Author Topic: My 12kW powerjack build - Ozinverter Inspiration!  (Read 24249 times)

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Offline influence

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My 12kW powerjack build - Ozinverter Inspiration!
« on: June 23, 2017, 09:36:10 pm »
Hi all

Well done as always to ozules for laying the groundwork for the powerjack builds....

I finally received my custom toroidal core.....dimensions: 230mm diameter, 100mm hole, 210mm tall...
Weight has not been measured accurately but is estimated at over 50kg bare...

I will document my journey here to produce a 12kW inverter using the 15kW powerjack MOS and controller boards.


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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #1 on: June 23, 2017, 09:37:54 pm »
First step was to clean, grind the edges.

Then I coated it with a potting compound epoxy...

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #2 on: June 23, 2017, 09:40:26 pm »
Then I wrapped it with Kapton tape...and then with mylar film.
I *really* don't want the core to ever be conductive....

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #3 on: June 23, 2017, 09:45:15 pm »
My calculations

Many thanks to oztules "rule" of 2800sqmm/volt as the core basis for 1V/turn

Based on my core, the core cross sectional area is 210 x 65 = 13650mm2

So we take 13650 / 2800 = 4.875V / turn !!!

Gotta love this method of using huge cores to reduce turn requirements...

So going with a ratio of 1:8 (30V : 240V)

I ended up using a ratio of 6 turns of the primary : 48  turns of the secondary.

I decided to use what I had lying around (orange 4+E cabling).

So I set the primary coil gauge to 3 lots of 25mm2 olex 90C cable and
for the secondary 1 lot of 16mm2 olex 90C cable.

Based on the above, I would require:
3 lengths of 25mm2 cable - 3.8m-4.0m each
1 length of 16mm2 cable - 28m long

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #4 on: June 23, 2017, 09:49:56 pm »
So I wind the secondary first....

Boy this was a bugger to wind...lucky I was on carpet tiles....

But seriously sore afterwards!!

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #5 on: June 23, 2017, 09:52:57 pm »
So after the secondary is wound. Lets check 1 turn on this transformer to see if we are within our specs...

Using the lightbulb dropper method. Basically as described in other topics, you take a 240v lightbulb and put it in
series with the secondary winding....you wire a switch over the bulb terminals to allow you to short the bulb after
its lit. I then wound 1 turn as a primary...to measure the 1 turn voltage...and voila we have over 5V on the one turn...

Im happy...lets wind the primary next!

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #6 on: June 23, 2017, 09:56:05 pm »
Ok primary winding time! Now if I reckon I was sore winding the secondary...guess again...
I was seriously buggered after winding 3 lots of 25mm2 together....

3 lots in parallel gives you 75mm2 effective cross section..but with slightly better heat dissipation.

See the RP7 regular sized can as a reference to size of this monster :)

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #7 on: June 23, 2017, 09:58:57 pm »
Now lets check the outputs...

Im happy with 29.5V ...this means it will work quite well at lower battery voltages...

My battery banks are 2000Ah each...so a total of 4000Ah is available to this monster.

Stay tuned. I will be assembling the noise filter choke next....

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #8 on: June 23, 2017, 10:01:05 pm »
Bigger than any I have wound thus far. As you have plenty of room, it would not be a bad thing to add a few more turns to the primary, and so get even further than the saturation point. This will help get iron losses down further before you use the inductor.

That thing is huge.

.......oztules
Flinders Island...... Australia

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #9 on: June 23, 2017, 10:07:30 pm »
Unfortunately two reasons I cannot wind more...one there is no more room and two it would raise the primary another 5V if I wind one more turn...

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #10 on: June 23, 2017, 10:11:02 pm »
Perhaps I can remove a turn or two from the secondary to reduce the ratio?

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #11 on: June 23, 2017, 11:57:06 pm »
Sorry, I meant the secondary.... not thinking straight. If we wind for say 260v not 240v, then only use 240v, we are using lower flux, so lower iron losses... so more on the primary and secondary equally ( by ratio that is )

......oztules
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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #12 on: June 24, 2017, 04:28:47 am »
Ok noted. Btw does it matter which side of the primary the choke is on?

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #13 on: June 24, 2017, 05:03:33 am »
No...


..........oztules
Flinders Island...... Australia

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Re: My 12kW powerjack build - Ozinverter Inspiration!
« Reply #14 on: June 25, 2017, 01:32:36 am »
Had a seriously productive weekend...

I have used a ferrite transformer calculator and figured out the suitable turns for my choke (18 - 20 uH).
I ended up using an E70 N27 core from RS.

I did a calc for the 3.5 turns it came to about 0.5mm gap
However at 70mm2 cable I cannot fit 3.5 turns.

So I went with 0.2mm gap with 2.5 turns. It *just* fit.