PJ 8000 LF/SP Control Board Swap Issues

[sunnypower46]

Had a cold solder joint (I think) on my 24v control board (CB) near the fan end.  Flexing the board in that area would cause a loud buzz, very heavy current draw from the batteries then PJ alarm and AC output shutdown.  This unit has the new (2015) configuration single toroid.  Dr. Powerjack (Helen) sent a new replacement CB, which I installed OK (no thanks to red glue and hot glue globs).  The new CB had the two opto-isolators soldered onto the board, incidentally.

I didn't see any obvious bad solder joints on the defective board; but, it's tough to see with this surface mount stuff.  Maybe a cracked resistor?

So the issues?  The old board (when working) was producing about 233 volts, no load.  About 121-0-112.  The new board produces 239 volts, 125-0-114.

I've been following the posts re: upward voltage adjustment attempts.  I now find it interesting that changing out my CB has affected my output voltages significantly (somewhat to the better?).  As nothing else has been changed, it probably can all be attributed to board tolerances, I guess.

I'd like to find a way to balance the split phase outputs to approach 120-0-120.  Or at least I'd like to bring down the high side (only) a bit.  Instead of adding resistance to the "ladder chain", could I try reducing the overall resistance?  This board appears to have two series resistance chains on top and two on the underside -- maybe they all do as part of the H-bridge?  Without a schematic or block diagram, I'm shooting in the dark. 

Are the resistor chains providing feedback in each leg of the H-bridge?  How do I know which chains to modify?  Or is the voltage imbalance solely a function of the center tap on the toroid winding (being tapped off center)?  Perhaps I should be happy that I have close to the 240 volts that others lust for?

It seems odd that the CB circuit would be dependent on a circuit path that requires megaohms of resistance to control its operation.  That just begs problems, seems to me.

I'll finish up with a description of my small solar configuration.  I'm using microinverters (4) (APS YC-500A) with eight Solarworld 325W panels.  It all seems to play nicely with the PJ 8000 synced.  I route excess power to a 24v battery bank and use a Morningstar TS-60 PWM controller/dumper and big power resistors to limit the voltage and protect the batteries.

Each microinverter has dual inputs to separately support two panels.  I use a FET in switch mode to remotely switch the solar panel output off/on to each inverter input with a simple 12vdc (gate) signal.  A nice benefit of the APS micro (dual input, 250W+250W) is that it needs only one input active to establish sync.  The other input can be powered or not, but will instantly add/subtract 250W from the output via my "switch" without forcing a standard five minute restart wait.

I'm working on a automated shutoff/turn on of the solar panels to accommodate changing power demands.  This is done via the varying 0-24 vdc output to the dump resistors using a voltage comparator/latching relay circuit.  I want to be able to turn off/on some solar panels rather than just heat resistors, in a dynamic environment.  So far, it works nicely on the bench.  Need a few more pieces to bring it to the real world.  Currently, my eight human powered toggles switches do the job, but it takes up a lot of my time . . . . . . .

May have more to share later if anyone is interested.  For now, how do I get the high side (only) phase voltage down so I don't have potential issues with the microinverters?



 

[dochubert]

Hi sunnypower46,
Since your output was out of balance before the control board change, and still is after the change, seems likely it comes from the transformer.  You will need Oztules help with that.  He's the transformer expert.
It's interesting to me that your new control board is outputting nearly 240vac.  Maybe the powerjack people finally are getting output up where it should be?  It would be nice. 
Interesting also that the optos are soldered in on your new board.  Poor contact with the sockets has been an issue many here have dealt with.  Maybe you could post a pic of your new board?

I like your idea of switching on and off the solar panels instead of the gridtie inverters themselves.  Seems more efficient and eliminates the restart time for the gridtie.
Thanks and welcome to the forum

[sunnypower46]

Well, I think you are correct re: the center-tapped toroid.  I don't have much confidence a replacement transformer would have any tighter winding tolerance.  It's likely hit or miss.  I guess I'll live with it.  I put all my high wattage loads on the high voltage side to take advantage of the extra "oomph".  As long as the microinverters don't fuss, I don't think I'll hurt anything downstream.

I noticed today that when I ask for about 2KW from the PJ, the low side voltage strangely increases a few volts.  I wish I better understood the feedback loop path for voltage control.  The whole over/under voltage output variation from board to board can probably be traced to resistors with likely plus/minus 10% tolerance adding and subtracting in the "chain" total to produce an output voltage that will end up being higher or lower than designed.  And as I noted previously, my control board has four of these chains, all likely having tolerance issues.

The replacement control board seems identical to the original except for the two optos soldered onto the sub board.  Hope the attached pictures post OK.

My LCD display no longer shows correct volts.  I have no output on the secondary of the little transformer (solder points circled).  There's 240VAC on the primary pins, but I don't know what was designed for the secondary.  Probably some stepdown voltage that is scaled on the display board.  I'd like to send test voltage to the LCD display to see if it's input line is OK.  Any idea what voltage range would be safe to try?

[oztules]

The R249 staircase is the one controlling the voltage, the other ones control the syncing of the mains I think.... never looked too hard at those ones.

You rightly point out that is it amazingly high impedance's they are playing with, so it surprises me it does as well as it does.

Sounds like the voltage transformer is shot for the main screen.... try a volt or two and see what the scaling is.

Can't explain the two voltages on the split phase... I just can't believe they are winding them asymmetrical.
There will be a slight variation under heavy load, as the winding of one phase will be longer than the other, so copper losses will be greater in one than the other, but low and no load, should be the same.


.............oztules

[dochubert]

Thanks for the pics!
I noticed that the red and black wires from the add on board that controls the lcd display are reversed connected in your pics from mine, so would first try switching them before anything more drastic.  Especially if the lcd  worked previous to your board swap.  Red should connect to MaintxL and black to MaintxN.  Could be as simple as that.
Note:  Just the wires from the add on.  Your other wires appear to be connected correctly.  (Powerjack should have made it so the reds and blacks stay together, but they didn't)

Also, regarding the staircase, try thoroughly but carefully cleaning the areas in question including underside of the board.  If you are good with a soldering iron and you notice any weak solder points in the staircase, try beefing them up (heavier solder) a bit.  Again, carefully, as pretty delicate areas.  If not comfortable doing that, then don't try it.  Likely won't make any difference anyway.

[sunnypower46]

>Oz:  Thanks for weighing in.  I will experiment with the LCD display transformer in the next week.  Actually, I use two external displays with CT doughnuts on each hot leg to keep an eye on things.  But I would like to have the original working again.  If I knew what it was I could source one on ebay cheap.  If someone has a PJ open on the bench and could measure the secondary voltage, that would be helpful.

I'm not sure I follow your statement "the winding of one phase will be longer than the other".  Is this because the secondary is wrapped with multiple wire layers (duh) and the layer to layer cross sectional area changes?  They don't/can't account for this in the design/manufacture?  I was going to ask if it might be easy to just get in there and tap along "the single" layer until I found the voltage center.

>dochubert:  I'll be really (pleasantly) surprised if switching the primary leads of the transformer brings the display voltage line back to life.  Maybe it's a "special" transformer.  Unless I screwed up the labels I put on the wires before I switched things out, my board originally was red on red, black on black.
 
Regarding the staircase (resistor chain), I wasn't sure if you were addressing the replacement board or the original.  I think I'll accept the higher voltage on the current board, but I'll reheat some joints on the defective board at some later time and see if I get lucky.
 
>All:  PJ seems to have idle current under control in these new (2015) units.  When my solar panels go to sleep and PJ stays up late and on (Normal On), there's literally no draw from the battery bank (no loads attached).
 
Also, I haven't removed the big nut on top of the toroid.  Is the core open or potted?  If open, can't there be an alternate way to secure the toroid while allowing better airflow through the center?

[dochubert]

I'm getting 0.114vac on the secondary with 234vac on the primary

[oztules]

" "the winding of one phase will be longer than the other".  Is this because the secondary is wrapped with multiple wire layers (duh) and the layer to layer cross sectional area changes?  They don't/can't account for this in the design/manufacture?"

In a nut shell.... yes....... thats where the losses/differences are.

If they bifilar wind it, then no, but mostly they are multi-layered.

Bifilar ( two in hand) will give equal inductance and resistance, layer wound will be same inductance, but different copper losses---resistance.

I see the same voltage ... .114ac on the little tranny... who knew.... beats me how they are using it too.... seems an odd way to go about it.

Seems to be a single turn or so  only.


.................oztules

[rossw]

I see the same voltage ... .114ac on the little tranny... who knew.... beats me how they are using it too.... seems an odd way to go about it.

Seems to be a single turn or so  only.

If it's a *CT*, then the voltage is a function of the load resistor. It is really dangerous to run CTs unloaded!

[dochubert]

It sure seems sunnypower got the "Monday morning, crew hungover" powerjack.  First a flaky control board, then an unbalanced transformer, and now the lcd add-on card.  Only thing left is the mainboard and fan.
When I got a new control board from powerjack, I got the lcd addon too.  Guess he didn't.

Regarding the transformer, Oz, could he add a few turns to the low side secondary in an attempt to balance?  That seems a significant unbalance for any heavy use.

[oztules]

Ross, the tranny is across the 240vac, so not used as a CT, but as a very low voltage transformer. There is a separate CT for current measurement for the LCD.

I'm at a loss as to why they chose such a low sampling voltage to work with..... probably explains the poor results from the LCD output figures.

dochubert... yes torroids are very easy to add turns to..... Have not checked at all, but the cores look to be around the .7v/turn range, so say 6 turns on the low leg may yield a 4 volt difference etc etc.

[sunnypower46]

Turns out my display tranny is outputting around 0.121 vac, so in line with others.  I originally figured that low a voltage was just "noise".  I guess I was expecting something in the 5-20 volt range.  Thanks all for passing that along.  I'll try to squeeze a new LCD display out of them.  It would seem the problem lies therein.

I haven't yet removed the big nut securing the toroid, but I'm sensing from comments that it's open core.

So, in simple terms, if I can get to the hot end of the low side (HV) secondary winding, splice in and wrap a few turns of wire in the right direction, I'll pick up some volts?  Sounds easy enough for a temporary bench test. 

Of course, if this is doable, my overall secondary voltage will increase, too.  Be close to 250 vac, 125-0-125.  Then, I'm going to have to reduce resistance in the feedback chain, I guess.  That, at least, should increase system stability, if there's enough "adjustment room" in the loop. 

Perhaps this is the better way to increase secondary voltage for those needing it?

[dochubert]

I'm definitely not the transformer expert here, but seems to me you should take a few turns off the secondary hi side and add those same turns to the secondary low side...  Take 4-5 volts off high and add to low.  That should put you right on the money, both legs 120 and total at 240v.  No other changes needed.  What I don't know is how accessible that winding is for unwinding.  If the hi side is on top, probably ok. 
It almost seems like they put the center tap not quite in the center.  Too bad you can't just shift it a bit to balance the legs

[sunnypower46]

>dochubert:  I haven't peeked at the toroid winding yet.  If accessible and only one turn layer, I would just "re-center" the neutral tap.  Since my line to line voltage is good (239), no need to add or subtract turns in that case. 

Maybe Oz will enlighten us on the winding arrangement of these things.  If it's just one, maybe two winding layers on the secondary, it would be worth the shot.

I could poke at it with a needle and penetrate the enamel coating and check the voltage along the winding.  I'd be surprised if it's that easy, though.  Probably too many windings.

[dochubert]

Hope that works.  Could be easier than cutting some off one end and adding it back to the other.  If secondary windings aren't layered you might be able to count windings for the center and be within a turn or two of proper placing for tap.  Or just count from current tap 6 or 7 turns and try it there.