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Combining 2 8kw pj's into one new case for double the output...Possible?


Thatguydidit
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I have 2 Powerjack 8k LF Version 8 inverters. One popped when it was hooked to a/c charging circuit and it back fed the unit. My question is, can I combine the 2 coils and whatever necessary components from each in a new shell to make 1 larger, higher output inverter. And how would I go about that?  

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1 hour ago, Thatguydidit said:

I have 2 Powerjack 8k LF Version 8 inverters. One popped when it was hooked to a/c charging circuit and it back fed the unit. My question is, can I combine the 2 coils and whatever necessary components from each in a new shell to make 1 larger, higher output inverter. And how would I go about that?  

SORTA.

The only part you'll be able to "combine" would be the transformer itself.

OK, and maybe the mainboard (with the FETs on it) if your working inverter has 2 FET drive connectors on it (they're basically the same), sorta like PJ does with their bigger rated inverters.

Depends what parts you have.  Definitely can't use 2 control boards.

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Well, idea is to give me more capacity. Right now this 8k I'm running only gives me about 1300 on one leg before it goes into overload protect. Looking at the load imbalance it's typically only a few amps from l1 to l2. So if combining the coils will give me more load ability. I'm all about it...using it to power most of my house. Not overly heavy loads like microwaves or electric stoves. So loads typically fluctuate from l1 to l2 depending on what appliances are on

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2 hours ago, Thatguydidit said:

Well, idea is to give me more capacity. Right now this 8k I'm running only gives me about 1300 on one leg before it goes into overload protect. Looking at the load imbalance it's typically only a few amps from l1 to l2. So if combining the coils will give me more load ability. I'm all about it...using it to power most of my house. Not overly heavy loads like microwaves or electric stoves. So loads typically fluctuate from l1 to l2 depending on what appliances are on

So if it's going into OVERLOAD protect, that can be adjusted (depending on the control board version, there may be some DIP switches that set both the overload current + the charge current).  OVERHEAT protection is different, and much more common (especially at the loads you're running, i.e. 2.6kw)...which doubling the transformers should help.

You could technically just parallel the 2 transformers across each other.  WARNING: Make sure the transformer phases are the same, otherwise you're pretty much guaranteed to end up with blown FETs!  To make sure the phase is correct, you can parallel what I call the "primary" (FET sides, PJ calls it "O/P"), and then parallel connect ONE of the "secondary" (PJ "I/P) 3 leads together.  With the inverter running, use your DMM in AC volts to check across the other 2 pairs of leads, to verify that there is <5vAC difference between them.  (If you see 480v or 240v difference, the transformer phases are definitely opposing!  Swap either both of the "primary" wires, or try cross-color matching up "secondary" wires.)  Do NOT under any circumstance connect "parallel" wires that have a voltage potential between them, or you'll risk smoked FETs.

If you encounter issues or questions, post here, and we'll sort it out.

And remember that any experimentations are at your own risk 😉.  I can give pointers to accomplish what you might desire, but no guarantees come attached...

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20 minutes ago, Sid Genetry Solar said:

Well, idea is to give me more capacity.

You have the right idea.  The transformer size is the key to capacity.  If your two 8k units are identical, you should be ok to parallel the two transformers.  As Sid says, make very sure your phases are correct or you will blow things up.  You should be correct by matching colors of wires, but don't assume.  Test! 

You don't need the second mainboard/fets.  You don't need anything but the extra transformer.  If everything with the transformers paralleled goes as expected, the next step is to load it and see what happens.  If you still get an overload at too low a load value, there is something else you can try.  If your control board/output board has one of the 10 position dip switches (SW1) you may have to change some switch settings.  As there appears to be no key to setting these correctly, you will have to experiment.  The only thing known is that the higher the capacity of the inverter, the more of the switches are turned on.  With the inverter off, try turning on one additional switch, then test again.  Repeat until you get the capacity you should have, probably realistically you should be in the 3-4kw range, assuming you have enough cooling (very important!) for your transformers.  Remember that setting the overload trigger to a higher value does not necessarily mean you are not overloading the inverter, so don't go any higher than necessary.  Hopefully you have some way to monitor temperature of your transformer(s) because that is the real measure of your inverter's capacity.  It has to run the load, and it has to do it without overheating.  You will probably have to change to a high speed fan, or maybe add a second or third fan.  One thing leads to another!  Best of luck!

 

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If your two 8k units are identical, you should be ok to parallel the two transformers

 

I  read in another forum  you have a  powerjack inverter with 3 parallel transformers  you bought in 2013  that is still working .  Is this  true ?  Then you  will know how it is done  .    

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20 hours ago, dickson said:

I  read in another forum  you have a  powerjack inverter with 3 parallel transformers  you bought in 2013  that is still working

I have two 2015 model 48v 15kw powerjacks that have three 2kw transformers each all in parallel.  One still works and is currently running my house.  I consider it much more reliable than the newer models because the transformers were better quality and the control boards before version 4 were more reliable and stable than the newer versions.  Mainboards haven't changed too much.  I also have a third 15kw that has two 3kw transformers in parallel.  So yes I have proof that paralleling tranformers is possible and practical, provided the transformers are matched up very closely in all respects.  Three 2kw transformers in parallel are effectively equal to one 6kw transformer.  Yes, a 15kw powerjack is actually only a decent 6kw inverter, despite what their ads say.  An 8kw inverter is actually a 3 to 4kw inverter depending on what transformer they came with.

Powerjack is constantly changing their suppliers so the parts in any two given inverters might be different.  If Thatguydidit bought his two 8k inverters at close to the same time, there's a fair chance his two transformers will match up properly for paralleling.  He must be very careful in testing his transformers and his hookup to avoid loud noises and smoke.  Some of powerjack's transformers have balanced L1 and L2 phases and some are unbalanced.  My working 15kw has three unbalanced tranformers in parallel.  That is, it puts out 120v on L1 to neutral and 110v on L2 to neutral.  230v L1 to L2.  Needless to say, one could not parallel an unbalanced transformer with a balanced version.

My other 15kw inverter that currently needs a good control board has three balanced transformers.  When it was working, L1 to neutral and L2 to neutral are each 115v.  Still 230v L1 to L2.  The 230v output is due to pre-version 4 control boards which all output 230v and were not adjustable.  Later control board models dropped the output to 220v(why I don't know! - They should have increased output to 240v, not reduced it!).  I would be thrilled to find an undamaged version 3.6a 230v control board, or even a v2.8.  My two not-working inverters both had v2.2 control boards.  I'm not a good enough tech to repair them, hence Non-Working.  I'm always on the watch for an older 15kw multiple transformer inverter in good shape for sale.  I know there were many sold for years.  Where did they all go?

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21 hours ago, dickson said:

If your two 8k units are identical, you should be ok to parallel the two transformers

 

I  read in another forum  you have a  powerjack inverter with 3 parallel transformers  you bought in 2013  that is still working .  Is this  true ?  Then you  will know how it is done  .    

I think there must be another thatguydidit. The only other pj I ever got was a 3k in 2016. 

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I think there must be another thatguydidit. The only other pj I ever got was a 3k in 2016

 

Dochubert  was the other guy in another  forum .   Trying  to get 3 balanced transformer is like going down a rabbit hole .   Way too  expensive  replacing FETS .  It will be a lot cheaper to get a GS 12kw inverter   and  not have to  replace  FETS  just  testing  spare parts I  buy  on ebay .  One  bad  mosfet on one  mosboard  will destroy all the other mosfets and the LF driver and  sometime the control  board  and  the  fire from the exploding FETS  cause one of my mainboard to crack .    

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My other 15kw inverter that currently needs a good control board has three balanced transformers  post by dochubert .  

 

Whodunnit  is powerjack  in 2013 to 2015  with 3 transformers  .   Maybe Sean has a control board  from a donated inverter  but  probably  not working also .  Maybe  a new rev11.1  control board will work .  I  use a rev11.1  control board to replace rev10.3  and also work to replace rev 9.0  control board .   

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So I'm opening and getting started...looking at the 2 transformers they are dated a month apart, but wire color is different...am I to assume that the ferrite ring on both sets would be a safe way to assume input? The windings on the working transformer are black n red, with the red being the outside winding run through the ferrite. The transformer I want to wire in has black n yellow with the inside winding which is black run through the ferrite, so it's opposite

20210731_141952.jpg

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So the more "scientific" way to determine which is which would be the direction of the wire on the winding.  In this case, both black ones come off the top of the core, and the colored (red / yellow) come off the bottom of the core.  This should get the polarity forwards.

Then go ahead and power up the inverter.  Should run normally, if a bit louder due to the 2 transformers.

Then try connecting ONE of the "new" secondary wires to one of the "old" secondary wires: start with the red from the new transformer, red on the old transformer...

...measure from the other side of the secondary wires: black (secondary) on the new transformer to whatever the leftmost secondary lead of the old transformer is (black?) with AC volts.  Should be < ~5vAC.  If you get 480vAC, then the transformer phases are reversed; disconnect the one pair you connected together earlier, and this time try connecting Black (secondary) of new transformer to whatever the rightmost secondary of the old transformer is (red?)  Measure the opposing leads again...should be < 5vAC...

 

...obviously, at your own risk 😉.

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So, paralleled leg to neutral old, gives me 120.1 and paralleled leg to neutral new gives me 126.6.... secondary old to old neutral gives me 112.5 and secondary old to new neutral gives me 129.0.....new secondary to new neutral gives me 126.4 and new secondary to old neutral gives me 172.5

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1 hour ago, Thatguydidit said:

So, paralleled leg to neutral old, gives me 120.1 and paralleled leg to neutral new gives me 126.6.... secondary old to old neutral gives me 112.5 and secondary old to new neutral gives me 129.0.....new secondary to new neutral gives me 126.4 and new secondary to old neutral gives me 172.5

Those readings are not as important as the "neutral to neutral", "L1 to L1" and "L2 to L2" readings.  You want to know before you parallel the transformer secondaries together that they are a) the right phase, and b) not very far different voltage-wise. 

Reason being that if they're the wrong phase, you'll overload the inverter / blow FETs.  If they aren't very close voltagewise, there will be a much higher no-load current, and the transformers won't share load very well.

 

If you have the L2 lines as the parallel leg, there should be <5vAC across Old Neutral - New Neutral, and <5vAC across Old L1 - New L1.

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1 minute ago, Sid Genetry Solar said:

Might need to experiment shorting different "old" to "new" wires (only one at a time), and see if you can find a combination that gets the difference between neutral-neutral and L2 - L2 (or L1 - L1) <10v (let's say they aren't very matched!)

So maybe swap the primaries black and yellow to fix phase? Because when I ran left most old leg(red) to left most new leg(black) the other secondaries (L2 maybe?) showed 471.8 between them

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8 hours ago, Thatguydidit said:

Btw they say 16/17v to 230v

Ah, you have 24v inverters then.

9 hours ago, Thatguydidit said:

So maybe swap the primaries black and yellow to fix phase? Because when I ran left most old leg(red) to left most new leg(black) the other secondaries (L2 maybe?) showed 471.8 between them

If you found 471v, then the transformer phases are opposing each other...and one transformer primary polarity would need swapped.  Max voltage you should be able to find across the secondaries should be ~240vAC (give or take a few)...if you can find 480vAC, then they're definitely reversed.

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