Output voltage adjustment

[dochubert]

While re-reading some posts, came across Lighthunter's test of adding a resistor to the resistor stack on the control card.

I want to update info i wrote in post 186 page 13 regarding powerjack.
AC output volt increase. I had stated that cutting trace between R262and R259 and placing
A 470k resistor across the 2 points would result in 5v output increase.
Good news is it does raise v but the bad news is that it makes voltage regulation unstable.
I cant really explain definites but i have seen voltage drift from 118 to 113 without a reason implyingbattery voltage didnt change and load current didnt change during vout drift.There does seem to be less tight voltage regulation with load changes and with batt voltage change as well.

All in all, if you need to change output voltage of PJ inverter, there might be a better way.

Lighthunter,
I've been thinking about this one for awhile, and wondered if you had ever found a definitive way to adjust output voltage.  It seems, at least for use in the states, that all the powerjacks have a bit low output voltage.  My 48v split phase unit puts out about 114v that pulls down another 2 or 3 volts under more load.  The TVs, lights, and the fridge don't seem to care too much but the microwave hates it.  It runs and seems to work ok, but sounds like its in pain.
Anyway, I'd like to get that output up closer to the 120v the grid provides (and quiet that microwave!)
Your idea above seemed to work but you noted that it made things unstable.  Did you try any variations?  Did the added resistor get hot?
Anyone else have any success with adjusting up the output?

While staring blankly at the picture of the resistor added in as Lighthunter tried, a thought hit that maybe the instability he experienced was from the small lead size of the added resistor compared to the relative size of the current path provided by the resistor stack.  It did seem to accomplish the goal, just not reliably.  Possibly a higher wattage resistor, or even a surface mount soldered heavily across the ends of 259 and 262, so there was no "weak point" in the stack, just an increase of stack resistance.

Why a resistor stack anyway?  Why not just one or two resistors of appropriate value to the task?  Spread the heat load?  Cheaper?
The more I learn about these things, the more I realize how little I know. 
Well, maybe this has all been explored and discussed and I just haven't found the right post topic yet.  If so someone please kindly point me to it.
Thanks for a great forum
dochubert

[lighthunter]

dochubert! its been awhile since I,ve heard from you,
obviously, i missed this post from you.

Yes! the additional transformer on output feeding back an
adjusted voltage to the PJ control works flawlessly.
In my setup the PJ is outputing to two separate toroids primaries.
with series secondaries  producing 240v. The external transformer.
then is connected across the 240v and feeds back on an isolated.
winding the 110v the pj control needs, to be in balance. This mod
does cause the pj control to drive primaries 1 volt higher than original.
design. In some cases with low battery voltage it could cause a problem.
in my case i went to lithium bats which jumped me up to 25-26v under.
load vs 23-24 lead acid giving headroom for the output voltage change.
If you arent using a grid tie inverter connection though it may not ever.
be a problem.  This one is always right around 239 now and the 120 outlets.
are so close i cant tell when they are on grid vs inverter by measuring voltage.
117-120 and the 117 onlyhappens under light load usually 120 under heavy load.

Please feel free to ask questions if i can help!

(one more thing, this mod would interfere with battery charging.
feature which i dont use per Oztules advice so it isnt a problem.
if need bat charger then im sure there is a solution, i just didnt.
worry about it.

cheers LH

[dochubert]

Hi lighthunter,
 I haven't been posting much lately; little to report, and busy getting the house ready to sell.  But interesting timing on your reply here, as I just recently tried the 470k resistor idea of yours.  Unfortunately, I got the same results you got.  Voltage is up to where I want it (120/240), just not reliable regulation.  It drifts all around from 120 to 116.  The microwave is happier, and nothing else seems to mind the drifting, but I don't think I can live with that instability when I go fulltime offgrid.  I used a surface mount resistor soldered heavily across the ends of the two existing resistors to minimize any chance of a weak current path, but it made no difference.

I'm going to start to look for a transformer to try your better solution.  As I understand it, I want a secondary output that is 2-3 volts less than what the pj is actually outputting to fool it into raising the pj output by the 2-3 volts difference.  Right?
Oh, and I don't have any plans at all to use the battery charging mode of the powerjack, so that won't be an issue for me either.
Thanks for the reply, and I have no doubt that I will have a question or two when I get started on the transformer mod, so thanks in advance!

[lighthunter]

Hi Dochubert!

Quote (It drifts all around from 120 to 116.)

Thats not too bad... i left mine that way for quite a spell, defenitely better.
than the low voltage. My grid tie was the main one that complained about it.
It is odd behavior though and certainly not ideal.

Quote
 (As I understand it, I want a secondary output that is 2-3 volts less than what the pj is actually outputting to fool it into raising the pj output by the 2-3 volts difference. Right?)

Correct. I like to test the transformer by wiring a plug in cord to the winding and.
plug it in to 120 or 220, the voltage you desire, and measure the output winding
to verify it outputs whatever the pj control board measures now before modification.
This way you get to see the results before you make changes.  Its easier to find xfmrs with.
multiple windings and add/subtract them together than to find a transformer with the
precise value u need. Also dont be afraid to try heavier transformers. They can cost less.
watts to idle than a small one. Also E-cores can be good. Generally, i agree that toroidal.
ones are more efficient but efficient EI cores also exist. Example, I have a 8KW 200lb.
unit from a scrapped ups that scarcely uses 40 watts to run. Ive found computer equipment
transformers to be the best. The one I am using for this purpose is about 15lbs and it takes
5watts to idle. Its cold to the touch after on all day. Generally battery charger xfmrs are power hogs on the other hand.

Blessings to you & family, hope moving goes smoothly! 


LH

[dochubert]

Hi lighthunter, and thanks for the info.  Haven't picked a transformer yet, but soon....

Some interesting observations;
On another thread I showed my temperature controls setup.  One sensor on the mainboard heatsink and another on the first coil nearest the power switch end of the powerjack.  With these controls, and partially why I chose this particular control card, is constant temperature readout.  So I can now see exactly what temp the heatsink and first coil are running at and adjust the fan control accordingly.
What does this have to do with output voltage control?

Turns out the modification of adding the 470k ohm resistor to the resistor stack has changed the range of voltage drop across r14. The same r14 I have been trying to determine a proper value for in determining the high battery voltage trip point. Unintended consequences.
So, the added 470k resistor moved the range about 3 volts lower, which works against me, making the unit trip at lower battery voltage.  Luckily, I don't plan to use this mod for long, opting for the transformer method discussed above.
 
Also, I noticed that heatsink temperature affects the voltage drop across the R14 resistor on the control board. As heatsink temp rises, so does the voltage drop across r14, meaning its bringing the pj closer to a trip off with higher temps.  When the fan kicks on I can watch the voltage drop decrease right along with the temp decrease.  Presumably, my temp controls will prevent heatsink temp from rising enough (with the 470k mod removed) to cause tripoffs, but its troubling just the same.  I lowered the setoint a couple degrees to turn the fan on sooner in the meantime, because I want to observe for a few more days before changing it.  (and don't have a suitable transformer yet anyway)
One idea is to remove the original heatsink sensor from the heatsink and maybe stick it to the inside of the clamshell.  My independent control will be turning on the fan anyway, and the control board will be happy thinking the heatsink is running nice and cool, and it won't be affecting the high voltage trip point any significant amount anymore.  Sounds good. Might try that one....

[dochubert]

I spent some time last evening looking at transformers on ebay.  Not too good for choices there, but was hoping to go cheap, and not too sure what I want at this point.  Lighthunter, your control board on your powerjack is obviously a 110v type, while mine is 230v.  That seems to be limiting my choices, at least with cheap stuff from ebay.  I am going to need a xfmr that inputs 230v and outputs about 220v to make my pj output ~240v.  I wish I was an accomplished transformer winding expert like Oztules, then I'd just custom wind what I need.

Lighthunter, have you used a clamp on ammeter to read current in your transformer secondary going to the maint connections?
Maybe this is a dumb idea and I'm missing something, but if the maint circuit of the pj doesn't use too much current, couldn't we just insert a resistor instead of the transformer between the output connections and the maint connections?  Not sure what value to use to drop voltage 10v or so, but I'm not seeing why that wouldn't work.  It might affect the load control aspect of the maint circuit some, but wouldn't think too much if the ohms value isn't too high.  If you think it might work, I would love to hear your best guess for resistance value to use.
I'd appreciate your (or anybody else's) thoughts on this

[dochubert]

Well, assuming the resistor idea isn't feasible, (and I guess it's not since nobody chimed in with "Gee, why didn't I think of that?), I went to the local industrial surplus house this morning and didn't find any multi tap transformers of suitable specs, but did find a 115v to 230v step up unit fairly cheap. Wanted a 230v input, but this will do I suppose. Brought it home and found its output is already 6 volts higher than even with the pj output.  Couldn't be lower, of course.  That would have helped.   
(Murphy is never far from my side)
Anyway, started taking it apart.  Have begun unwinding secondary turns. Winding mods always seemed too much for me, so avoided that sort of thing, but I guess I can handle this one.  Figured I would start with 5 turns removed and see what my output is then.  Also, before I get to testing I have to put the unmodified control board back in the pj.
Have company coming soon so have to quit till later, so thought I'd get a quick update in here.

[oztules]

Measure the difference that 5 turns makes, to get an idea of turns/volt or volts per turn etc... then you know how much to remove or add to get whatever you want.

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

[lighthunter]

Dochubert,
Quote:

"have you used a clamp on ammeter to read current in your transformer secondary going to the maint connections? Maybe this is a dumb idea and I'm missing something, but if the maint circuit of the pj doesn't use too much current, couldn't we just insert a resistor instead of the transformer between the output connections and the maint connections? Not sure what value to use to drop voltage 10v or so, but I'm not seeing why that wouldn't work. It might affect the load control aspect of the maint circuit some, but wouldn't think too much if the ohms value isn't too high. If you think it might work, I would love to hear your best guess for resistance value to use. I'd appreciate your (or anybody else's) thoughts on this."

I have not measured the current as you say and I would expect it to be milliamps ,undetectable with hall effect clamp meter. Just to clarify, how I see what you are describing. (measure the current between lead wires to maintx and maintx onboard terminal.) As long as battery charging
is not going on, then that current would only be enough to supply the sense feedback circuit on pj control board. I dont see any good reasons why it wouldnt work to add a resistance. Basically using a voltage divider. I do think it would work i have no idea how well though. voltage references with series resistance and current flow generally tend to be spongy in response to change but it may work better than i think. I will play with the idea when i get a chance. Sounds like you have something going with a transformer and that will get you the "stiff" control you want no surprises.

I only isolated one of the onboard AC connections for this mod, the other I left as it was originally connected.  If you need more detail on connections just yell. I will try to watch this thread closer.

Thanks for winding info and grid tie info oztules!

LH

[dochubert]

Thanks Oztules and lighthunter,
Probably be tomorrow afternoon before I get back to it, but yeah, I figured 5 turns would tell me how much more to take off to get output down to 220v.  Glad to hear I'm on the right track.
Lighthunter, the reason I asked about current was to verify my own guess that it would be minimal.  That means almost any wattage transformer would do the job of sending a signal to the maint connections, which means future versions could possibly be small enough to tuck into the pj case.  The one I bought today definitely won't be in the case. 
The resistor idea should drop the voltage (with the correct value resistance - no idea what resistance to try) and with minimal current flow shouldn't be a problem to the circuit, BUT
Doesn't the maint circuit of the control board also have to do with load control?  I'd be afraid adding resistance there might change the range of control or something like adding resistance to the resistor stack changed the hi battery voltage trip point.  Unintended consequences.  The transformer is a better solution electrically speaking, just not as easy to do and bulkier.  Oh, and I planned to float both of the original sets of leads originally connected to the maint connections and just connect the new transformer's secondary.  Seemed safer that way.

[lighthunter]

  That means almost any wattage transformer would do the job of sending a signal to the maint connections,

Seems like the first transformer i had tried was 10w or so.  It worked ok and i used it
that way for a long time it ran quite warm. One day i noticed a bad smell and recognized
It as hot/fried circuitry, immediately took case apart to find it was the small transformer.
That was one of the reasons i went with external xfmr. That could have been caused by the xfmr itself though ...shorted turn etc. I really didnt look for detail why i just got rid of it.

Using transformer to change feedback voltage won't affect battery over/under volt at all. Ive never changed my battery v trip point and it still reliably works at 30. Very puzzling the other resistor change affected that??
Power control (over current)   **edit** (removed error, explained in next post). This mod defenitely will remove power control unless current through the metal ct can be maintained while only affecting voltage. Might be a few ways to do that. Proper fuse size will help until then. I would try to keep (phase relation/polarity) on maintx terminals same as original design just in case it matters...   
Only undesireable result i had was my kwh meter runs backward. I dont think that had anything to do with this mod tho because both my pjs do it and i didnt change voltage in the other. Maybe its as simple as flipping the ct the other direction. I never use that kwh meter anyway so no big deal but u might want to keep an eye on yours just in case.

Have fun!
LH

[oztules]

"Power control (over current) from Oztules comments is done by ct (small black donut around one of the maintx leads). "
NO...the little black donut CT is for the power meter on the front panel.

The little steel transformer on the mother board is the CT that the unit uses for current control purposes.

I have not noticed too much drift on my units, but my transformers are much bigger and stiffer too... but usually a 5-10% variance in voltage should make little difference to your appliances.

The grid usually moves by 5 -7% during the day too... sometimes by as much as 17v locally, particularly if you have grid ties in the area on a sunny day. ( 240v grid).

Look for soiling or similar on the rear of the mother board, perhaps that is interfering with the very high impedance staircase for voltage stability.

 Mine holds at 240-241v under all normal loads. It is a standard PJ 15kw set with the 5v6 zener on the O/V resistor. Only if the grid tie is operating with it does the voltage rise, and then up to 255-257 and the grid tie shuts off anyway.... and we are back to 240v again.


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

[dochubert]

lighthunter,
Yes the 470k resistor mod definitely changed the hi battery voltage trip setpoint.  Temperature of the mainboard heatsink affects it too.  Or, more precisely, the signal sent by the temp sensor affects that trip setpoint.  I probably wouldn't have realized it if I hadn't installed leads for continuous reading of the voltage drop across r14 and independent fan control that includes continuous temp reading.  While battery voltage was staying relatively constant floating at about 57.5, and with the pj under only a light load (my freezer) at about 150 watts I could watch heatsink temp go up or down and r14 voltage drop changed right along with it. The resistor mod moved the setpoint lower and then when the heatsink temp took it down more that was enough to trip the pj offline, even with running a 5 meg resistor for r14.  My testing indicates that the 5 meg resistor (without the 470k resistor mod) puts the setpoint about 68v, although I can't say for certain since I'm not willing to run my batteries up that high to cause a trip.  Based on r14 voltage drop readings it should be right about 68v. The phantom factor, or those mysterious mid day tripoffs might just be a result of conditions of full batteries and full sun still wanting to charge them, with a hot day thrown in all contributing to heatsink temperature increases that pushes down the setpoint and results in a trip.   Although I haven't done it yet, I intend to remove the original heatsink sensor from the heatsink, but leave it plugged into the control card and see what happens.  Don't need it to protect the system anyway since my independent fan control works very well and reliably. If the phantom trips go away, problem solved.  If not, there's always the zener diode.

But, this post is about output voltage, so back to that;
First operational test failed.
After a bit of cussing and frustration, got enough turns off of the secondary of my transformer to get its output down to about 222v.  Planned to start high as I can always take some more turns off, but putting them back on is a bit more difficult.  Removed and floated all connections to the maint N and maint X connection points and then connected the secondary of the transformer to the maint N and X connections on the control board.  Lighthunter, I know you left the maint N connection connected, and that's probably where I went wrong, but it worried me that with your hookup, there was a direct connection between the primary and secondary of your transformer.  I guess it needs it.
When I turned on the powerjack it hummed loudly and the power meter lit and then said 356v.  There was never an output to receptacles (no loads connected anyway) or the new transformer, so the pj had no feedback and didn't actually start to output.  I shut it off before more than a few seconds had passed to prevent frying anything hopefully.  Tried it a second time with same results.  Decided to think about it awhile before trying anything else.
I suppose next would be trying it with the maint N connections restored to normal as you did it.
Possibly, the 115v to 230v transformer is the problem, but don't see why that would matter, but maybe it would....  it connects to the neutral (toroid center tap) instead of the other 230v leg.  Still shouldn't matter....  If that's the problem, I'll have to find a different transformer and start over
Your statement;

Only undesireable result i had was my kwh meter runs backward

has me puzzled.  Are you talking about the meter on the powerjack or something external?  analog meter?

[dochubert]

Been thinking about it for awhile, and its got to be that I unhooked the connections from the maint N connection point.  So shot myself in the foot.  (Should have just followed the directions)
Maint N and P4, which is L1, are the same point in the circuit.  They have to connect for feedback to work.  The L2 side is maint X separated by the transformer, which does the comparing for voltage control, which is why this mod works in the first place. 
Seems to make sense, anyway.  Still wonder about the primary and secondary having common connection on the L1 side, but if the pj doesn't mind, why should I? 
The only question then is whether it makes any difference that the primary of my transformer is connected to L1 and neutral (center tap of toroid) instead of L2.  Guess we'll find out tomorrow in the second operational test.  If it does matter then I have to switch to a 230/230 transformer and start over

[lighthunter]

Hi Doc Hubert!

Yeah i thought about the 120 vs 240 version difference. It shouldnt matter unless they were monitoring the 220v to the maintx terminals. Quick verification, put all leads back where they were b4 you started and turn pj on. Verify output voltage is correct. Then place ac voltmeter on maintx terminals and measure. If this voltage on board terminals measures 220 then you need to keep that voltage (near 220). You may or may not need a different transformer. I suspect the original design brings in 220v to the board, if so, switch the windings around.

1.Start by leaving everything connected as original verify normal operation then power off.

2. jumper connect 120v winding to the 120v leads that go to a 120v outlet or cut cord off a discarded appliance and drive the 120(low volt wdg of your xfmr) then jumper(connect) only one of the 220(high voltt) wdg to maintx-N. Leave the 2nd lead disconnected from anything.
 
3 now power it up. Measure with ac voltmeter between both of the 220v xfmr leads, hopefully it will read 210v. Now measure between the unconnected lead of your new xfmr and maintx-L this voltage should be less than 10v AC, if it measures like 210 or 250 then power off and swap the two leads of your new transformer. Now power up again and verify only a small volt difference. Ideally if your voltage was 224 between maintx N-L, you will want maybe 208.  That will cause feedback to increase output to target 224 again and add 16v to the highv winding 224+16=240v which will bring 110 output to 120v,

After verifying this, then shut power off and rewire the 120v side of your new xfmr to a permanent location near pj transformer, not outlets because if fuse blows you would loose feedback. Then connect the 240 or should i say 208 side of your xfmr to maintx-N and maintx-L. Of course remove all terminals that were on each and bolt wires together creating two separate maintx terminals that do not touch the board. you can float 1 or both of them its up to you, i mainly just did one because i only had 1 bolt small enough to go through those rings and it makes it neater to leave maintxN original. Im not sure theres any benefit in floating the second lead.

Sounds like u will be fine though, you almost had it. Im wondering thougb didnt u say you had an original turns ratio of 120 to 208? I think that would hav been perfect unmodified. Better test and see first, maybe its perfect right now. I'm thinking you dont want higher than 120/240 output as you will drive up idle current and reduce headroom for battery voltage sag. Then you will have to alter turns ratio of the toroids. I'm with you though the 109-112v was just too low. I had trouble with that when i had it out at the solar panel and ran 100' wire to the load center in basement then by the time it got to the garage where freezer is . I have since with oztules advice acquired an awesome 3.5kwgrid inverter that can do 400v mppt and put in basement so i dont loose with long cable run. Next to load center the 112v wasnt a problem and wouldnt have increased mine but i couldnt adjust parameters of my grid tie and wanted to run voltage centered between 120v parameter which was 107-130 (dont know why UL1741 makes em monitor the 120 when its supposed to feed on L1-L2

Back to your situation, I think you just about have it whipped, the power meter i mentioned is the one on the pj faceplate, it does this by the phase angle of power factor and the current transformer, somehow I inverted it? Maybe i switched the toroidal transformer leads and its reading a negative power factor instead of positive one? i will figure it out, thats why i wanted you to be sure to keep polarity of lead wires original. 

Regarding the power control, i havent corrected mine but did have a look at the board and the metal current transformer. Looks like i could desolder current transformer from board and mount it on a new board which would allow isolation while leaving secondary side connected to control board. This should restore normal power control including fans. I was wondering why my fans.
never came on anymore. Kind of missed it. I ender up doing my own cooling thing like everybody else. I couldnt complain about fan control on this one, before i bypassed current control it used to come on low speed then faster and a high speed when it went over 2kw. I have no toroids in the box anymore and the fet sinks barely get warm to touch running 1.5-2k all day

CheersLH