OzInverter Build

Topics concerning inverters for on or off grid use. DIY and OEM.
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Jack Bauer
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OzInverter Build

Post by Jack Bauer »

As some of you may know I hate re inventing the wheel so went about a search to find a high power dc to ac inverter that could be built, upgraded and maintained at home. Perhaps knowing its usefullness was at an end my pos Victron 3kw decided to pop a row of mosfets over the weekend. Surprise surprise. Anyway, my search has led me to the Ozinverter detailed here :

Purchased the book and a few days later the boards which have arrived today. Naturally I'll be doing things a little bit differently but will document the build and process here and of course with uber boring videos.
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Re: OzInverter Build

Post by Pete9008 »

Watching with great interest. Had been wondering whether it would be possible to repurpose a Prius inverter to do something similar but this looks like a much better solution.
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Re: OzInverter Build

Post by lompilomp »

Haha I figured you were looking into home power AC inverters, saw one of those chinese diy ones on your bench on the GS300h video you made a couple days ago.

I've always been fascinated with the idea of going fully off grid but as always I kind of take it a little too far, and end up biting SLIGHTLY more than I can chew... Like I ended up trying to use 1000A 1700V IGBT bricks to make a 220v inverter... The same IGBT's that are used in multi MW wind turbines to run an inverter that would probably never see more than 20kw in its life.

Honestly almost did it too, but the switching frequency of the EG8010 is 23Khz, and the gate driving is what killed me. These bricks have way too much gate charge. I even have all the stuff to put it together and get it working, even designed and made a drive circuit and isolated power supply that can drive ~24w into each gate so I could use it with any IGBT imaginable, but never did anything w/it because I realized I have no use for it... I'm still a college student with $3000 to my name (and dropping...college...) so where am I gonna get the money to even get the solar panels and ~96s battery pack (probably would go for a Tesla M3 pack considering its the perfect voltage and almost $100/kwh here in the states)... Oh and a house to run with it...

TBH if in the future I ever actually get out of college and somehow find a job and not die of old age by then, going into this from a "have power no matter what" perspective, I'd probably use something like your Prius "mains" inverter and a 3-phase 208v to 240/120 ~45kva transformer (idk pricing in the EU but in the states they show up pretty cheap, Some guy near me is selling xformers near me for $5/kva).

Regardless, the idea is that with less than $1k you can have a very versatile DC-AC power inverting station, and being a Prius inverter, don't need a ~340vdc battery pack since you have a boost converter available, which if you assume can do 100A, is still 5kw @48v, and of course is super scaleable. In the end of the day it's thousands of dollars worth of power electronics that you can find in a nice little box for $100 or even less. Plus the time you'd save, no matter how nice the mosfets are, when they go boom it's not a swap and go scenario, most of the time the pcb itself blows traces. I wish they made super-high current MOSFET bricks like the IGBT bricks we have. I know there's some smaller ones but so prohibitively expensive.

And in an even worse shtf scenario you could run the prius boost directly off of solar w/o batteries, would probably need a decent capacitor bank for the HV bus but still.

I'm not really into magnetics and the sort, but from what I understand it seems like what makes inverters bulletproof is how much transformer is between them and the load. I guess the magnetic coupling also acts like a buffer and any load-side short is mostly tanked by the transformer inductance and by the time it reaches the inverter, its probably tripped the AC-side breaker. Whereas in "hybrid" inverters where you only have a minimal filtering inductor in between, all the short instantly reaches the IGBTs.

Probably why the ozinverter is so reliable, cause you have 20+kg of transformer isolation to "tank" any spikes and shorts before they get to the switches. Imagine how smooth a prius inverter and a 180kg transformer would run... Those Japanese electrons would give the sun itself a run for its money.

...did I mention I have a thing for off-grid inverters? :D
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Re: OzInverter Build

Post by GaryHo »

I have built my own inverter almost the same but with improvements such as Totem Pole Fet drivers. It has been running my house for the last 6 years. It is capable of 8KW continuous and can start a 5KW induction motor.

Re Prius inverters, they may be great at 300 VDC but the IGBTs are not so efficient at 48VDC.
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Re: OzInverter Build

Post by mackoffgrid »

I built my own inverter but something quite different. I have watched the OzInverter evolve since an Aussie engineer diagnosed the heavy standby current in an old Chinese inverter - name I have forgotten; then the modifications of the infamous Power Jack inverter which then led to the "Oz Inverter" design. I am now probably 2 years out of date, but there were 2 main versions of inverting, one using the chinese EGS8010 (I think) module and the other used an Arduino Nano module, which would be my preference. I think this was refered to the Nano OzInverter.

Many MOSFETs were killed in the evolution of the Oz inverter :D

Various builds had differing results in regards to MOSFETs blowing up.
I agree with Gary re: totem Pole drivers.
I prefer to go one further and use isolated gate drivers.

One of the better results I can remember is by a guy in Queensland that used a "Big Ass" E transformer he acquired from a junkyard.
If you want efficiency, go with a Toroid, but if you want a more forgiving transformer with a better sine wave output, go with a "Big Ass" E core transformer. An E-core transformer is much easier to wind as well.
meCAN : Dual / Trio CAN Arduino Library for stm32F103/5/7 , F412... , L452
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