Warpverter: How would I build a second one?

[Warpspeed]

This might be a lazy question that I could just read snd learn for myself, but if the warpverter community would throw me a bone with a free preview: Does the DIY transformer winding aspect arise out of necessity for a lack of commercially available solutions or is it just driven by the natural extension of the DIY mentality?

Or to put it more plainly, if I get into a warpverter project one day in the 6-10kW range and maybe 48-96v range on the DC side, will I have the option to just pay a premium to buy high quality prewound toroidal transformers from a reputable USA distributor? Or will I likely find that the exact winding count I'm looking for is not commercially available?

Oh and also does a split phase 120/240 warpverter design with a center tapped neutral exist already or would I need to feed the whole thing through another transformer for that?

Edit: Oh I should at least read the very thread I'm in before asking questions. Thanks guys.

The DIY winding exercise is mainly about massively reducing cost, and to build a much more electrically efficient transformer to your own exact requirements.

So far all of the Warpverters built have been outside the USA, and do not require the 110/220v split phase system that America uses.
Its no more difficult to wind four suitable transformers for split phase operation than for single phase operation.
You still only need to have four transformers to generate split phase directly.

 

[Pecks7608]

Keep an eye out for a largish heatsink

Keep an eye out for a largish heatsink

Large, large ish and OMG I have in abundance. Everything from inverter size to 1m long. It's all the little fet sized ones I struggle to find.
It's starting to get dark so I tunneled through my shed for those IGBTS. Here's a couple pics. I threw in a pic of the monstrous heat sink on the back of these things. There's what I think is an emi filter as well.
I'll post again after I get cleaned up.

 

[doing it different]

The DIY winding exercise is mainly about massively reducing cost, and to build a much more electrically efficient transformer to your own exact requirements.

So far all of the Warpverters built have been outside the USA, and do not require the 110/220v split phase system that America uses.
Its no more difficult to wind four suitable transformers for split phase operation than for single phase operation.
You still only need to have four transformers to generate split phase directly.

And if I understand correctly all 4 transformers need to be wound in a split phase?

I find this warpverter stuff super interesting....
its abit above my understanding, especially the IGBTS and controls...

I have always thought there needs to be a simpler way to make an inverter, that's tough and easy to fix.
if I get some of my many other projects done. This is something I would love to tackle...

 

[Warpspeed]

And if I understand correctly all 4 transformers need to be wound in a split phase?have always thought there needs to be a simpler way to make an inverter, that's tough and easy to fix.
if I get some of my many other projects done. This is something I would love to tackle...its abit above my understanding, especially the IGBTS and

The primaries are going to all be exactly the same, split phase or single phase.
Each secondary will be split into two separate windings, each having half the original single phase design voltages.

A single phase Warpverter has four transformers with secondary design voltages of 225v, 75v, 25v, and 8.33v.
When all of these are connected in series, the combined output will be a 236v RMS single phase sine wave.

A split phase Warpverter also has four transformers, but the largest transformer instead of having a single 225v secondary winding will have two separate 112.5v windings. Transformer two has two 37.5v windings instead of a single 75v winding. And so on.

If you connect one set of these four windings in series you get 112.5v, 37.5v, 12.5v, and 4.165v. When all connected in series that will create a 118v sine wave.

Then you connect up the second set of four windings in series, and that will also generate an identical 118v sine wave which is separate and isolated from the other 118v sine wave output.

The two isolated 118v sine wave outputs can then be connected in series to generate the required 118/236v split phase output.

These voltages are all nominal design figures, the actual final voltages can be adjusted up and down in a working inverter with a potentiometer to 110/220v or 120/240v or whatever you decide.

 

[rogerdw]

I have always thought there needs to be a simpler way to make an inverter

Haha ... well here's one.

 

[hwy17]

@rogerdw Tell me if you don't want general beginners Q&A clogging up your thread. But otherwise I'll just assume this is where the party's at.

The warpverter has taken up residency in my mind lately as we face the reality that the Xantrex XW series may not be around forever. I had a bit more of a look today and here's what I'm stuck on.

1. Is everybody DIY designing their own control boards or is there prior work we can copy? The transformers I understand the basic concepts now, the power switching electronics I can begin to imagine. PCB's are out of my current knowledge. I see there is a github with a "stepinverter" design documented. Is this applicable, acceptable, and up to date for a current maybe 6kW warpverter? Are there any other precisely documented designs? Do warpverter builders order these control boards custom manufactured or are you doing your own PCB work?

2. How many VA should the largest transformer core be able to handle to make a 6kW or 10kW warpverter? I looked at a custom transformer manufacturer in California and the largest toroidal in their catalog is 10kVA. I understand toroidal is a possible preference but may or may not be a requirement. I imagine I would also probably prefer to use toroidals unless I found it too difficult to aquire them.

3. In a description I saw elsewhere there was something about the warpverter design modulating itself somewhere other than most other inverters. The part about varying load levels slightly varying output voltage due to transforming characteristics I understand. But what's the difference referenced there, where do most other inverters sense the load and where does the warpverter do it? I have a particular bug bear in my imagination about control logics getting into sustained overcorrection cycles and I am particularly interested in the idea that warpverter might be able to fundamentally circumvent this problem.

 

[rogerdw]

Large, large ish and OMG I have in abundance. Everything from inverter size to 1m long.

That's excellent. Imagine having to pay full retail for any of them ... almost enough to put you off starting.

FS50R12KT4P_B11 ... 1200 V, 50 A sixpack IGBT module ... datasheet

That's 50A continuous ... but 100A repetitive.

I suppose we could use just four of the igbts in each package. Dunno, that's not my area of expertise.

AUD $269 +126 freight from US to Aus each! $200-225 each from China on ebay..

If they could be used, there's an immediate $1,000 saving in your build.

 

[rogerdw]

@rogerdw Tell me if you don't want general beginners Q&A clogging up your thread. But otherwise I'll just assume this is where the party's at.

You're perfectly welcome to join in and ask what you need ... and all good questions.

1. Is everybody DIY designing their own control boards or is there prior work we can copy? The transformers I understand the basic concepts now, the power switching electronics I can begin to imagine. PCB's are out of my current knowledge. I see there is a github with a "stepinverter" design documented. Is this applicable, acceptable, and up to date for a current maybe 6kW warpverter? Are there any other precisely documented designs? Do warpverter builders order these control boards custom manufactured or are you doing your own PCB work?

Warpspeed (Tony) designed the Warpverter and supplied a blank control board plus the ROM with lookup tables used for control.

The github "stepinverter" plans I have seen were from an early 24v version by one of the guys on thebackshed forum. I would definitely stick to Tony's circuit which he shows here.
Tony's Warpverter is I believe a 5kW and mine is a 15kW ... using effectively the same circuit ... just bigger transformers . Though I used mosfets (cheaping out) while Tony used IGBTs for the larger two and mosfets for the smaller two inverters.

Some of the other builders built their own control boards using Arduino Nano modules ... but I didn't want to take any chances, so stuck with the original control board which is still working perfectly well 8,000kWh later. Plenty of time to reinvent the wheel later, though I have no plans to risk it. Man's gotta know his limitations.

2. How many VA should the largest transformer core be able to handle to make a 6kW or 10kW warpverter? I looked at a custom transformer manufacturer in California and the largest toroidal in their catalog is 10kVA. I understand toroidal is a possible preference but may or may not be a requirement. I imagine I would also probably prefer to use toroidals unless I found it too difficult to aquire them.

Tony's the man to give exact details but the largest inverter and toroid do the bulk of the work and the others are progressively about one third smaller in capacity. If you used a 10kVa toroid for the largest ... that would be a great start for a 13 or 14kVa inverter I would suspect.

I used toroids for mine and Tony used EI types for his. Obviously both can work ... depends on being able to source or build them.

Again, Tony can give precise details for winding etc ... so it's not that far fetched to maybe wind your own. I'd never wound a toroidal transformer before I did these and I found it relatively easy. Took a while, but I'd have no fear in doing it again.

3. In a description I saw elsewhere there was something about the warpverter design modulating itself somewhere other than most other inverters. The part about varying load levels slightly varying output voltage due to transforming characteristics I understand. But what's the difference referenced there, where do most other inverters sense the load and where does the warpverter do it? I have a particular bug bear in my imagination about control logics getting into sustained overcorrection cycles and I am particularly interested in the idea that warpverter might be able to fundamentally circumvent this problem.

It doesn't have a voltage feedback system at all ... it uses a feed forward design. It is described in the other thread I linked to with the circuit above.

In my unit I was supposed to be able to run it from a low of 44v up to 88v ... but I find if the voltage gets below 46v ... it does hunt a bit. I must have pulled a clanger in my calculations somewhere. Maybe 40-80v would have been a better choice.

I have been going to fit a modification to attempt to address that, but haven't got around to it yet ... too slack ... plus I simply don't let the battery to get below 46v. Easy!

With summer starting here I want to fit the mod so I can run our huge aircon system. It's about 140 (wiring) metres from the inverter ... and draws 100a at startup ... and drops the voltage to ~215v instead of 240 ... so to have some compensation for that will be good.

Plus I plan on fitting a soft start unit to the aircon to reduce the startup current. The Warpverter can certainly supply the 6kW of power the aircon needs ... it's the startup that's the issue.

 

[Warpspeed]

Ah Roger, you beat me to the draw

1. Is everybody DIY designing their own control boards or is there prior work we can copy? The transformers I understand the basic concepts now, the power switching electronics I can begin to imagine. PCB's are out of my current knowledge. I see there is a github with a "stepinverter" design documented. Is this applicable, acceptable, and up to date for a current maybe 6kW warpverter? Are there any other precisely documented designs? Do warpverter builders order these control boards custom manufactured or are you doing your own PCB work?

Quite a few ways to go about it, but the easiest for me would be if you can PM me and we can get in touch by e-mail.
I can then e-mail you the necessary Gerber files that you can use to order your own bare circuit boards direct from China.
The only other thing you really need from me will be the pre programmed EEPROM chip that contains the 256 different lookup tables.
Everything else (apart from the transformers) are all basic commonly available components.

2. How many VA should the largest transformer core be able to handle to make a 6kW or 10kW warpverter? I looked at a custom transformer manufacturer in California and the largest toroidal in their catalog is 10kVA. I understand toroidal is a possible preference but may or may not be a requirement. I imagine I would also probably prefer to use toroidals unless I found it too difficult to aquire them.

That is a very good question !
First thing is to establish a desired final output power goal.
Let's assume 220v 8Kva, first convert that into required output current. 8K/220 = 36 amps rms in all of the series secondary windings.
Largest inverter 225v 36amp secondary = 8.1Kva if its for split phase, two 112.5v 36 amp secondaries, still 8.1Kva.
Second inverter 75v 36 amp secondary = 2.7 Kva
Third inverter 25v 36 amp secondary = 900 va
Fourth inverter 8.33v 36 amps 300 va

That is a hell of a lot of Va's, far more than the projected 8Kva combined power output.
The reason for that is that some of the inverters are working in direct opposition to other inverters to generate the stepped output waveform.
There is a LOT of circulating power within the inverter. The actual total combined losses are surprisingly low, the overall power efficiency input to output is quite comparable to a PWM transformer inverter, but the transformers still have to carry all this extra circulating power and must be sized appropriately.

Toriods can be stacked without any real limit if hand winding.
The commercial toroids are all machine wound, and stacking is usually not possible because the winding machine will simply not fit through what becomes a deep tunnel instead of a shallow hole, if you know what I mean.
It may be cheaper (?) to use grain oriented silicon steel E and I stamped laminations.
But you will need to get some quotes either way. Or you can mix transformer types if that is more convenient.

I must confess I used the Silicon Iron laminations in my own Warpverter, and a dear friend of many years that owns a transformer business did it all for me to my design, for just the cost of the materials. I am now well into my seventies and am no longer the man I once was, and so I wimped out. Anyhow, I did not have any suitable toroids at the time here anyway, and that is my excuse and I am sticking to it

3. In a description I saw elsewhere there was something about the warpverter design modulating itself somewhere other than most other inverters. The part about varying load levels slightly varying output voltage due to transforming characteristics I understand. But what's the difference referenced there, where do most other inverters sense the load and where does the warpverter do it? I have a particular bug bear in my imagination about control logics getting into sustained overcorrection cycles and I am particularly interested in the idea that warpverter might be able to fundamentally circumvent this problem.

All other inverters that I am aware of use some kind of voltage feedback to maintain a fairly constant output voltage, regardless of changes in incoming dc voltage and load current. That is fraught with problems, even measuring an ac voltage is not that simple, it involves some kind of averaging. And then designing a feedback loop that is both reasonably fast responding and stable not that easy either.
Its not a simple thing, and the result is usually light flicker when the refrigerator starts up.

I thought about all this for a very long time and have come up with an entirely different approach to the whole problem.
It will be appreciated that as the transformer ratios are fixed, switching all the inverters on and off at appropriate times will generate a low distortion sine wave output that is directly proportional to the dc input voltage.
We can change that dc input/ac output voltage relationship by jumping between different lookup tables in a ROM.

It then becomes possible to measure the incoming dc input voltage, and then jump to the exact lookup table required to generate the required ac output voltage. That can all be done very quickly without complication. Its called feed forward correction, it has a similar effect as feedback and corrects perfectly for changes in dc input voltage, fast or slow. It will drive all the transformer primaries to generate a constant amplitude sine wave output from the inverter without needing to actually measure the inverter output voltage.

The big advantage is very rapid speed of response and total stability.
The disadvantage is that there is going to be some voltage sag with increasing load due to the non perfect voltage regulation through the transformers. All transformers do it, and its not terrible.
The grid goes up and down anyway all the time and everything works fine.
What is really objectionable are massive rapid voltage sags and surges often the result of crappy and slow voltage feedback.

So the Warpverter can correct for sudden step load changes very quickly indeed, but the voltage will definitely drop by a few volts with increasing inverter load. Even that can be fixed fairly easily by adding feed forward current correction. That requires a Hall current sensor in the incoming dc a couple of resistors and a potentiometer. That adds extra feed forward current (load) correction over and above the voltage feed forward correction.

I have not bothered to fit that to my own Warpverter. The improvement is there, but my Warpverter has now not missed a beat in almost seven years of continuous operation, and I cannot be bothered making a new control board for it. I did mock up the circuit and it worked very well, but there are other more interesting projects to explore.

 

[tinyt]

.... snip ....
2. How many VA should the largest transformer core be able to handle to make a 6kW or 10kW warpverter? I looked at a custom transformer manufacturer in California and the largest toroidal in their catalog is 10kVA. I understand toroidal is a possible preference but may or may not be a requirement. I imagine I would also probably prefer to use toroidals unless I found it too difficult to aquire them.

....snip....

If you are going to have transformers made, don't forget about idle power draw. Just my two cents.

 

[Warpspeed]

Good point Tim.

To get transformers wound, you can always do the design and tell them exactly what you want done.

If they design it for you, just INSIST on it having a one Tesla maximum design flux density.
They will bitch and moan and say that is stupid, but dig your heels in and demand one Tesla flux density.

That will guarantee a low idling power.
How low, depends on the quality of the core material, and there is a bit of luck involved there.
But idling power WILL end up being acceptably low.

 

[hwy17]

@rogerdw @Warpspeed

This is fantastic you guys. This unlocks the parts of the process of that I was stuck on. So we do have a golden board design, the power bus and switching bones we get to exercise our creativity on, and the core tech is available on a chip if we're ready for it.

I try to be careful about how many things I consider doing in life because there's not time for all of them, but I might get hooked on this one now that I'm running out of things to do with the DIY batteries other than just buying more of them.

We'll see if that happens though. I'll continue reading into the switching hardware to see what I can imagine and PM you Warp if I get anywhere close to the idea that I can actually make a go of this.

Now one question I have is getting a ready baked chip from you sounds great and the best option for me, but in case you retire to a beach without internet one day, is your code available to us? I don't have an automatic expectation that it should be available with free and unlimited license, just curious how confident we can be that we'll be able to get replacements in the future.

 

[hwy17]

Does idle power in this context apply only at idle or does the idle draw indicate an ever present loss at all load levels? By all means I would try to design to best practices I'm just curious how it applies because my inverter doesn't idle, I would build something in the 5-10kW range and my load never falls below 500 watts.

 

[Warpspeed]

Now one question I have is getting a ready baked chip from you sounds great and the best option for me, but in case you retire to a beach without internet one day, is your code available to us? I don't have an automatic expectation that it should be available with free and unlimited license, just curious how confident we can be that we'll be able to get replacements in the future.

The chip itself is only worth like a couple of dollars, but its a 256 x 8 (2meg) prom. Easiest to just drop one into the mail to you.
If someone can figure out a way to make a 2 meg file dump available on the internet, that would be great.
That is beyond my own ability. I hope that will happen one day.

Quite a few people now have these proms running in their Warpverters, so if something ever happens to me, there are enough people out there and a slowly building interest, that all of the knowledge on various Forums, it has now become pretty much free open source public domain, and self sustaining without my input.

That is also why I am more than happy to provide Gerber files for the PCBs free.
These can also be passed around freely without any restrictions.
I really do not want to sell circuit boards !!!
What I wish to see is the whole thing to take on a life of its own, and become a popular way to build a really solid reliable repairable high power inverter without containing any secret mysterious software.

Over the years I have tried to help people to do things they otherwise may not have been able achieve without some help.
Money means nothing to me. None of this has ever been for personal profit.

Three different things have brought to me a very great deal of personal satisfaction and a very modest amount of fame over the years.

First was twincharging, using both a supercharger and a turbocharger together for truly remarkable performance.
Google "warpspeed twincharging" if you are a petrol head, I have been a bit of a pioneer in that field.

Second is the PTS flow bench Forum.
That has become the number one go to Forum for anyone wishing to build an air flow bench for developing performance cylinder heads. I post over there as "Tony" with Warpspeed in my signature. Literally many hundreds of successful professional quality home built airflow benches are now in operation around the world, and have been built by hobbyists, racers, and engineers, hot rodders, and even some high dollar professional race teams in many diverse forms of motorsport.
I designed all the flow bench electronics that everyone now uses, its all been a fantastic success and has made a lot of people extremely happy including me.

Third is the slow long term development and introduction of the Warpverter.
Its been rather slow to take off, but I think long term it might have quite a future as more people learn about it and more are successfully built. Time will tell.............

 

[Warpspeed]

Does idle power in this context apply only at idle or does the idle draw indicate an ever present loss at all load levels? By all means I would try to design to best practices I'm just curious how it applies because my inverter doesn't idle, I would build something in the 5-10kW range and my load never falls below 500 watts.

Idle power is an ever present loss that never goes away.
Conduction and switching losses both increase with power level.

 

[hwy17]

The chip itself is only worth like a couple of dollars, but its a 256 x 8 (2meg) prom. Easiest to just drop one into the mail to you.
If someone can figure out a way to make a 2 meg file dump available on the internet, that would be great.
That is beyond my own ability. I hope that will happen one day.

Quite a few people now have these proms running in their Warpverters, so if something ever happens to me, there are enough people out there and a slowly building interest, that all of the knowledge on various Forums, it has now become pretty much free open source public domain, and self sustaining without my input.

That is also why I am more than happy to provide Gerber files for the PCBs free.
These can also be passed around freely without any restrictions.
I really do not want to sell circuit boards !!!
What I wish to see is the whole thing to take on a life of its own, and become a popular way to build a really solid reliable repairable high power inverter without containing any secret mysterious software.

Over the years I have tried to help people to do things they otherwise may not have been able achieve without some help.
Money means nothing to me. None of this has ever been for personal profit.

Three different things have brought to me a very great deal of personal satisfaction and a very modest amount of fame over the years.

First was twincharging, using both a supercharger and a turbocharger together for truly remarkable performance.
Google "warpspeed twincharging" if you are a petrol head, I have been a bit of a pioneer in that field.

Second is the PTS flow bench Forum.
That has become the number one go to Forum for anyone wishing to build an air flow bench for developing performance cylinder heads. I post over there as "Tony" with Warpspeed in my signature. Literally many hundreds of successful professional quality home built airflow benches are now in operation around the world, and have been built by hobbyists, racers, and engineers, hot rodders, and even some high dollar professional race teams in many diverse forms of motorsport.
I designed all the flow bench electronics that everyone now uses, its all been a fantastic success and has made a lot of people extremely happy including me.

Third is the slow long term development and introduction of the Warpverter.
It's been rather slow to take off, but I think long term it might have quite a future as more people learn about it and more are successfully built. Time will tell.............

I fancied myself as a petrolhead, but I never quite had the wherewithal to get on top of a car and actual performance mod it. Always just played catchup with maintaining them. Still had fun though and daily drove some fun cars - 1st gen MR2, E30, NA Miata, and now a Chevy SS (Commodore). All manual transmission.

Nowadays I've rediscovered the yz125 I abandoned as a teenager and I find it more rewarding to work on that where I can do everything with my hands compared to difficult and heavy cars. Maybe I'll get to the point where I can flow chamber that one day.

I do think the warpverter has the potential to create a self sustaining community and that's why I was particularly wondering if you're ever releasing your code or ROM or whatever it is so we can also flash it ourselves in the future, but maybe when I learn more I'll see that itself is not a secret key that the community is dependent on either.

 

[Warpspeed]

I do think the warpverter has the potential to create a self sustaining community and that's why I was particularly wondering if you're ever releasing your code or ROM or whatever it is so we can also flash it ourselves in the future, but maybe when I learn more I'll see that itself is not a secret key that the community is dependent on either.

I would like to release it, but don't really know how to do that
Nothing secret about it. In fact at least two different people have both developed their own Nano boards to do in software exactly what my hardware board does. These are both 100% plug compatible and functionally identical to my own board. Its plug and play quite literally.
I have those boards here and cannot tell which is actually running my Warpverter without actually looking.
First picture is the Nano board, the pink and brown wires are the twisted pair opto coupler drive to the bridges.
Second picture is my (software free) ROM driven hardware logic control board.

Its built a lot larger than it really needs to be, into a modified two drawer filing cabinet. It opens up and everything is exposed, clearly visible, and very easy to work on. Never actually had a fault yet to fix !
I think its one of Murphy's laws that anything that is easily accessible and readily replaceable, and you have a spare, never fails.
The legendary Murphy was a very wise fellow.

If someone that has a website wishes to post my Gerbers and a hex dump of the EEPROM that would be wonderful.
The wider the exposure this all gets the better.

If anyone wishes to re-post any of my Warpverter pictures somewhere else on another Forum, go for it !

 

[hwy17]

The wider the exposure this all gets the better.

If that's the intention I love it. Just didn't want to make assumptions. I'll PM you.

 

[Pecks7608]

That's excellent. Imagine having to pay full retail for any of them ... almost enough to put you off starting.

FS50R12KT4P_B11 ... 1200 V, 50 A sixpack IGBT module ... datasheet

That's 50A continuous ... but 100A repetitive.

I suppose we could use just four of the igbts in each package. Dunno, that's not my area of expertise.

AUD $269 +126 freight from US to Aus each! $200-225 each from China on ebay..

If they could be used, there's an immediate $1,000 saving in your build.

This thread has me all over the place in my head space. I'm just now figuring out I can respond to individual questions or comments as I read. So bear with me.
If I'm understanding the mppt then the UGBTs I have might be better utilized there. I've drug this feed all over the place though so I'll try to stay on topic.

And if I understand correctly all 4 transformers need to be wound in a split phase

My 2 cents onsplit phase: Unless you intend on run one or the other it's not worth worrying about. That is unless of course the warpverter does something different I'm misunderstanding. Our stoopid split phase is hard on transformers. In the 120/120 configuration you start having issues when the loads are unbalanced by more than 20%. Which is easy to do. Even if you build a 20k transformer that's 2,000 watts on a leg.

If they design it for you, just INSIST on it having a one Tesla maximum design flux density.
They will bitch and moan and say that is stupid, but dig your heels in and demand one Tesla flux density.

I can confirm this. 1 Tesla is the way to go. My first attempt at a transformer using old PJ cores wound to 1 testla has a 26 watt idle.

 

[hwy17]

Our stoopid split phase is hard on transformers. In the 120/120 configuration you start having issues when the loads are unbalanced by more than 20%. Which is easy to do. Even if you build a 20k transformer that's 2,000 watts on a leg.

Would that be true for a split phase toroidal warpverter? My 6.8kW Schneider XW uses a single toroidal transformer and it's rated for 4.8kW on one leg with no load on the other.

Is the winding scheme on the XW different than what's proposed for a split phase warpverter or is the XW's core just oversized to accommodate that?

 

[hwy17]

If one was ordering custom manufactured toroidal transformers for a warpverter, with a design DC operating range of 35-70V and 120/240V output, what would be the specified primary voltage and is it identical for all four transformers?

 

[Warpspeed]

If one was ordering custom manufactured toroidal transformers for a warpverter, with a design DC operating range of 35-70V and 120/240V output, what would be the specified primary voltage and is it identical for all four transformers?

For 35v dc minimum all the primaries would be designed for 35v rms 50/60Hz with your on line transformer design software.
Largest transformer, primary 35v rms, secondary 225v rms (or two 112.5v secondaries for split phase).
Turns ratio would be 225/35 and it needs to be as exact as you can make it.

Juggle the turns up and down a bit on both primary and secondary to get the turns ratio as exact as you can make it.
The waveform steps will be 8.3v per step, so try and keep all of the secondary voltages to be within about one volt which should not be difficult.

Only other thing you need to do is to set the voltage operating range of the control board.
Select the appropriate resistors and potentiometer which set the range of the analog to digital voltmeter.
With the potentiometer set mid scale, input to the A/D converter chip should be 2v to 4v with 35v to 70v dc input.

I see no reason why a Warpverter set up for split phase should have any limitations on loading per leg.
It would also be possible to parallel both 120v outputs and get full rated power at 120v if you wished to do that.
For Americans, split phase would definitely be the way to go even if you don't really need it. Later you might regret not doing it.

I will start putting together an e-mail for you after breakfast

 

[tinyt]

If one was ordering custom manufactured toroidal transformers for a warpverter, with a design DC operating range of 35-70V and 120/240V output, what would be the specified primary voltage and is it identical for all four transformers?

Also tell them that the waveform is square wave not sine wave. The formula is slightly different I think.

 

[hwy17]

For 35v dc minimum all the primaries would be designed for 35v rms 50/60Hz with your on line transformer design software.
Largest transformer, primary 35v rms, secondary 225v rms (or two 112.5v secondaries for split phase).

Thank you. So spec the transformers for the minimum expected input voltage?

Say you were dealing with a 16S Lifepo4 and in my mind for the batteries the voltage range is 44-55v. What spec would you be inclined to design the warpverter for, like lean up towards 40-80v or down towards 35/70v? I believe I'm receiving @rogerdw 's warning correctly not to cut it so close as to set it right at 44.

 

[hwy17]

Also tell them that the waveform is square wave not sine wave. The formula is slightly different I think.

Yeah I'm still ingesting the concept of transforming square wave AC at all. I'd always imagined the transformer magic relied on at least some kind of coherent wave to generate the mysterious spinning electric fields.

Which is just to say thanks and my gut is not surprised if the answer is they both work but they're different. This further contributes to my feeling that I'm just not gonna even dip my toes into trying to design or wind my own.