Author Topic: Building a 6kw pure sine wave inverter using power jack boards part1 transformer  (Read 24934 times)

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Offline oztules

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Worth a shot. If you have a lathe handy, it will be easy of you can get the steel to unroll form one former to the next, tension from a bearing bar will make it pretty tight wrapped. I expect the steel to be fine.

The funny thing is, as we make the hole bigger, the same amount of steel will have much less cross section, so a few cores will be needed... but at that price. nothing to loose.....everything to gain.

As CT's they would have to be fairly decent, or the eddy currents would skew the figures a lot more than needed.... maybe... possibly....


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

Offline steve3

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Hi Oztules I don't know if this is the right place to put this but its the only way I can get some info from you. The last time I talked to you was to tell about the inverter on light on 24/7 remember. I got on to power jacks and waited a long time what with the holiday in China in February, In the end They said I needed a full set of boards this will most likely cure the trouble for £100.00, was this a good deal ??, as it took so long to come in the end I traced the fault to the control board with the three leds on, the problem was very bad soldering shorting out the control transistor, ah well live and learn.

I'm now trying to run off grid and am having trouble with over voltage tripping out the PJ as the sun get a bit higher in the sky, hoping you can come up with a method of controlling this, thanks if you can.

Do you remember we were doing tests on my 8000 PJ, we put a link wire in one of the plug tops linking out n to earth as my sonny boy inverter would not start, I have since modified this with a 1100 ohm resistor, this seems to stop the E Trip going out at times. Thank for all your help M8y, Steve.

Offline oztules

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What I do...

There is a resistor near the main chip. It has the words cut if high (Ithink) will check again later today ... anyway it is a normal 1/4w resistor through hole... of a few megs from memory.

I use a 5v6 zener in parallel with this resistor, as it is just a piggyback and easy to do.
Picture of the resistor is here #59 http://www.anotherpower.com/board/index.php/topic,902.45.html

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

Offline steve3

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Hi Oztules that sounds a simple mod, just a couple of points,( should the resistor and the zener diode be changed)  ( is the diode looking down towards the big chip. How do you find out all this stuff M8y. Many thanks. Steve.

Offline oztules

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Hectic here at the moment steve... sorry...

I just piggyback the zenner across the resistor. No reason to try to get it out of the double sided board amongst those fine tracks.. nothing to gain really. It is a 10meg resistor on this board



I find it out because I need to .... mother of invention

I expect it cripples the voltage sense for charging with the unit unattended.... but I don't use that function, so never bothered to find out... lazy...

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

Offline steve3

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Hi Oz I've said it before and I will say it again, your a Hero and a Gentleman, that's a much better picture for my old eyes, will let you know how it works, many thanks, Steve.

Offline steve3

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Hi Oz It was hard to find a 5.6v zener as it was a holiday over here, but in the crap box I found one, popped it in, things seemed more stable when off grid charging, as the batteries came up so did the voltage, when it got to 31v the PJ made a bleep, the voltage went up more to 32.3 at which point I lost my nerve and switched off, was this mod supposed to stop things going over the top ?, any more help John, If you can crack this one for me I can stay off the grid a lot more, and that the hole aim of things isn't it, many thanks M8y. Steve.

Offline oztules

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No. This mod ONLY stops the PJ from turning the power system off when ever it gets nearly charged from an external pwm or mppt controller charging the batteries.

It does not have any effect on the charging of the batteries by whatever method you choose.... and it will render the internal charging by the pj itself as dumb, not intelligent.

If you use the PJ as a charger, this is not for you. ( and it would not have caused any trouble anyway without the mod)

If you are charging from some other source ( what I thought you did ) it will have no effect on charging, but will stop the annoying OV shut down.... I note that the latest board I bought has no bad effects at this time, and requires no fix... good to see.

If you explain exactly what and how your charging with, we can help.

From your comments thus far, I suspect it is using a grid connect inverter, reverse charging.

This brings it's own set of problems to deal with, and the PJ has no part in this.... ie you don't want the PJ to turn off... just to turn off the grid tie inverter.

So the zenner stops the PJ from turning off under any circumstances... what we need for uninterrupted power, but we must control the over voltage some other way.
If using a grid tie, then you need a voltage switch to shut the grid tie off when V= whatever you are comfortable with... 29v@7 amps perhaps.... but you can't expect the PJ to do this for you.... even a windmill style dump load wold be fine.

As a generality, the grid tie will shut off from over voltage AC when the batteries can take no more, and shut themselves down. For flooded cells this can work ok. This is because when the batteries can take no more heavy current, the power from the grid tie must go somewhere..... so it pushes up the AC voltage... and when it gets to ( whatever your design rules say), it will shut off... primitive but works with properly programmed and islanded inverters. The european ones fail this regularly, so are probably going to cause problems, the chinese ones seem to follow the rules more carefully.. SMA will cause all sorts of problems in this way..

So your best to make up your own OV switch, that interrupts the grid tie by battery voltage relay ( op amp and a relay).... or a very large dump load.

Before it sounds like you were relying on the pj turning off.... which is a no no.... if your relying on it to drive the house at all.... so you don't want to be doing it that way .

If you don't care if it turns off, then remove the zenner.... then the PJ will act as a voltage switch... but it will be useless as a steady load provider.... always something.... but it is not PJ's problem really, and needs another solution from the start.


It is interesting that the PJ could still see the 31v as too high, but now does not act on that information... interesting... maybe you could use that as the voltage switch signal????... ie any time it beeps, shut down grid tie relay.... ...... not so silly now I think about it,,,,


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

Offline steve3

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Hi Oz thanks for taking the time to sort things out for me, normally I run on the grid and use PV power via a big battery charger to fill up the batteries. When I run off grid which I like very much, The PJ as you know turns on the Sonny boy inverter in the loft, I then charge through the PJ which is very good way of charging Im not going through so many things not so many losses, I'm thinking the way to go maybe, your mod with the zenner moves the tripping point higher I'm thinking, If you could move the tripping point lower to say 29.6v (my top charging voltage), maybe make it more stable switching ?, using this tripping point maybe it could be done without relays, When it gets to the top level I don't mind it tripping out the system, I would then have to go back on the grid and finish charging.  Oz I will be guided by what you say is best. Steve.

Offline oztules

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You'll have to make your own bed to lie in here, as you have a problem of mismatching with no attenuator of any kind... only bang bang type results with what you currently have.

To make this work as you envisage, you would simply need to control the mppt point of the SMA, and all the problems would be gone.
SMA does this by varying the frequency a bit from the inverter to the grid tie inverter.. but they are matched ( and don't always play nicely either ):)

In your case, unless you want to make a voltage attenuating device between your panels and your grid tie, controlled bby the battery voltage, then I'm afraid you back to bang bang... unless you have a swimming pool handy that you want to heat up.

The swimming pool idea is the best, or even a few thousand liters of tank water. Then you simply use a 5kw water heater, and a triac control  ( 5kw light dimmer?? thing) controlled by the batt voltage, and you have a 5kw dump load. This would work seamlessly... but you need the "heat sink" available... ( a few in line water heaters from dud dish washers would do fine).
This would eb simple, and very effective to control batt V.

If you can't control the bottom end like that, then you need to control the input voltage/current to the grid tie  inverter... much more difficult, as it will need to be a 5kw pwm@up to 4-600v.

Those are the only real seamless ways I can see at the moment.

Other than that your in bang bang territory. If you don't mind power interruptions, then remove the zenner, and let the pj die, or use a comparator to shut down the grid tie via relay in the ac feed line from the grid tie to the inverter.

I don't see any other useful  way to do this, maybe Rossw or some of the other folks here have a thought on this.


.......oztules

Flinders Island...... Australia

Offline steve3

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Thanks for trying Oz, I will play and see if I can work something out, will let you know. Steve.

Offline rossw

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I don't see any other useful  way to do this, maybe Rossw or some of the other folks here have a thought on this.

Sorry, Oz, not much to offer here.
Unlike you (who threw brains at the problem), I was time-poor and threw dollars at it instead.
When I built, I had a Power Systems Australia RAPS5 inverter. It was expensive, but it did everything I needed out of the box.
When it let the magic smoke out 10 years later, I was deep in a hole and needed something seriously overnight. Again, rather than brains, I brute-forced it with dollars. A Selectronic SP PRO 481 is now doing the job (and doing it very well). http://www.selectronic.com.au/brochure/BR0007_03%20SP%20PRO%20Series%20II%20Data%20Sheet%20Web.pdf. It's far more expensive than using your brains and some effort, and if circumstances were different I may have done things differently, but they weren't.

So... after all the words, my comment is "I haven't played with the PJ and really am not qualified to make any suggestions!"

Offline oztules

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May I suggest you use the carcass and transformer from the first unit, and add a 15kw powerjack card and controller as a cheap backup unit.....and you get to play along too:)... http://www.ebay.com.au/itm/171760626915?_trksid=p2055119.m1438.l2649&var=470713282062&ssPageName=STRK%3AMEBIDX%3AIT

The $300 is not a fortune to avoid another hole.... make no mistake, the selectronics are very good units, but there have been early failures over here for them too.... Their back up is commendable, but comes at a time price.... particularly here...... (and when you start flying 50kg units around the place, it has a fiscal price too)

Then you will be able to compare them as well. I use a neighbors  selectronic as a comparison unit... you may be surprised at what these cheapies can do.

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

Offline frackers

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An interesting idea has come up - the cores I've found so far are not really big enough either with the size of the hole in the middle or the overall cross sectional area. How about rewinding the steel of the core itself and incorporating 2 of the 1" cores into one, starting with a larger inner diameter and then stacking 3 or 4 of these.

Still looking at this idea, fettled up the figures a bit having found a website calculator for winding stuff onto a roll. Punching in the inner and outer diameters of my 1" thick rings and an arbitrary thickness it comes out with a length of material required. Putting in that length figure times 2 and starting with a 90mm inner diameter I should end up with a ring with an outer diameter of 205mm. Stack 4 of them (i.e. material from 8 of the original rings) and I get a cross sectional area of ((205 - 90) / 2) * 102 = 5865sqmm and a weight of about 22kg. The material for the cores should be about NZ$20, the 10kg of 1.8mm wire was NZ$110 so only mylar tape and the primary to source now :)

Searching out an old trailer wheel hub and getting a CO2 bottle refill for the welder to make the winding jig.
 
Sounds to me as though a 6kw box isn't far away! Ah - got to find a box to put it all in!!

Robin Down Under (or are you Up Over!)

Offline oztules

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Now thats building a transformer... makes my effort seem a little less old school for sure....

Can't help but feel a lathe would do well in this application, rather than a wheel bearing arrangement... any one handy got one??

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