Power-One solar Inverter driving me NUTS!!!

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

I am suggesting following tests board installed and out of the chassis:
-> With the first board out of the chassis check the numbered GRP screw holes against a different one throughout the board. Probably most are open.
-> Measure the same thing installed in the board and you should have continuity on all GRP points.
->With the first board installed (but no wires connected) check the continuity between earth ground and the GRP plug on the back where the wire plugs in.
then go earth or GRP plug one by one over to the Boost1, Boost2, Bulk etc.

Once you figured out the grounding or GRP point situation, install the second board (with the big caps)into the chassis and don't hook any of the wires up.
-> earth ground to GRP plug on the second board. If they are connected, do:
-> earth or GRP plug to Boost1, then over to Boost 2, Bulk etc. one by one.

I know this is painful, but lets see what this does. Over all I say the problem is on the second board with the big capacitors ringing it at 1MOhm. That can't be right.

You are correct in that all of those grounding screws must be installed into the chassis for the ground to be continuous throughout. I did check for continuity between earth ground and all of the plugs that go to the second board and I found no continuity. Which is puzzling me because I don’t see any other ground points on that second board. Unless the screw in the center of the second board labeled “GP3“ is connected to ground through a center layer of the board.

I have both boards out right now. I will leave them out for a while, while I take a break to get my head straight and in case you need better photos or testing.. Then I will proceed with the tests you outlined above.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

I took several pictures at different angles of the bottom of that second board.
By the way, I read your post about losing everything you had written. I know how frustrating that is. I just want to thank you again for taking the time out to rewrite it.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

I am such an idiot. I put the second board back in without taking pics of the bottom. I will remove it again and get those pics uploaded. Sorry for my oversight. I am getting worn out.

[CapLeaker]

Re: Power-One solar Inverter driving me NUTS!!!

Can we have a picture of the second board the bottom? Haven't seen that yet. Thx.

BTW, I wanna figure out what the deal is between the GRP plug and the GND, there shouldn't be continuity there. Something is a miss somewhere that involves the GRP plug, the HVDC positive and negative and earth gnd.

Some numbered GP screw holes don't look good in the pictures.

[CapLeaker]

Re: Power-One solar Inverter driving me NUTS!!!

I think in the chassis they are all connected. Out of the chassis they are not. Its just a GRound Point to me.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

Dies anyone know what GRP means? Is it something like Ground Return Path or Pole? Just wondering if this is the case then it may be some kind of loop connection which might render my narrowing the issue it to the second board invalid.

[CapLeaker]

Re: Power-One solar Inverter driving me NUTS!!!

Aaargh shiiiiiiiiiiiiiieeet! Sorry, I lost my long post. So I got to write again and this one is shorter.

The test you did on the first board negative to earth GND ringing it at 24MOhm is good, that is what I would expect.
The test with positive to earth GND at 3.2 looks kind of suspicious, but at the same time it could be normal for this thing.
The 1MOhm tests on the other board, I am not buying that this is any good.

As more voltage you got, the more MOhm or isolation you need! My solar inverter has three strings at 800V, 800V and 700V DC. IF my isolation in the inverter would be only 1MOhm, my house would be burnt to the ground. Period.

I also think that the numbered GRP screw holes are GRound Points. However I don't think they are connected together if the board is out and you measure from one numbered GRP hole to another one on the opposite side of the board. What I am getting at is that the ground is only fully working, if all screws are used to mount the board to the chassis AND providing that they make proper connection between the PCB and the chassis too! Otherwise you end up with one GRP pin floating which makes the unit not work either.

I am suggesting following tests board installed and out of the chassis:
-> With the first board out of the chassis check the numbered GRP screw holes against a different one throughout the board. Probably most are open.
-> Measure the same thing installed in the board and you should have continuity on all GRP points.
->With the first board installed (but no wires connected) check the continuity between earth ground and the GRP plug on the back where the wire plugs in.
then go earth or GRP plug one by one over to the Boost1, Boost2, Bulk etc.

Once you figured out the grounding or GRP point situation, install the second board (with the big caps)into the chassis and don't hook any of the wires up.
-> earth ground to GRP plug on the second board. If they are connected, do:
-> earth or GRP plug to Boost1, then over to Boost 2, Bulk etc. one by one.

I know this is painful, but lets see what this does. Over all I say the problem is on the second board with the big capacitors ringing it at 1MOhm. That can't be right.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

This other board is at least a 4 layer PCB. Very hard to trace things. I don't know how to accurately test the blue caps in the attached photo. I did put the megger to them and they came back over 4000 megaOhms. I also checked as many of the SMD components as I could, and I could not find any short. The seven LGBT looking devices have absolutely no markings that I can see on them. I did test them for shorts and could not find a short, but that's the extent of the testing that I was able to do. Those heat sink clamps are very difficult to get off and I haven't attempted to do that yet. Maybe there's a marking underneath them but I'm not sure. Anyhow, I have taken some better close-up photos of that board and attach them.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

I went over these pictures again and maybe I found something or not. LOL
If you look at that spot I marked, it looks like a dark area (like a light burn mark) compared to the others.

Take your DMM in diode mode and check the 3 legs of all the IGBTs and diodes on this board. See if they are shorted or leaky.
How to IGBT? Here: https://www.incbtech.com/circuit-ben...s-ins045e.html

I did check those large IGBTs for shorts and I found none. As for “leaky”, I don't know how to check for that. Also could not find any shorts on the few SMDs that I checked but I was not thorough. Will do it again. What about those 3 blue caps? How can I check them for leakage? Will the megger do it?

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

Test results with second board completely disconnected. Testing form Pos/Neg DC input terminals to ground. Both sets of inputs seemed to yield same results so I will just list the results

Positive terminal
Initial reading at test start - 1.6 megaohms
ONE MIN - 2.4 megaohms
THREE MIN - 3.1 megaohms
FIVE MIN - 3.2 megaohms (seemed to top out at this reading)

Negative terminal
Initial reading at test start - 1.6 megaohms
ONE MIN - 2.8 megaohms
THREE MIN - 8.7 megaohms
FIVE MIN - 24 megaohms (continues to climb but I stopped at 5 min)




TEST with other board connected.

1.0 to 1.1 megaOhms on both positive and negative. Test for one minute

When unplugging GRP, Boost 1, Boost 2, and BULK the readings jump up to 10 megaohms or so. So either this board or the transformers seem to be the culprit.

[CapLeaker]

Re: Power-One solar Inverter driving me NUTS!!!

That’s what I thought is going to happen. First board you get the rising MOhms and with the second board you get the shitty 1Meg reading. Keep going!

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

I’m actually driving right now but I don’t wanna keep anyone in suspense so I will give you just some preliminary findings for now. When I tested the large board with the mega after about one minute I got about 2.4 mega ohms both on the positive and the negative. However, those numbers continued to climb and after about five minutes they were in the 40 megaohm range. When I connected the other board, with the floor, large capacitors the readings seemed to stay locked at a little over one megaohm. I still have to do some more testing when I get home but what do you think of these results so far?

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

If there is any path, the megger will show it.

I got the megger and I am getting some interesting results. However, I just got called out on a job. I’m gonna try to finish it up really quick and come back and continue the testing then I will report back the full results. Thank you guys so much.

[truclacicr]

Re: Power-One solar Inverter driving me NUTS!!!

I see the two CASR/25/SP3 devices that are current transducers on the boosts. Could these be the detection devices?

AFAICT, those devices only sense the current in the BOOST leg. There is nothing on that PCB which senses the current in the GRP leg.

[CapLeaker]

Re: Power-One solar Inverter driving me NUTS!!!

If there is any path, the megger will show it.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

The block diagram on page 4 of that other inverter is showing that there is a device which is sensing the total current flowing through that loop. Let's call it a current transformer.

Let's say panel #1 is producing 100A and panel #2 is producing 120A. This means that the total current flowing through the loop is 100A - 100A + 120A - 120A = 0. This produces zero flux in the transformer, so the output of the secondary winding is 0.

Now let's imagine that current is leaking to building ground from one of the panels. The current through the loop might now be 100A - 99.9A + 120A - 120A = 100mA. There is now some magnetic flux in the transformer, which induces a current in the secondary, which triggers the GFCI.

In your case the respective conductors are BOOST1, BOOST2 and GRP (combined negative outputs from both panels). You need to find some component through which all these currents pass. At least that's how I see it, otherwise I'm stumped, too.

ok makes sense. My brain is still trying to comprehend this information but I am sure within a few hours of processing it will make sense to me and then I will have a new "set of eyeglasses" so to speak, which will allow me to take a clearer and more educated look.

On a second thought, does this mean the megger might not help me since the leakage could be as small as 100mA?

I see the two CASR/25/SP3 devices that are current transducers on the boosts. Could these be the detection devices? If so, what if I swap them with the two on the AC side to see if it makes a difference or would that be a moot point?

[truclacicr]

Re: Power-One solar Inverter driving me NUTS!!!

The block diagram on page 4 of that other inverter is showing that there is a device which is sensing the total current flowing through that loop. Let's call it a current transformer.

Let's say panel #1 is producing 100A and panel #2 is producing 120A. This means that the total current flowing through the loop is 100A - 100A + 120A - 120A = 0. This produces zero flux in the transformer, so the output of the secondary winding is 0.

Now let's imagine that current is leaking to building ground from one of the panels. The current through the loop might now be 100A - 99.9A + 120A - 120A = 100mA. There is now some magnetic flux in the transformer, which induces a current in the secondary, which triggers the GFCI.

In your case the respective conductors are BOOST1, BOOST2 and GRP (combined negative outputs from both panels). You need to find some component through which all these currents pass. At least that's how I see it, otherwise I'm stumped, too.

Note that my discussion is relevant for AC current transformers, but DC current transformers work a little differently. They typically use Hall effect sensors rather than a secondary winding.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

Look at page 4 of this document:

https://cdn.badcaps-static.com/pdfs/...95a1307f0b.pdf

Notice that the positive and negative PV conductors pass through a detection device that senses the net current and produces a GFCI interrupt to the controller if the sensed net current is non-zero. That's the way that an RCD / ELCB works.

This link will not open for me for some reason.

edit: scratch that, it just opened.

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

That Meder device appears to be a 12V reed relay.

https://cdn.badcaps-static.com/pdfs/...147bd57807.pdf

Yes you are correct. I did remove this relay and check it. It is good. I also soldered some wires to the pins/legs
and extended them out of the unit so I can check if this relay is getting the 12 V power when the inverter is powered on. It is not, and I suspect that it should if I’m not mistaken.

I simply checked it by applying 12 V DC to it and checking if the contacts closed and they did. I also checked all the small components adjacent to it and they all seem to test good. I even removed all of the SMD mosfets and transistors and tested them outside of the board with my transistor tester and they all tested good. Just for the heck of it, I had ordered new ones anyway and I put the new ones in but it didn’t seem to solve anything so I put the old ones right back

[mitsu2k]

Re: Power-One solar Inverter driving me NUTS!!!

Look at page 4 of this document:

https://cdn.badcaps-static.com/pdfs/...95a1307f0b.pdf

Notice that the positive and negative PV conductors pass through a detection device that senses the net current and produces a GFCI interrupt to the controller if the sensed net current is non-zero. That's the way that an RCD / ELCB works.

Can you please elaborate on this? I am not as professional and experienced as you. If you could do a markup in the photo that would be great.

I think you are talking about the current sensors on the left hand side back of the board on the PV side of the board.