Power-One solar Inverter driving me NUTS!!!

[mitsu2k]

troubleshooting is page 49 onwards

OK I think I know what you are referring to now. Please see attached. This is the only test that I can see that would be relevant. And I did perform this test in the following manner:

tested between positive and earth ground and got over 50 MegaOhms.

got approximately the same results from negative to earth ground.

I did not short the positive and negative together because it was daytime and I didn't think that would be a good idea being that there's about 256 V there. However, I wouldn't expect to see any different results if I shorted them being that they were both over 50 mega anyway. I suppose I can do this test at night, but I am just afraid of blowing the diodes on the panels and I don't really want to go up on the roof being that I am afraid of heights

[petehall347]

troubleshooting is page 49 onwards

[mitsu2k]

I hope you mean MOhm not mOhm. There is a huge difference between Mega and Milli

Yes I meant MegaOhms

[mitsu2k]

Did you do the test procedure that is outlined in this maintenance manual
Did you follow it exactly or did you deviate from what they have and if you did please explain how you did it differently
Also if you did run the test as they outlined in the manual what were your results for each section of tests
https://www.badcaps.net/filedata/fetch?id=3153508

I have not seen any test in any maintenance manual. Where are you seeing this?

[CapLeaker]

I tested between the first and third legs in my photo. Here are the results.

500vdc test

#1
175 mOhms

#2
205 mOhms

#3
215 mOhms

#4
239 mOhms

I also tested the two blue ones on the AC side and those tested over 4000 mOhms. (full scale on megger)

Not sure what these results mean. Could all 4 of them be bad?

I hope you mean MOhm not mOhm. There is a huge difference between Mega and Milli

See, MOVs degrade with time and how often the get zapped. The insulation layer will break down each time it gets hit, to a point of leaking or total failure (basically a short). A 175 Mega Ohms is not a failure, but it's getting time to change it out. All depends on what the rating of this MOV is and how much voltage you use with the Megger,
Let's say you hit a 375V MOV with 500V from the Megger, it will hurt the MOV each time you press the test button.

[sam_sam_sam]

I tested between the first and third legs in my photo. Here are the results.

500vdc test

#1
175 mOhms

#2
205 mOhms

#3
215 mOhms

#4
239 mOhms

Did you do the test procedure that is outlined in this maintenance manual
Did you follow it exactly or did you deviate from what they have and if you did please explain how you did it differently
Also if you did run the test as they outlined in the manual what were your results for each section of tests
https://www.badcaps.net/filedata/fetch?id=3153508

[mitsu2k]

I tested between the first and third legs in my photo. Here are the results.

500vdc test

#1
175 mOhms

#2
205 mOhms

#3
215 mOhms

#4
239 mOhms

I also tested the two blue ones on the AC side and those tested over 4000 mOhms. (full scale on megger)

Not sure what these results mean. Could all 4 of them be bad?

[CapLeaker]

2 is the middle leg. Number 3 is the closest leg to 2. Number 1 is the furthest away from leg 2 (middle pin).

leg 2 to leg 3 is the thermal fuse and should read a dead short.
leg 1 to leg 3 is the MOV and it should be either OL or full scale resistance on the Megger.

[mitsu2k]

The third leg is a thermal fuse.

so which legs do I test across with the megger?

Legs 1 and 2 from left to right test short.

[CapLeaker]

The third leg is a thermal fuse.

[mitsu2k]

best way to test MOVs is with the Megger, Put 250V or whatever their max rating is on there and if the Megger ranges out, they are good to go.

These are 3 legged MOVs. The middle leg on the positive terminals seems to be connected directly to earth ground.

[petehall347]

Not sure what the “A” model is but here is the labels

i would expect the A to be part of the model number . maybe the manual has clues about it .

[CapLeaker]

I have a question about the MOVs. None of them look discolored or show any signs of heat. They test open with DMM. I know this is not a proper test but should I just not worry about these?

best way to test MOVs is with the Megger, Put 250V or whatever their max rating is on there and if the Megger ranges out, they are good to go.

[mitsu2k]

I have a question about the MOVs. None of them look discolored or show any signs of heat. They test open with DMM. I know this is not a proper test but should I just not worry about these?

[petehall347]

this post does not exist . honest .

[CapLeaker]

OK now I’m thinking there is really a ground fault. When I connected it back up to the array and turned it on, I tried to measure current from positive, DC, negative DC, to earth ground. I was not able to measure any current, but when on the positive and touching the earth ground with my probe, I noticed very slight arching. I don’t get this arcing on the negative side.

I don’t think that should be the case. When I measured for voltage between the positive terminal and earth ground, I get approximately 149 V. Between the negative and earth ground I get approximately 87 V. The array itself positive to negative measures approximately 256 V. When I disconnect the array from the inverter and just measure the positive and negative coming from the array to earth ground I get very low transient voltage, like 5 to 10 V.

but the question is, where could this leakage be?

edit: when I remove the 4 red MOVs and perform the above test again, I get practically no voltage from negative to earth ground but the voltage from positive to earth ground jumps up to about 191v

That sounds like a real ground fault all right. I would start again bare ass from square one. This time take as sheet of paper and make nots want you did, how you did it and what the result was.
i do have a document that comes with a different inverter that deals with this on the solar side.

[mitsu2k]

leakage is on the negative if indeed there is any leakage .. the measurements suggest there is . maybe a cable is damaged or got water inside it .

Are you referring to the cables coming from the array? I tested those disconnected from the inverter and they seem to test fine. I tested them with a mega and the resistance was in the high mega ohms on both the positive and the negative to earth ground. The inverter itself measures them above 20 mega Ohms when it performs it start up test.

[petehall347]

leakage is on the negative if indeed there is any leakage .. the measurements suggest there is . maybe a cable is damaged or got water inside it .

[mitsu2k]

OK now I’m thinking there is really a ground fault. When I connected it back up to the array and turned it on, I tried to measure current from positive, DC, negative DC, to earth ground. I was not able to measure any current, but when on the positive and touching the earth ground with my probe, I noticed very slight arching. I don’t get this arcing on the negative side.

I don’t think that should be the case. When I measured for voltage between the positive terminal and earth ground, I get approximately 149 V. Between the negative and earth ground I get approximately 87 V. The array itself positive to negative measures approximately 256 V. When I disconnect the array from the inverter and just measure the positive and negative coming from the array to earth ground I get very low transient voltage, like 5 to 10 V.

but the question is, where could this leakage be?

edit: when I remove the 4 red MOVs and perform the above test again, I get practically no voltage from negative to earth ground but the voltage from positive to earth ground jumps up to about 191v

[mitsu2k]

Not sure what the “A” model is but here is the labels