19 hours ago, maxo said:

I have to dissasemled complete inverter, due on first view, there on main board I have the problem (diode D62=UF304 - it's souronding was slighntly overheated ) and also SMPS transformer TX6 is burnt (outer insulation is completelly brown).

Respect for anyone that can take a electronic board apart and know how to fix it!! I have taken many boards apart but that is for parts not for repairing and every time I look at all those little paths and think , luckily this thing is gone!

On 2017/07/22 at 6:31 PM, maxo said:

PLEASE HELP, any idea where to get the trafo TX6 (I have written even e-mail to Voltronic Power, but no answe yet). 

The partial schematic in this post may help a little:

http://forums.aeva.asn.au/forums/forum_posts.asp?TID=4332&PID=65232&title=pip4048ms-inverter#65232

Also, TX2 (near TX6) may have similar characteristics, so you may be able to get characteristics from TX2 that you can't get from burned up TX6.

Attempting to wind your own transformer deserves respect! But if you fail, it might be possible to get spare parts from a source like MPP Solar. They seem to be the main Ebay seller for Voltronic Power, and seem to have good access to the developers. 

Finally, if all else fails, @plonkster's clever idea of replacing the whole power supply has merit. You can see that its purpose is to supply square wave power to AC_PS_OUT, which I believe is mentioned in one of the service manuals. I'm not at my computer now, but from memory, that supplies isolated 15 V or so to some parts of the inverter.

[ Edit: actually, it appears in this partial schematic here:

http://forums.aeva.asn.au/forums/forum_posts.asp?TID=4332&PID=59548&title=pip4048ms-inverter#59548

So it seems to need a little more than battery voltage, so that diode D59 will be reverse biased, and the battery won't be used to supply power to the inverter control electronics when mains power is available. So something that supplied 55 V or so would be ideal. Alas, that's a bi unusual. Maybe a 48 V supply with an adjustable output turned all the way up would work. ]

If you supply that, perhaps via a diode, [edit: you can use D62 for this, as long as TX6 is removed] using the same mains input that the circuit in the linked post, that should work. Suppliers like Mouser will have small AC to DC power supply modules at reasonable prices that could be made to fit. Taking out the 4 diodes D17-21 would prevent the existing power supply from drawing needless power. 

Edited May 14, 20197 yr by Coulomb

I note that in later models, TX6 doesn't even exist; [ edit: thanks to my colleague Weber for pointing that out] they presumably use the circuit around TX2 instead. Perhaps it's worth tracing the circuit around TX2 to find out what it does. Please post whatever you find.

[ Edit: No No! TX2 is the bus soft start circuit; it pre-charges the large 470μF capacitors to some 400 V before the DC-DC dual full bridges do their job. So TX2's secondary will be a much higher number of turns. Despite appearances, TX2 and TX6 are rather different. (Though maybe they could still be similar if primary and secondary are swapped. But best not to assume any similarity. ]

Please also feel free to post corrections to my trace of the TX6 circuit, if your notes disagree with mine.

Edited July 23, 20178 yr by Coulomb

Hi Coulomb

Thank's for your replys and directions what to do. 

Let start from your first post answer, the circuit diagram in your post No. 65232 is correct and agree's with mine backengineering.
For your info, gate resitor in your schematic marked with question is R233 = 22 OHM .
Another infos about TX6: 
- winding AC_PS_OUT  is done by two parallel enameled Cu wires fi 0,25 mm in diameter each (bifilar winding) between pins 8 and 11 on TX6 transformer, winding has 62 turns
- primary winding (AC through diodes D17-D21 and 33uF capacitor) is done by enamled Cu wire with diameter 0,21 mm between pins 3 and 2 - 90 turns and then between pins 1 and 2 another 90 turns, so primary winding has in total 180 turns
- start up winding and at the same time VCC supply winding for UC3845 (U15) is done between pins 5 and 6, consist 24 turns of Cu enameled wire with diameter 0,21 mm.
Winding princip: start with start up winding 24 turns, followed by 1/2 half of primary winding =90 turns between 1 and 2, followed by 62 secondary bifilar turns betwwn 8 and 11 pin and finally with 90 primary turns of second half or primary winding between pins 3 and 2. 

That's all main inportants about TX6 transformer , was found when I dissasemble it.

About the second link (59548), my circuit is the same, except the connections to U10 ,  where I have drawn different, but not known in this moment, what is correct, mine or yours - need still to be checked again.

About the output from secondary winding of TX6: I believe it must be something over 58V DC = max charge voltage for battery , but I'm not shure about that, if we compare primary transformer voltage - must be around 310V DC and 180turns and secondary turns (62 turns), this AC_PS_OUT could be even higher, but the current is not known and this secondary out possibly be different.

About the TX2 comparing: it looks similar like TX6, but I suspect it is wound for different voltages, but the idea to check the initial permeability is good idea, but at the same time we do not know if there is the central leg gap also, we do not know the turns etc, so we could not compare it and also the big mistake could be done with comparision of unknown values.

I will try on mpp solar page to find the TX6 like you suggest, will reply about the findings.

 

with all the best

 

maxo

 

16 minutes ago, maxo said:

About the TX2 comparing: it looks similar like TX6, but I suspect it is wound for different voltages, but the idea to check the initial permeability is good idea, but at the same time we do not know if there is the central leg gap also, we do not know the turns etc, so we could not compare it and also the big mistake could be done with comparision of unknown values.

Thanks for the details, @maxo. Indeed, the TX2 circuit is completely different to that of TX6; it seems that TX2 is part of the bus soft start circuit (pre-charge for the large 470μF 500 V bus capacitors C40, C41). I've edited my earlier post to correct the error. I'll publish a partial schematic trace on AEVA soon and put a link here.

Thank's Coulomb

for details about the TX2 function, like I assume it seves with different voltages and is wounded completlly different.

Go forward to find the TX6 possibly, all the rest could be done more easilly.

Meanwhile: thanks for plonkster reply, UC3845 is not the problem to find and change at all, there on main board are 3  pcs UC3845, one in DIL8 and two in SMT case, function all of them is to serve 3 separate SMPS,  but the output voltages of this SMPS are for sure different, also their currents. 

Coulumb: do you have any idea, what is the output voltage on TX6 secondary , for VCC for U15 is probably somwhere between 15 and 30V DC , btw. max supply volatge for UC3845 is like I know 36V DC and turn ON = 8,4V and turn off= 7,6 V DC by IC specification .

wbr

maxo

 

54 minutes ago, maxo said:

Coulumb: do you have any idea, what is the output voltage on TX6 secondary ,... 

Alas, no. I do my tracing on a main board kindly donated by someone who bought a replacement main board, but we repaired his original board. This one has blown a second time MOSFETs, but we still might repair it. Anyway, it's not running. Mine and a friend's are later models that don't seem to have the TX6 circuit at all. 

Ah, that might answer something I've been wondering for a long time. I always thought that you could run an Axpert without a battery, at least to change settings or update firmware, if you powered it from either mains or solar. But I can't get that to work on my own machine. Maybe only the old models (circa 2013) could run off the mains / utility, and later models simply can't because the TX6 circuit has been left out. 

So @maxo, maybe that's yet another alternative : leave out TX6 altogether, and it might still work! Just like later models, you'll always need a battery connected to use the LCD screen or to do flash updates. 

2 hours ago, Coulomb said:

, maybe that's yet another alternative : leave out TX6 altogether, and it might still work! Just like later models, you'll always need a battery connected to use the LCD screen or to do flash updates. 

I also thought about that. It would probably mean a bit of battery discharge overnight (even when in bypass mode), but hopefully not too much. This is how my (much more expensive) inverter works too, the battery powers everything inside the box :-)

Hi Coulomb again

I do not know if your assumption to flash with new software will help or not to work without TX6 and it's souroundings.

My inverter works also just with battery (of coarse  only for a short period when it reached setup voltage to switch power output AC only from battery- on that time my setup was to charge the batery with 2Amp from grid, because the charge from PV was not able) and works also from grid to output AC household supply, but it does not see the PV supply and not charge the battery from PV supply - that was my reason to dissasemble and open the inverter. 

After oppening , my foundings are already known. 

I believe this SMPS with TX6 must work in my case , because when diode inside of U3 - optocoupler on SCC board activate CE output of U3 , then through connection cable SCC makes connection  between pins 1 and 2 on mainbord connector SCC and we get base supply voltage of Q9 through D74 and R276. If this happened, Q10 will conduct and provide power supply on leg 7 of the U10 =UC3845, then U10 provide PWM signal from leg 6 throug resistor R216 (10 OHM)  to gate of mosfet Q36 which drives TX9 ransformer on primary side. TX9 transformer then provide on secondary side all the voltages like could be seen from Figure 3 in Voltronic power service manuals.

That's my view of operation , please correct me if I'm wrong.

 

br

maxo

About the Plonkster view from battery supply

I agree, in all cases, when the grid is not present or even in cases when the battery is charged only from sun (type of setup work of the inverter), all internals are supplied from battery,  but how long - depends only of the Ah of the battery and their quality. It could happened, if the setup for AC out from battery shut off is for instance at 46V at the evening and if charge from grid is off, you have at the next morning just 45V or even less, if during the next day is cloudy or rainy, charge of the battery from sun is null or lousy, the battery voltage would drop additionally.
Once happend to me during the winter period, when we have snow on PV, the battery voltage has dropped below 36V and inverter stops work because of that- it was complettely dead , mean also bypass AC out from grid was off and LCD dispaly was dead too - blank.  After recharge the battery from outside charger to voltage when the inverter was in operation again and recharge the battery from grid - resetup of software to charge the battery from grid and from sun at the same time, charge from grid only with the smallest possible curent (2A) setup since then for a winter period. During the rest of season, charge only with sun is OK and good enough. During the sunny period, even in winter time period (February, March) and without snow on PV, the battery is fully charged alrady around 10 or 11AM (180Ah, 48V). 

So in case you want to charge the battery from grid, this internal charge system must work.

But in my case- fault  -like was written several times by me, inverter system does not recognize the sun and sun charger does not charge the battery at all, not provide the power through the inverter to AC out- with short words - the sun not exist at all for inverter. Because of that, my first estimation was the SCC board has problems, but when I opened the unit, the fault described in my first blog's was found.

 

maxo

 

I'm more of a hobbyist, but there is one thing I don't quite get. The whole circuit around TX6, that seems like stock standard SMPS, full bridge rectifier on the input (good ol' 1N4007, 1 amp 1000V), 450V smoothing cap, and then the high-frequency transformer with a current feedback loop that the 3845 chip uses to regulate the voltage. So what comes out on the other end (at AC_PS_OUT) is a square wave. Don't know the frequency, some SMPS chips vary the frequency as well as the duty cycle. This is then sent through two diodes, D62 and D58, and tied to the battery positive. I think the two diodes is probably to cause a 1.3V drop with a halfway tap, but that's neither here or there now, point is that is essentially a half-wave rectifier, so I assume there is another kind of smoothing cap that end (not included in the drawing), so that it's essentially just DC again. Basically, I'm asking whether this really needs to be a square wave or if DC will do fine. Because if DC will do fine, then find a replacement DC/DC converter of the correct voltage and wire it to D62 :-)

Something made by Tracopower perhaps... though it seems they are not cheap if you need anything above 50V :-)

9 hours ago, maxo said:

I believe this SMPS with TX6 must work in my case , because when diode inside of U3 - optocoupler on SCC board activate CE output of U3 , then through connection cable SCC makes connection  between pins 1 and 2 on mainbord connector SCC and we get base supply voltage of Q9 through D74 and R276. If this happened, Q10 will conduct and provide power supply on leg 7 of the U10 =UC3845, then U10 provide PWM signal from leg 6 throug resistor R216 (10 OHM)  to gate of mosfet Q36 which drives TX9 ransformer on primary side. TX9 transformer then provide on secondary side all the voltages like could be seen from Figure 3 in Voltronic power service manuals.

Yes, I believe that you have the power flow correct. I don't understand your comment "I believe this SMPS with TX6 must work in my case". Power for the control electronics can come from three sources: the battery, the utility, and the SCC. You have TX6 badly burned, so it can't be getting power through that. But that just means you need power from the battery to run the control electronics. (You can't use power from the SCC for other reasons.) I note that when utility charging at say 30 A, that doesn't come via the TX6 circuit; that's just a few watts to run the processor, LCD, and other control electronics. The 30 A comes through running the inverter in reverse (or effectively so). TX6 isn't needed for that; power can continue to come from TX9 where is usually comes from. When utility power is available, you can charge your battery from that source, as long as the inverter is in bypass mode.

I note that the primary power supply (with Q36 and TX9) can be turned off by the processor. I believe it does that when it senses the inverter switch is off, shuts down in an orderly manner, then activates opto U8 (which I recently added the the primary power supply traced schematic on AEVA), which will kill power to the processor itself.

It seems to me that you have two independent faults (likely both caused by the same event, but maybe not). One has burned the TX6 circuit, but you can survive without that (later models don't even have it), so that may have happened months ago and you did not notice it. The other is that the SCC fails to make its presence known to the main DSP, so it's as if the sun never shines. Somehow, the SCC is not talking to the main DSP, It could be because it is completely blown up and the SCC's processor doesn't have power, or it could be something on the inverter main board to do with comms to the SCC. There is a six or so pin connector between the processor daughter board and the SCC. Check that cable and any parts near it. There is a serial port on the main DSP that is dedicated to talking to the SCC's processor. They have to exchange commands for the SCC to be detected and charge the battery. Charge current is determined by the main DSP, not the SCC.

9 hours ago, maxo said:

So in case you want to charge the battery from grid, this internal charge system must work.

It seems to me that as long as you don't allow the battery to drop below 36 V, which is seriously low and very bad for the battery, and you have utility power or solar power available to keep it that way, then you can live without the TX6 power supply. But if you want to replace it, Plonkster's idea of using a DC power supply via D62 should work fine, as long as you can supply fifty odd volts at low current (100 mA or 5W should be plenty at a guess).

Can anyone recommend a good repair center where I can take a 4Kw Axpert Inverter for repairs.

The Inverter just started to do continues resets when input power is connected, and if I disconnect all power from inverter (input and output), and only have battery power connected to inverter (although battery is fully charged), then the inverter switch off completely.

Hi all, does anybody know where I can find a few of the new 5kW Axpert inverters?  My supplier messed up and now I have a bit of a problem... I have installed about 6 of these in the last weeks but have run out and next shipment is only coming in late September.

There must be other companies importing them directly.

thanks in advance.

PS: It can even be the not so new 4kW version but with with 4kW MPPT (no heatsink on top) as we can just upgrade the software to get to the 5kW version.  There is no physical difference.

2 hours ago, Hannes7212 said:

Hi all, does anybody know where I can find a few of the new 5kW Axpert inverters?  My supplier messed up and now I have a bit of a problem... I have installed about 6 of these in the last weeks but have run out and next shipment is only coming in late September.

There must be other companies importing them directly.

thanks in advance.

 

Perhaps try Maximum_solar on Ebay:

http://m.ebay.com/itm/Solar-power-inverter-5000w-48v-230vac-MPPT-solar-charger-80A-battery-charger-/162509114133

Edit: oops! The shipping mentions every land continent except Africa. But it may still be worth an enquiry. 

Edited August 25, 20178 yr by Coulomb

They do send it over here but you must arrange the shipping with them. I bought four Axperts from them and the shipping was very cheap. If you use them expect some "benefits"

Hi 

As an oldie of 80, I'm nnew to ths blog buisiness, but I urgently need informed advice.from you guys in the know how division.  I installed a 4kW AXPERT Inverter linked to my PAYG Eskom meter aboout two years ago.. The system worked very well until now. I will have to send the Inverter charger in for repairs after an explosion sounding like a gunshot occurred inside the Inverter during switchover to the pass through mode .Consumption monitored in this setup was set not exceed 4 k W. 

I set the system to BPU mode which which worked extremely well for me, particularly at night time, resulting in the pass through facility kicking in timeously when needed.. During the day I only used  solar and battery power by switching of the utility power altogether , consumption monitored ( effergy monitor. )!not to exceed 3.0 k W.

Periferals to AXPERT.

10 x 360  W  mono-crystalline solar panels.

12 x 110 A/ Gel based batterie ( 330 A/h ) 

I suspect sometng blew up in the D.C. To D.C. Charging unit as small fragments were found there. There seems to be no further physical damage in either the utility charger or the Inverter self, well as the Mosfett and MPPT's.

 Thank you.

 

Questions. 

What could possibly have caused the disfunction ??

where can I have this inverter adequately repaired by experts at a reasonable price.

2 hours ago, Des said:

I suspect sometng blew up in the D.C. To D.C. Charging unit as small fragments were found there. There seems to be no further physical damage in either the utility charger or the Inverter self, well as the Mosfett and MPPT's.

There have been some blow-ups in Australia, which we've attributed to the relatively low life ratings of the capacitors in the battery-side DC-DC converter (not the MPPT charger). Some of us, myself included, have pre-emptively replaced all the MOSFETs with 100 V models (up from 75 V and lately 80 V), and replacing the 2000 hour capacitors with 80 V 10,000 hour models (some were only rated at 63 V). But we've so far ignored the MPTT charger. 

http://forums.aeva.asn.au/viewtopic.php?p=64358#p64358

Are you sure all the devices (MOSFETs and IGBTs) on the main board heatsinks are ok? Usually if they blow up, there are cracks or stains from the smoke coming out. You will need to either take out the main board (a lot of work and not recommended), or use a light and mirror to see them all. It's possible that after a gunshot type failure (usually caused by electrical shoot-through), fragments from the main board could end up in the SCC (Solar Charge Controller). The SCC board isn't too hard to remove (the only trick is that there is no need to remove 4 screws securing the heatsinks, but no harm is done if you do), and it should be obvious whether the MPPT MOSFETs have failed. If the SCC has failed, it can be left out and the rest of the inverter should power up ok (I'd check the battery terminals for short circuit first, though the reverse battery protection circuit might mask a short circuit of the battery-side MOSFETs). That should give you confidence that the repair should not be too expensive.

[ Edit: the 4 screws securing the heatsinks are near the end of the long SCC board near the PV input terminal. ]

[ Edit: I'm assuming you have the more modern type with a long SCC board on top of the main board. Older ones have all the electronics at the top, and they have a heatsink at the top of the Axpert visible from the outside. ]

As for repairs, I don't know the situation in South Africa. It may well be better to buy a replacement SCC board if possible, and either install it yourself or get someone to install it for you. From Australia, I'd order a replacement from Maximum_solar on Ebay, but as noted in recent posts, this may not be straightforward. 

As a point of interest, would the Axpert have gotten more than average heat? Perhaps in the sun for some hours of the day? Heat seems to be the enemy of the capacitors involved.

I hope that your Axpert will be running again soon. 

10 hours ago, Des said:

explosion sounding like a gunshot

I remember blowing up a LM7812 once, by exceeding the max input voltage. It does sound like a gunshot and small pieces of plastic does fly through the air. I remember doing the same thing to a TIP3055 back in the day, we thought it should be okay since the voltage was nice and high and we were only going to be using 36V... forgetting that it is a fluorescent lamp with a nice big inductor that we are driving! :-)

Edit: Man, it's all coming back to me. The TIP3055 was a favourite in high school, but it only had a 60V rating. The lamp we were repairing was taken out by lightning and other than a few capacitors and the inductor, the only active component was a power transistor, and this was also what blew up. We couldn't make out the text on the front, and we didn't have one in the same form factor, but while testing on the highest voltage we had in the school lab (24 volts), the TIP3055 worked fine... while it lasted! We eventually swapped it for a TIP41C (100V) and that worked perfectly. Just shows you again, voltage ripple and steering too close to the maximum voltage... recipe for disaster :-)

(No, we didn't have oscilloscopes... we pretty much hacked it until it worked).

On 9/1/2017 at 12:55 AM, Coulomb said:

There have been some blow-ups in Australia, which we've attributed to the relatively low life ratings of the capacitors in the battery-side DC-DC converter (not the MPPT charger). Some of us, myself included, have pre-emptively replaced all the MOSFETs with 100 V models (up from 75 V and lately 80 V), and replacing the 2000 hour capacitors with 80 V 10,000 hour models (some were only rated at 63 V). But we've so far ignored the MPTT charger. 

http://forums.aeva.asn.au/viewtopic.php?p=64358#p64358

Are you sure all the devices (MOSFETs and IGBTs) on the main board heatsinks are ok? Usually if they blow up, there are cracks or stains from the smoke coming out. You will need to either take out the main board (a lot of work and not recommended), or use a light and mirror to see them all. It's possible that after a gunshot type failure (usually caused by electrical shoot-through), fragments from the main board could end up in the SCC (Solar Charge Controller). The SCC board isn't too hard to remove (the only trick is that there is no need to remove 4 screws securing the heatsinks, but no harm is done if you do), and it should be obvious whether the MPPT MOSFETs have failed. If the SCC has failed, it can be left out and the rest of the inverter should power up ok (I'd check the battery terminals for short circuit first, though the reverse battery protection circuit might mask a short circuit of the battery-side MOSFETs). That should give you confidence that the repair should not be too expensive.

[ Edit: the 4 screws securing the heatsinks are near the end of the long SCC board near the PV input terminal. ]

[ Edit: I'm assuming you have the more modern type with a long SCC board on top of the main board. Older ones have all the electronics at the top, and they have a heatsink at the top of the Axpert visible from the outside. ]

As for repairs, I don't know the situation in South Africa. It may well be better to buy a replacement SCC board if possible, and either install it yourself or get someone to install it for you. From Australia, I'd order a replacement from Maximum_solar on Ebay, but as noted in recent posts, this may not be straightforward. 

As a point of interest, would the Axpert have gotten more than average heat? Perhaps in the sun for some hours of the day? Heat seems to be the enemy of the capacitors involved.

I hope that your Axpert will be running again soon. 

Hi Colomb.

Thankyou for your very informative reply some days ago.

Trying to work out the Axperts architecture I've come to the conclusion that the machine basically consists out of three major modules, i.e.,  (1.) Main or mother board incorporating the actual inverter itself.

        ( 2.) MPPT Solar Charger.

        ( 3 ) AC mains Charger. 

On a further inspection I found that the Main boards left hand heatsink housing the ( switching ) transistors ( mosfets or thyristors ?)rated

40TPS 12 A rated at 55A 1200V to 247 AC.) 5 of the  9 blew up during the gunshot blast. 

On a closer inspection, I found no more physical damage on the three components listed above (cracks, some stains or heat damage. )  I

intend to replace them first to repair the damage.

Do you have any ideas as what simple tests I can perform to test the thee circuits before fireing the Axpert up again. 

The cost of a new motherboard  and installation llocally amounts to +- 60 % of a new machine and sounds exorbitant to me .

Thank you for your advice in anticipation.

 

3 hours ago, Des said:

mosfets or thyristors ?

The big power switching thins inside inverters are usually either MOSFETs or IGBTs :-)

3 hours ago, Des said:

Do you have any ideas as what simple tests I can perform to test the thee circuits before fireing the Axpert up again. 

There is a manual on this site under the download files with specifications of what various things must measure with a multimeter. That's a good starting point. I think the consensus is that if one FET is damaged, rather replace them all.

Thank you Plonckster 

i agree that replacing the  40TPS 12 A 's  all will be the better option.

Would the manual with the download files be found under the Axperts Service manual or the users manual..?

Thank you.

Yes but you need something like 15 posts before you can download - swing around the forum and post under a couple of topics that interest you then head to downloads...

12 hours ago, Des said:

I've come to the conclusion that the machine basically consists out of three major modules, i.e.,  (1.) Main or mother board incorporating the actual inverter itself.

        ( 2.) MPPT Solar Charger.

        ( 3 ) AC mains Charger. 

Actually, in the 4 kW Axperts, there are really only 2 modules, unless you count the processor daughter board as a third. The AC mains charger is actually the inverter run in reverse, so the power flow is from the AC input (connected to the AC output when AC charging) to the battery. In lower power models, I believe that there is a separate AC charger. In some Axperts, there is a power transformer that is part of a voltage regulator, which can look like an AC power supply.

On a further inspection I found that the Main boards left hand heatsink housing the ( switching ) transistors ( mosfets or thyristors ?)

On the heatsink that is not on the edge, they are all IGBTs or diodes. Four are for the full bridge at the higher voltage end of the DC-DC converter, one (two on some models) are for the buck converter, and four are for the 230 V inverter full bridge.

[quote[ 5 of the  9 blew up during the gunshot blast. [/quote]

We have a tentative theory that it's possible for the capacitors on the battery side of the DC-DC converter to go high impedance with age and heat, and this can cause transients on the DC bus (the 400-500 V bus), which can blow up the IGBTs. But it's far from certain. Even so, having opened up the inverter, it would seem wise to replace those capacitors.

As a point of interest, which ones blew up?

On a closer inspection, I found no more physical damage on the three components listed above (cracks, some stains or heat damage. )  

Hopefully that includes inspection of the battery-side MOSFETs. The problem is that usually the gates sort to collector and/or emitter, so you often blow up parts in the gate drivers. See below.

I intend to replace them first to repair the damage.

It may be better to leave the replacements out until you test the gate drivers when powered up. But that's pretty advanced, and we haven't figured out all the details, unfortunately. If you want to to attempt this, see this post.

Do you have any ideas as what simple tests I can perform to test the thee circuits before fireing the Axpert up again.

You should as far as possible test all the gate driver components:

for the higher voltage full bridge of the DC-DC converter (looks like we haven't traced those yet, but from poor memory they are pretty simple)

for the buck converter (similar to the below, I believe)

and/or for the 230 V inverter

but of course only the gate drivers for the sections where the IGBTs failed shorted to gate.

Be aware that it's possible to think you have fixed the gate drivers, put it all back together, and have it fail again. That seems to be more of a hazard for the battery side MOSFETs, whose drivers are more complex, but it's still something to be aware of.

The cost of a new motherboard  and installation locally amounts to +- 60 % of a new machine and sounds exorbitant to me .

It could well be ~60% of the cost of a new inverter.