr 2017-09-24Everything 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
Posted: 10:31pm 22 Sep 2017
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Thanks Madness trim pots for absorb and float voltages and trim pots for setting absorb time is probably a simpler method for setting up, especially for all sorts of different folk around the World. Edited by Clockmanfr 2017-09-24Everything 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.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 01:21am 23 Sep 2017
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I believe anything written on an internet Forum comes into the public domain. Pick out whatever bits and pieces you feel may be helpful, and no need for any acknowledgement. Bit by bit we are all helping each other and increasing the knowledge and experience base. And that is a most wonderful altruistic thing.
Transformers are completely bi directional. Only the phase relationship between voltage and current changes when power flow reverses, so the transformer itself does not care either way.
The PWM switching part however, may or may not be bi directional, and it can be quite a complicated thing to analyse. It can sometimes work with mosfets, but not with most other types of semiconductor switching devices because mosfets can support current flow in either direction.
If it is demonstrated to work in this type of inverter, it obviously does work, and that is more by luck than anything else.
Most other types of PWM switching circuit topologies are not bi directional for power flow.
Cheers, Tony.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 02:08am 23 Sep 2017
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It's white mans magic, Oztules can't explain it either, but there is no doubt it is bi-directional.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
Posted: 04:01am 23 Sep 2017
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Using the formulae given in warpspeeds link above I got 1.3963 tesla for my dual aerosharp core toroid. It has a 74.2 cm sq core area. I used 100 turns for the secondary (230V) winding and there are 11 turns on the primary.
I'm curious why madness's tranny has a much lower Tesla figure?Klaus
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 08:39am 23 Sep 2017
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After a great deal of thought, what I think (?) may be happening is that current flows backwards through the inverse diodes in the four bridged mosfets.
If you replaced all four mosfets with diodes, then connected up 230v (from the grid) to the inverter output, then it just looks like a bridge rectifier that charges up the big electrolytic across the dc bus, and hence the battery.
This all happens at 50 Hz. The fact that one pair of mosfets is being furiously driven with PWM on the mosfet gates makes no difference. The reverse source drain diode just conduct leisurely at 50 Hz for each half mains cycle.
That all assumes that the PWM drive is in perfect synchronism with the reverse fed 50 Hz power, which it should be if the grid tie inverter providing the power is working properly. If the grid tie inverter does get out of synchronism *BANG*
But if a grid tie inverter gets out of synchronism when connected to the grid, that means *BANG* too.
So it works, but as is sometimes the case with some circuits, it can be operating in some completely unsuspected or unusual mode of operation. I could be very wrong about all of this, its just a theory.
But if its proven to actually work, then there is no denying that it does work. Trying to figure out how and why it works is a bit more of a puzzle. Cheers, Tony.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:18am 23 Sep 2017
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Normal practice would be to stack two cores and then wind it with half as many turns, but using much heavier wire, exactly as you yourself have done. That keeps the flux density about the same as original. Its the heavier wire that provides the power increase.
I was pretty surprised Mad's transformer too, but the low idling power some people are claiming for such monster transformers does suggest the flux density must be fairly low to achieve that.
Magnetising current is a very steeply rising curve with flux density. Once it saturates, the "curve" goes almost vertical towards infinite current limited only by the dc resistance of the primary. A small reduction in design flux density will give a dramatic reduction in magnetising current, and keeps you further away from the potential evils of mosfet destroying current surges during inverter start up.
Cheers, Tony.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 10:29am 23 Sep 2017
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Thanks for checking that Klaus, I went back and got the actual figures rather than working from memory. Correct result is 1.5103, CRAFT strikes again Edited by Madness 2017-09-24There are only 10 types of people in the world: those who understand binary, and those who don't.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 10:41am 23 Sep 2017
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Warp, not only is the current flowing back to the batteries it is doing it with regulation, AC voltages does not change significantly. As the available sunlight changes current flow changes with it, this also applies with the regulation of GTI we are doing also.
As I understand MOSFETs conduct bidirectionally so it seems the SPWM is able to regulate the voltage effectively. What is a mystery to me is the transformer primary is wound for 26V, well below the upper battery voltage of around 59V when charging.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: 12:01pm 23 Sep 2017
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Yes, mosfets conduct bi directionally when on, but when off there is still the source drain diode that can readily conduct, but obviously only in the reverse direction.
I was wondering about the voltage problem too. The primary turns needs to be sized so that the peak voltage is somewhat less than minimum end point battery voltage. Its rather a mystery how it can charge the battery unless the dc bus tries to go a lot higher than seems possible.
It "could" happen if the PWM switching causes some stored inductive energy somewhere to get pumped back into the dc bus as a higher voltage back emf.
Its somehow operating in some unexpected weird mode that is not immediately obvious. Cheers, Tony.
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 12:17pm 23 Sep 2017
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I believe the fets act as a synchronous rectifier, and with the windings, a boost converter.
Thats how it is able to push voltages of over 60v from a 28v winding with ease. There is no chance it is operating as a reverse transformer only.
Every instance of this topology will do the same thing as I understand it.
.........oztulesVillage idiot...or... just another hack out of his depth
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 12:30pm 23 Sep 2017
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That pretty well sums it up oZ. Although the exact mechanism is still a bit obscure.Cheers, Tony.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 07:55pm 23 Sep 2017
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Yes, more likely than the source/ drain diode theory. I doubt these diodes can handle much current. I did manage to blow one on a TO220 Mosfet when connecting drain/source legs backwards while passing 10A for ON resistance testing purposes.Klaus
Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429
Posted: 10:21pm 23 Sep 2017
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.
Edited by Clockmanfr 2017-09-26Everything 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
Posted: 07:54pm 27 Sep 2017
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Oztules, instead of 6v5 Zener diode for SCR can I use a 6v2 or 6v8 one? FR101 before LED: is there any special reason to be used there?Edited by brac321 2017-09-29OffGrid 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.
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 12:26am 28 Sep 2017
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yes 6v8 will work. It was just to get the voltage up for the shut down. The fast diode was....... I have thousands of them.
........oztulesVillage idiot...or... just another hack out of his depth
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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