Power-One solar Inverter driving me NUTS!!!

[mitsu2k]

Yes you are probably correct. I will try and test all components in that area to the best of my ability. So far I did not see anything that was shorted. That silicone type coating all over the board makes it difficult.

[petehall347]

the lamp circuit will be fine i guess . what i am trying to see is what turns it on and then see what tells it to come on . there must be something that measures the resistance to earth ground from panel outputs and i suspect something there is amiss . datasheet for the mcu might help a bit .

[mitsu2k]

Not sure which one is the MCU for this circuit. I do know the alarm relay is on this corner of the board. Do you think this might be the MCU? Sorry for the upside down pic. it’s the only way I can get it under my microscope.

edit: looks like that one is a USB to serial

[CapLeaker]

You are on the wrong board.

[petehall347]

TUSB34101 USB
to Serial Port Controller

[mitsu2k]

The strange part is that the GFI LED comes on instantly before the unit has time to go through its checks. I have seen videos online where the LED did not come on until after the checks.

[petehall347]

from what i can make out its behaving correctly its only the "A" models that dont halt at this fault . unless yours is an "A" model

[mitsu2k]

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

[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

[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]

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.

[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.

[petehall347]

this post does not exist . honest .

[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?

[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.

[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 .

[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.

[CapLeaker]

The third leg is a thermal fuse.

[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]

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]

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?