PIP inverter repairs and hardware modifications

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calida82
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

Hi, I don't think I have a problem on RCBO, mine is already 300mA changed less than a year ago, I had a 30mA one before and every rain it clicked. I called an electrician and he told me that the photovoltaic needed 300mA so he replaced it and it worked so far without tripping on rainy days,
I tried to mount the 30mA one again for test which gave problems only when it rained. yesterday it was sunny and that too. Now the inverter is disconnected from all its loads the only thing that powers rcbo is the inverter so the problem must be there.

I tried to remove the yellow mov card and the par card I read was giving problems of this type, but the rcbo still jumps. I tried to measure the voltage on the green movs. Mov 2 is always powered when rcbo is on and there is no voltage on its ground pin, mov 3 is powered only when I put the inverter on and you hear the relays trip, on one pin I can measure 40v when the rcbo is triggered, on the other 0v. I also tried to tap on the 3 black relays in case there were some pins glued but nothing has changed.
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Re: PIP inverter repairs and hardware modifications

Post by coulomb »

calida82 wrote: Sat, 21 Aug 2021, 17:34mov 3 is powered only when I put the inverter on and you hear the relays trip, on one pin I can measure 40v when the rcbo is triggered, on the other 0v.
I think that's a big clue. From your photo, it looks like MOV3 connects between AC-ln neutral and earth. AC-in neutral should always be a earth potential, at least in Australia, due to the neutral to earth bond at the switchboard. If there is suddenly 40 V between AC-in neutral and earth, that means that neutral current is flowing in some bad paths, no doubt leading to the triggering of the RCBO.

I think you need to trace out your neutral wiring carefully. Remember that one of your relays probably has a double throw (not not certainly, depending on age), it would be RY1 on the one I have here (connecting AC-in N to AC-out N and all the other neutrals. When it's not connecting N-out to N-in, it should be connecting N-out to earth. You can check this with a multimeter when everything is powered down. I can't immediately think of a circuit that would put 40 VAC at AC-in N only in bypass mode, but you must have it somehow.

Is your utility neutral supposed to be connected to earth at the utility transformer? I suppose if that connection has failed, that could explain the 40 V. But it could be a loose neutral connection (at AC-in) if your utility neutral is well earthed. If you have an unexpectedly high neutral potential, it's dangerous and your utility company should be quick to rectify it.
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

i checked, the mov where i detect 40v is connected to the AC input terminal.
I checked with a multimeter the volts between neutral and earth and it is 0v I checked the continuity between neutral and earth and it gives me about 450ohm.
is there a diagram where i can follow the neutral inside the inverter? what happens is this the measurement I made between earth and neutral right on the inverter ac input terminals

https://www.youtube.com/watch?v=htsR7JCpYLU

does the relay ry1 connect and disconnect only the neutral does not come into contact with the phase in any way?
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Re: PIP inverter repairs and hardware modifications

Post by coulomb »

calida82 wrote: Sat, 21 Aug 2021, 19:30 is there a diagram where i can follow the neutral inside the inverter?
There is no complete, modern schematic available to the public, as far as I know.

I have annotated the very broad block diagram below to show the essentials. The RYn designators are for the 2013 model that I have here for tracing; they may well have changed designators by now. For example, this one has MOV3 across L and N of AC-in; it sounds like yours is between AC-in N and earth.

AC-out to E relay contact 2.png
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

in this chema, however, I do not see any point where the phase can meet the neutral ...
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Re: PIP inverter repairs and hardware modifications

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calida82 wrote: Sat, 21 Aug 2021, 22:19 in this chema, however, I do not see any point where the phase can meet the neutral ...
I don't think that your RCBO is tripping due to short circuit, i.e. over-current, I think it's tripping due to unbalanced neutral and active current through the RCBO. This won't be due to too much capacitance to earth, as I originally thought (300 mA is quite a lot of capacitive current), but due to some of the load current flowing through earth conductors. So this seems like an installation problem now.

Thinking more about it, it's probably a poor connection to earth from the earth terminals to real earth. Or a poor connection from the case of the inverter to where the relay earths the AC-out neutral (assuming that it has the two throws). This could be due to a missing screw. Since the inverter has been in for repair by people that may not be fully technically savvy, this seems likely. It could also be a burned contact in that relay. Incompetent connection of the test rig might cause that.

[ Edit: Any screw hole with the earth symbol in a circle near it must have a screw in it. If you run out of screws when reassembling, don't leave out a screw from those holes, leave it out of some other hole, or preferably have a supply of spare screws. Hopefully the repair centre would have spare screws, but it's easy to overlook one or two screws out of about 19, especially when their locations are somewhat random. This warning is not necessarily for you, @Calida82, but for other readers who might try their hand at electronic repair. ]

By the way, since 300 mA is way past lethal current, you should install another 30 mA RCBO at the output of the inverter, if you have not already done so.
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Re: PIP inverter repairs and hardware modifications

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coulomb wrote: Sun, 22 Aug 2021, 06:34 Or a poor connection from the case of the inverter to where the relay earths the AC-out neutral (assuming that it has the two throws).
I've just taken another look at one of your photos, and the relay next to MOV3 is indeed double throw; you can tell by the "schematic" written on top.

Edit: See the "schematic" in red below, compared to the ordinary single throw relay in green. Note also the earth in a circle symbol in blue. I can't tell if the screw is missing in that photo.

Double throw relay.jpg
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Re: PIP inverter repairs and hardware modifications

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calida82 wrote: Sat, 21 Aug 2021, 19:30
I checked with a multimeter the volts between neutral and earth and it is 0v I checked the continuity between neutral and earth and it gives me about 450ohm.
If this is at the input to the inverter it should not be 450ohm it should be less than 10ohm.
If its at the output, you have found the problem.
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

[ Edited Coulomb: Arrgh! So sorry. I've edited instead of replied to your post. As an administrator, the forum software lets me do that. Sigh.

So ¾ of your post is gone, sorry. ]

Ground connection is ok. I had to redo it 2 years ago ...

The inverter has been working ungrounded for a couple of months, this as said happened 2 years ago, could it have caused this damage?
...

Now if I measure between phase and earth I measure 227v if I try the continuity between neutral and earth I get 300/400 ohm (re-measured this morning).

...
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Re: PIP inverter repairs and hardware modifications

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removed the card.
at first glance, no component seems to have exploded. the RY1 relay is currently at rest and its rest corresponds to the earth, tested on a life pin where the earth symbol is present. on the relay it says coil 12VDC even if on the datasheet it says coil 5-100v. I would like to try to power the relay with external 12v to see if there is an exchange but I don't know which is the + pole and the - pole on the board, I don't want to put + on - and fry everything. for the moment I would like to avoid removing it because the warranty ended in June, but the two times that I sent it for assistance and it remained there every time a month they always told me that everything was ok, after the last repair I warned that the inverter always did the defect 08. now I don't know if things can be connected, but now that the problem is evident they cannot say that everything is ok ....
as soon as they reopen from the holidays I want to call them and hear what they have to say. if, on the other hand, I have the certainty of solving the guarantee by myself to hell with it and I will repair it myself
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Re: PIP inverter repairs and hardware modifications

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coulomb wrote: Sun, 22 Aug 2021, 06:34 Ground connection is ok. I had to redo it 2 years ago ...
OK, that connects the earth conductors to earth, but in Australia and most parts of the world, neutral is bonded to the earth conductor at the switchboard. So you should not be seeing 300-400 Ω between the neutral and earth at the AC-in terminals of the inverter. You did not say what part of the world you are in, or what earthing convention is used in your area, so I don't know whether you need to get that fixed or not. If you use a TT system, I don't know how that will react with the inverter earthing the utility neutral briefly. That might be the source of your problem.
The inverter has been working ungrounded for a couple of months, this as said happened 2 years ago, could it have caused this damage?
I'm still not convinced that the inverter is damaged, and I can't see how a floating neutral could have damaged the inverter. Neutral to earth bonding is to protect people, not equipment.
Now if I measure between phase and earth I measure 227v if I try the continuity between neutral and earth I get 300/400 ohm (re-measured this morning).
Is this 300-400 Ω between utility neutral and switchboard earth, or AC-in neutral and earth on the inverter, which I think you said has some 2 VAC between them? I assume that this 2 VAC varies with time, depending on other loads on the utility's transformer.
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

coulomb wrote: Sun, 22 Aug 2021, 18:18
coulomb wrote: Sun, 22 Aug 2021, 06:34 Ground connection is ok. I had to redo it 2 years ago ...
OK, that connects the earth conductors to earth, but in Australia and most parts of the world, neutral is bonded to the earth conductor at the switchboard. So you should not be seeing 300-400 Ω between the neutral and earth at the AC-in terminals of the inverter. You did not say what part of the world you are in, or what earthing convention is used in your area, so I don't know whether you need to get that fixed or not. If you use a TT system, I don't know how that will react with the inverter earthing the utility neutral briefly. That might be the source of your problem.
The inverter has been working ungrounded for a couple of months, this as said happened 2 years ago, could it have caused this damage?
I'm still not convinced that the inverter is damaged, and I can't see how a floating neutral could have damaged the inverter. Neutral to earth bonding is to protect people, not equipment.
Now if I measure between phase and earth I measure 227v if I try the continuity between neutral and earth I get 300/400 ohm (re-measured this morning).
Is this 300-400 Ω between utility neutral and switchboard earth, or AC-in neutral and earth on the inverter, which I think you said has some 2 VAC between them? I assume that this 2 VAC varies with time, depending on other loads on the utility's transformer.
I am in Italy and my system should be TT. I checked there is a law indicating the maximum resistance between earth and neutral at 180 ohms. I am not an expert in AC systems so I made the mistake of measuring the resistance between earth and neutral with the loads in operation ... I was wrong. The doubt arose now that I went again to measure and I got over 800ohm then after a few minutes again 300ohm. now I have to wait until it gets dark to be able to disconnect the main RCBO and perform the measurement upstream of it. Unfortunately, I believe instead that the fault lies in the inveter. I have not added new appliances, the night it stopped working there were no rains or thunderstorms, only a slight humidity of what you find in the morning on the windows of the cars. without inverter the rcbo never tripped. anything can happen but it seems very strange to me. what I impotise happened is that on the day of the fault there were several clouds that did not leave rain, the same night the lack of humidity triggered the error 08 like other times it happened and on the first restart caused by the error 08 something went wrong and something went wrong ....

the neutral and ac-in phase of the inveter are the same as those coming out of the main RCBO. as far as the ground of the inverter both outgoing and incoming is concerned, I only brought a ground cable from my panel to the inverter and then I made a bridge between ground in and ground out, I believe that this does not create problems or earth in and earth out must be in two separate earth poles?
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Re: PIP inverter repairs and hardware modifications

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there is something wrong I don't understand.
I got off where the main rcbo is and I deactivated it, only one electronic counter (sdm120) remained active, I don't know why it is upstream of the rcbo, I take the measurement and read about 500ohm ... I wait a couple of minutes and 500ohm again ... I try to turn the multimeter test leads what was in the ground I put it in the neutral and what was in the neutral in the ground, and in this way I read -300ohm ... I reconnect as before and 500ohm again .. why does this happen?
measured in ohms the muzzle should remain the same regardless of the direction of the tips
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Re: PIP inverter repairs and hardware modifications

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calida82 wrote: Mon, 23 Aug 2021, 05:02why does this happen?
measured in ohms the muzzle should remain the same regardless of the direction of the tips
It's because of the neutral to earth voltage, I believe. We have a type of TN-C-S system called Multiple Earthed Neutral in Australia. But you have TT, meaning that the earth for your outlets and other devices comes from the local earth rod. If you have 100 customers on the utility transformer, the load current in the neutral wire multiplied by its resistance comes to typically a few volts. If the earth has no potential across it (I have no idea how true that is, but it seems reasonable for the few hundred metres to the local transformer), then this voltage drop will appear between incoming neutral and local earth.

Your multimeter measures resistance by injecting a known current and measuring the resultant voltage rise. But if there is voltage there (from hundreds of amps through the neutral conductor), the test voltage rise is swamped by the existing voltage, and the measurement is invalid. As to why it depends on the direction when the AC should be symmetrical, I don't know; it could be some sort of non-linearity that occurs when your multimeter gets voltages higher than expected. It's expecting to see DC, yet it finds AC; who knows how it reacts.

So around two volts neutral to local earth is quite acceptable. You did mention 40 V neutral to earth at one point; that is certainly not acceptable. I think we need to concentrate on that problem.

BTW, I didn't realise this (not thinking TT systems), but your RCD is probably your main breaker for the whole apartment. TT systems rely on the RCD for phase to earth faults, since the local earth is typically not low impedance enough to cause an ordinary breaker to trip. So in a TT system, you absolutely will always have an RCD upstream from the inverter. I'm surprised that this doesn't cause more problems with nuisance tripping. But with your 300 mA main RCD, you should not be having problems, assuming that the RCD isn't excessively sensitive (i.e. tripping at less than the advertised 300 mA of current differential).
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Re: PIP inverter repairs and hardware modifications

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calida82 wrote: Mon, 23 Aug 2021, 04:15as far as the ground of the inverter both outgoing and incoming is concerned, I only brought a ground cable from my panel to the inverter and then I made a bridge between ground in and ground out, I believe that this does not create problems or earth in and earth out must be in two separate earth poles?
That should be fine; there is no need for separate earth rods or the like.
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Re: PIP inverter repairs and hardware modifications

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the power company's grid transformer is 50 meters from my house.
I had read that 2v on the neutral can normally be found during measurements.
My 0.3A circuit breaker has little life time and in its life before this fault it will have tripped yes and no 3/4 times.
the inverter worked for a long time with a 0.03A differential, tripping only when there was a lot of humidity. however, I tried to connect the inverter to two other differentials always from 0.03A. I have no other bigger ones and they both jumped.
yes when the differential trips on the neutral ac-in I read 40V, this turns on when the inverter tries to switch to bypass mode and you can hear the relays trip inside the inverter. If the inverter does not go into bypass it normally produces energy by itself.
i tried to figure out something from the ry1 relay. the ac-in cable N arrives at a pin of the RY1 relay which at rest this pin remains in normally open (NO),
however, the other NC pin does not go to earth. I would like to be able to test the relay but without removing it from the card.
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Re: PIP inverter repairs and hardware modifications

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calida82 wrote: Mon, 23 Aug 2021, 13:36I would like to be able to test the relay but without removing it from the card.
It should be possible to apply 12 V from a current limited power supply (100 mA should be enough) with the polarity indicated:

RLY1,3 drivers.png
RLY1,3 drivers.png (28.74 KiB) Viewed 2649 times
Note that relays RY1 and RY3, the "safety" relays, come on together (AC-in neutral and active respectively).
The circuit around Q34 is to briefly send almost 24 V to the relays, to pull them in as fast as possible.

To find the right end of the coil to apply the 12 V, find two relay coils that are connected to each other, and probably to the positive side of C48:

MKS II C48.jpg
MKS II C48.jpg (121.23 KiB) Viewed 2649 times
Underneath my old 2013 main board, showing the location of RY1 and its coil pins:

RLY1 on 2013 model sm.jpg
RLY1 on 2013 model sm.jpg (281.23 KiB) Viewed 2649 times
The layout under your Axpert MKS II will be very different, but many of the designators will likely be the same, so I hope it helps. Note that on this old model, RY1 is single throw, so it doesn't have the third terminal to connect to earth. It will be interesting to learn why your model doesn't seem to connect the normally closed contact to earth. My understanding is that all models since PaulVK pointed out the problem to Voltronic, in 2017 or so, have this extra throw to ground the inverter output when the safety relays are off (no connection to utility neutral).
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Re: PIP inverter repairs and hardware modifications

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The last photo, the ones where you marked RY1 in yellow on my card, seems to be RY3 in fact immediately on the right there are the contacts for the RY2 relay slightly higher.
I talked to some technicians about the electrical supply, I work as a mechanic and they are my customers, they told me that actually 400ohm between earth and neutral is a lot, they advised me to try putting a new earth braid. they also told me that this measurement must be carried out with a special instrument, the classic multimeter is not suitable for this measurement. so my measurement could also be biased. They told me to try a fresh ground installation, but according to them the problem lies in the faulty inverter.
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Re: PIP inverter repairs and hardware modifications

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I made some measurements, if I can use the mass of the capacitor C48 as a reference ground for this circuit, the pin closest to the RY3 relay corresponds to the ground and not to the positive as in your case
PXL_20210823_215013327.jpg
PXL_20210823_215013327.jpg (384.69 KiB) Viewed 2615 times
I also checked the RY1 and one of its pins where the contact remains when everything is still (if the contact is not glued which is what I want to find out) goes to the earth. the hole next to the relay on the opposite face of the board has a pad with the earth symbol. when I said it wasn't, I had measured the earth elsewhere on the board. I noticed however that the mark left by the screw in that hole just turns the pitch off. I am sure that bolt has never been removed before I did it, the card remained in its case until I removed it, I removed the seal above the screw that holds the card where the cables are connected battery.
is that little contact that the screw has enough?
if the relay is stuck in this position can it make me trip the differential?
PXL_20210823_221824806.jpg
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Re: PIP inverter repairs and hardware modifications

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calida82 wrote: Tue, 24 Aug 2021, 06:36 I made some measurements, if I can use the mass of the capacitor C48 as a reference ground for this circuit, the pin closest to the RY3 relay corresponds to the ground and not to the positive as in your case
Yes, so you should me making measurements from the other side of the capacitor, the positive end.
I also checked the RY1 and one of its pins where the contact remains when everything is still (if the contact is not glued which is what I want to find out) goes to the earth. the hole next to the relay on the opposite face of the board has a pad with the earth symbol. when I said it wasn't, I had measured the earth elsewhere on the board. I noticed however that the mark left by the screw in that hole just turns the pitch off.

I think we're having translation problems with the last part. The lighting in your photos is unusual, but it looks like there is solder mask/resist over the pads that the screw goes through. That should not be the case; you obviously need shiny tinned copper to make contact with the screw (on top of the board) and the metal spacer (under the board). You may need to carefully scrape away that solder mask (the green covering that stops solder from shorting nearby pads to each other) around the hole.

[ Edit: on further examination on my computer rather than my phone, it looks like they keep the copper well away from the hole. I have no idea why they do that. If the screw's flange isn't large enough to reliably connect to the track on top (it looks like it doesn't have an earth track at all underneath the board), then you might need a suitably sized star washer to make good contact. The sharp corners of the star washer should also help penetrate any dirt/oxide on the top track. ]

However, I don't see how poor contact would cause your problem (it could of course cause other, safety related problems).
is that little contact that the screw has enough?
It would be if the solder mask isn't interfering with contact. [ Edit: and the screw's flange is large enough to make contact, and/or has a suitable washer. ]
if the relay is stuck in this position can it make me trip the differential?
Yes, I think it would. Presuming that the other relays are working, AC-in active would connect to the loads, but AC-in neutral would not. Any power to the loads would have to return by other paths (e.g. through earth conductors), and that would unbalance the current going through the RCD, so it would trip if the load was at least 300 mA (around 66 VA).

Edit: Sigh. I'm not thinking TT here. Your system won't have a great contact between earth and neutral; neutral load current will attempt to flow via your earth stake (presuming that you have a reasonable connection to earth via that PCB screw). So likely the loads won't get much power in this situation, but with large loads (well over 66 VA), enough current would go through your earth stake to trip the RCD.

I was thinking that the 30 mA RCD protecting your loads would have tripped first, but if that relay is stuck inside the inverter, all the load neutral current will flow through that RCD back to the relay and then through the earth stake. So the 30 mA RCD would not trip, and that 300 mA RCD would be the only thing protecting you from a high neutral voltage at your devices, and load current flowing through protective earth conductors. Not a massive safety risk, but still.
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Re: PIP inverter repairs and hardware modifications

Post by paulvk »

The TT system Note the last bit

Main characteristics
Simplest solution to design and install. Used in installations supplied directly by the public LV distribution network.
Does not require continuous monitoring during operation (a periodic check on the RCDs may be necessary).
Protection is ensured by special devices, the residual current devices (RCD), which also prevent the risk of fire when they are set to ≤ 500 mA.
Each insulation fault results in an interruption in the supply of power, however the outage is limited to the faulty circuit by installing the RCDs in series (selective RCDs) or in parallel (circuit selection).
Loads or parts of the installation which, during normal operation, cause high leakage currents, require special measures to avoid nuisance tripping, i.e. supply the loads with a separation transformer or use specific RCDs

Image
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

coulomb wrote: Tue, 24 Aug 2021, 07:47
Yes, so you should me making measurements from the other side of the capacitor, the positive end.
I measured between the positive of the capacitor c48 and the pins of the relay coils and by measuring in this way the positive seems to coincide with that of your diagram, with a resistance of 0 ohm where you have marked positive and 150ohm the other. but why if I measure on the legative side I get the opposite?
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Re: PIP inverter repairs and hardware modifications

Post by coulomb »

calida82 wrote: Tue, 24 Aug 2021, 19:45 I measured between the positive of the capacitor c48 and the pins of the relay coils and by measuring in this way the positive seems to coincide with that of your diagram, with a resistance of 0 ohm where you have marked positive and 150ohm the other. but why if I measure on the legative side I get the opposite?
Ignore the negative end of the capacitor. We just need to find two coils that connect 0Ω to each other and to the positive end. These coil ends will be the positive ends, so you know which way to safely apply 12 V from a current limited power supply. That should tell you whether the relay is operating or stuck, either from the sound, or better yet by measuring conductivity between the AC-out neutral terminal and earth (on the PCB at the earth screw hole, because the PCB won't be bolted to the chassis).

I mention the capacitor because I thought it would make things easier, and to eliminate the possibility of two coils connected to earth; these would then be negative ends.
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calida82
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

I tested the RY1 and RY3 relays by powering them with external 12v, unfortunately the 2 relays work ... measured continuity on the pins on both.
trying to find something I found that on capacitor C122 I find continuity at its ends which are respectively the neutral output from the inverter and the earth. Could this be normal or could this be the problem?
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calida82
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Re: PIP inverter repairs and hardware modifications

Post by calida82 »

I answer myself, yes it is normal, it is the RY1 that at rest brings the neutral to earth ....
Do you think it is the case that I begin to unsolder the mov i have to look elsewhere to find the fault?
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