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Forum Index : Electronics : Inverter building using Wiseguys Power board and the Nano drive board
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KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 11:42pm 15 Jul 2024
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wiseguy I understand exactly where you are coming from, this was not intended as a future wish list for a controller, just something some of us running two power boards could add ourselves if it was needed.
I'm simply exploring the chances of things to watch for when running with a second power board.
Agree with the Kilovac, only one needed, but in my case, it will only close if both cap banks are close to vbat.
You posted before about enabling the second power board drive if the power requirements needed it - that is simple to do and is a great idea, I think I would also have a manual override to engage 12kw mode if I was intending to start a very high induction Motor, again easy to do.
Cpos The idle power would be around single power board level when the SPWM drive is removed from the second Power stage, but I'm not sure if having the Toroids in parallel and one not running would cause an slight increase in current?
There would be no need for a soft start of the second power board if the inverter is running, in any case that is not possible if one power board is running, not without a full restart, and then both boards soft start as one, if both SPWM drives are enabled.
BTW: I expect wiseguy and poida to only solve firmware issues with the official firmware release, it would be totally unrealistic to expect anything else.
If anyone uses my modified code, I will be happy to sort any firmware issues out you may have.
Tribal Tronix The official code release and format is up to wiseguy and Poida, I'm sure they will advise you soon.
Back feed, again only something wiseguy can answer as I have never tried it or thought about, not something I have any need for. _ Edited 2024-07-16 09:46 by KeepISIt's all too hard. Mike.
Cpoc Regular Member Joined: 28/05/2024 Location: PortugalPosts: 78
Posted: 12:26am 16 Jul 2024
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Here is the EU if you want to back feed then AlL the equipment must be CE certified as for off grid that is not a requirement.
I will wait for wiseguy to give more clarity on the new pcb add on and its features however no need to rush this project. This project is getting to a point where you will have a very affordable and powerful yet feature rich and very reliable inverter solution. Best of all it can easily be swapped and even repaired for me that is the key feature. Also the ability to run up to 12KW is amazing for those power hungry motors or in my case MIG welder.
Cpoc Regular Member Joined: 28/05/2024 Location: PortugalPosts: 78
Posted: 12:27am 16 Jul 2024
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Here is the EU if you want to back feed then AlL the equipment must be CE certified as for off grid that is not a requirement.
I will wait for wiseguy to give more clarity on the new pcb add on and its features however no need to rush this project. This project is getting to a point where you will have a very affordable and powerful yet feature rich and very reliable inverter solution. Best of all it can easily be swapped and even repaired for me that is the key feature. Also the ability to run up to 12KW is amazing for those power hungry motors or in my case MIG welder.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 12:33am 16 Jul 2024
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I believe it's similar here, however most of the back feed discussed here is for off grid usage only.
My thoughts as well, I really looking forward to having that extra power capability without stressing the Inverter. Edited 2024-07-16 10:36 by KeepISIt's all too hard. Mike.
Cpoc Regular Member Joined: 28/05/2024 Location: PortugalPosts: 78
Posted: 01:20am 16 Jul 2024
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How would you back feed off grid. When I am thinking of back feeding energy aka selling back to the grid.Here in Portugal off grid just means that completely off grid with no utility power and battery backup. The utility is used only for charging your batteries or as a pass through but if used as a pass though them certified equipment is needed.
Back feeding means you don’t need batteries and you can sell the access solar back to the grid. Now it’s more like a scam and not worth it in my opinion
Off grid is a much better option as long as you have enough solar and batteries and no need for very expensive certified equipment.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 02:13am 16 Jul 2024
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First a quick discussion on Toroidals and parallel connection. If a toroidal is being energised with AC at near its intended voltage then it is dissipating the magnetising current. The only way to reduce idling current to the secondary stage is to isolate the primary and secondary from the AC.
The primary is easy we turn off the opto drives and the FETs can be powered up joined to the primary but with no opto drives there is no primary excitation. So that leaves the secondary lower currents but higher voltage but it needs to be isolated from the first stage mains output to kill its idling magnetising dissipation. Ok we put a relay between the two secondaries but who wants to be in close proximity to that relay when the second transformer is connected to No 1 stage when it was already left fluxed up in the same direction we are about to re flux it in?
Now then, how do we connect the secondaries in parallel, please bear with me here, so we get a light 50W - 250W and with a secondary relay circuit we connect the lamp or resistor or chopper PWM what ever starts with a controlled low current and as the transformer fluxes up the lamp dims etc as less current is drawn until there is only idling current flowing, now we close the full high current connection for true parallel and then enable the FET drive optos. I see this as a process that could be done within a second or two.
KeepIS has been looking over my shoulder I reckon because that was my thinking, if you know you need power flick a manual switch to bring in the secondary (still using the gentle start mechanism) at your call and then flick it back to auto when finished. If left in Auto and more than 5 or 6 KW is being asked for then a slow start is fine for the second stage to come in and share the load.
For large momentary loads the single stage is fine for a few seconds at two or three times its rating and if the load is still there the second stage is already helping. That is essentially how I would have the 2 stage inverter operating. Edited 2024-07-16 12:15 by wiseguyIf at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135
Posted: 02:19am 16 Jul 2024
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That wasn't the question.
He wants to use it as a charger from the grid.
However the fact that it is capable of sending power back to the grid would require it to have certification, unless he means an isolated micro grid.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 02:38am 16 Jul 2024
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Tribal Tronix sounds like he wants to run a mini (micro?) grid that is not connected to a utility power source. I will have to leave it to Murphy or possibly Poida or Madness to answer that as I have not tried to do it. Last I heard of someone doing this and having issues was Madness with a Nano inverter and it not back charging the batteries nicely. Whether that was due to his specific implementation of the Nano circuit I can't comment on. In theory it should work but as I said I have not tried it yet.
Even if it is determined that it works, I believe the scheme needs to be monitored externally to stop any over charging of the batteries, as with a GTI operating from the solar the back feeding is a by product, if you have more solar than any connected loads are using the rest just tries to back feed through the inverter.
With regard to the software, that belongs to Poida, he has spent a considerable amount of effort and time to create it. I suspect it will be available in due course to download and use (or modify) at your own risk, I would also guess that this is maybe a week or two away but Poida may have more to say on this.If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
Cpoc Regular Member Joined: 28/05/2024 Location: PortugalPosts: 78
Posted: 02:59am 16 Jul 2024
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Wiseguy thank for the explanation. I like the feature of the manual and auto setting switch.
Cpoc Regular Member Joined: 28/05/2024 Location: PortugalPosts: 78
Posted: 03:01am 16 Jul 2024
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Double post again. Spotty internet wifi connection. Edited 2024-07-16 13:09 by Cpoc
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 04:16am 16 Jul 2024
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Just finished removing an old and installing a new washing machine
Wiseguy, do you have any "rough" idea of the % of magnetizing current involved with paralleled Toroid secondaries with one not driven? Or is more like test it and see.It's all too hard. Mike.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 05:13am 16 Jul 2024
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Not sure of what you are driving at. I prefer to relate the discussion back to the DC battery input.
If I have one transformer idling at my chosen mains voltage I am using E energy from the battery source. If I have 2 transformers at my chosen mains voltage input energy is 2E.
If I am driving the primary or secondary the magnetising energy should be essentially the same. What we need to be careful of is the peak inrush energy depending on the state of the second Toroid when we removed the drive compared to when we reconnect it.
I have been investigating inrush current limiters such as SL32 10015-B (Digikey) ~ $2.06 USD ea rated for 10R and 15A continuous and 150Joules. 2 or 3 in series is 20R or 30R total and they would have a combined 300 or 450 Joule rating, and for 3 units a max peak current of ~ 11.5A worst case for 1 cycle reducing after that for each cycle.
So 2 relays are needed, a 16A one for inserting the NTC inrush limiters and another 30A one to short the two secondaries as one. A bit of current sensing and some timing circuitry and voila job done? Edited 2024-07-16 15:15 by wiseguyIf at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135
Posted: 05:22am 16 Jul 2024
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The core doesn't care which winding is energising it (it's not connected to either). As the voltages on the windings will be the same the power loss will be the same, so total core losses are double. The magnetizing current drawn from the battery will be double. It is just that it is getting to the second transformer via the first instead of directly from the FETs.
Edit. Given that KeepIS's inverter can handle large induction motors stopping and starting at random points in the cycle, the stators of which can also hold remanent flux, will it be any worse? Edited 2024-07-16 15:33 by phil99
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 05:43am 16 Jul 2024
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Thanks, that all makes sense now. I now have a few options to think about.
This last piece of information allows me to correctly size and build the twin Toroid dual choke housings.
I will have a separate single housing for the both Toroids AC metering and secondary AC soft start control for the second Power board, should the inverter be in half power mode.
I have a feeling that this inverter will be idling in Full power mode most of the time, if idling current is twice the single toroid magnetizing current, that would add another 17w to 19 watts, it would be meaningless with the size of the battery bank and solar that we have, and considering our 300w to 800w night time loads.
But just in case - I'll have the option.
EDIT Hi Phil, thanks for that input, they are good points, but I think I'll err on the side of keeping those currents to a minimum if I can, should I decide to run in low power mode. _ Edited 2024-07-16 15:48 by KeepISIt's all too hard. Mike.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 06:28am 16 Jul 2024
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Phil, I feel like you are correcting something I wrote, but when I compare the two posts to me they are saying exactly the same thing ? If you consider something I wrote was incorrect what was it?? I referred to the supply energy being double for 2 cores and not which winding caused it.If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135
Posted: 06:35am 16 Jul 2024
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Sorry, not intentional. Your post wasn't there when I started writing the first part mine so I thought I was replying directly to KeepIS.
The Edit was after I saw your post.
nickskethisniks Guru Joined: 17/10/2017 Location: BelgiumPosts: 458
Posted: 08:37pm 16 Jul 2024
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Nice where this is going, do we stay here or do we open another thread for discussing a double powerboard inverter?
My plan was to build a normal inverter because I want to switch to one that can be started by anyone. Then I wanted to build up a second one with 2 powerboards and transformers, because too much is electrified and I would like the idea to switch off a powerstage to safe energy, for me this is important in the winter. Lately I was thinkering to build a hf powerstage to support the main inverter, but now I see there is interest in a silly high LF inverter I want to help and contribute.
I follow Mike when he's says this is it, building a double powerboard with this controllerboard must be seen as 1 inverter. If you want all functions a double powerboard/transformer can provide I personally think the nano has reached it limits, I would want more IO's on the controllerboard, like extra temperature sensors for example. For sure the IO's of a nano can be expanded but might cost more or would increase programming complexity then a bigger mcu.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 10:29pm 16 Jul 2024
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I don't think we need to go that far. I've had time to think about this a bit more, and I'm very familiar with this power stage and Nano controller now. The two extra things that I want to monitor with the second power stage and toroid can be easily accomplished on the Nano.
Not only that, but if someone really wanted to have extra IO control for any reason, that could be made simple without the need to change the current controller.
I'm on my way out for a brisk 10km walk, so I'll expand on that later today. just short on time at the moment.
Great to see others interested in Wiseguys dual power stage and the possible benefits. It's all too hard. Mike.
Cpoc Regular Member Joined: 28/05/2024 Location: PortugalPosts: 78
Posted: 10:47pm 16 Jul 2024
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Can you upgrade from 2 temperature sensors to 4 temperature sensors. 2 for transformers and 2 for the mainboards ? Are they enough pins available ?
mab1 Senior Member Joined: 10/02/2015 Location: United KingdomPosts: 209
Posted: 12:18am 17 Jul 2024
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As a thought experiment i considered this concept of having a dual transformer powerboard setup, but with dissimilar transformers:- i.e. a small one (say, 1 to 3 kva) with a low volts/turn and low core loss for light/overnight loads, and a big one (say 6kva) with a high volts/turn and higher loss to do the heavy lifting during the day. The obvious question is how will they share the load when both are on? But i think the big transformers lower d.c. resistance should take care of that, particularly as the higher volts/turn corresponds to less copper resistance. Also it wouldn't really matter if the big transformer took more than its 'fair share' as long as it was big enough to take the load.
For myself i can live with the losses of a 6kva anyway so I'm not trying to get you geniuses to make this work for me , but if you are going to the effort to make this dual system work, it might give more benefit with dissimilar transformers.
On a different subject:- i do intend to use grid tie inverters to backfeed if possible, so i would be very interested if someone tries it (otherwise i might be the first - but not for a while yet ).
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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, but if you are going to the effort to make this dual system work, it might give more benefit with dissimilar transformers. 
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