July 30, 20232 yr Author 9 minutes ago, jumper said: Thanks @BritishRacingGreen, I had exactly the same 120V battery voltage fault on my old 5kVA clone. I think it was caused by running my panels in 3S with 136.6Voc. It would always trigger the error in the evening or early morning when the PV was switching on and off in low light and cold temps, so i figured it was the panels. At the time I was told it was probably my gel batteries because "the plates can bend and short circuit causing high voltages" which turned out to be a load of hogwash causing me to waste another 22k on a new lithium battery. Could high pv voltages cause this failure at all or would that be more likely to fry the mppt board? Hi Jumper, I cannot relate on face value how MPPT failure can actually cause disturbance on the - 12v rail. I am going to investigate further and report on this site. But I can confirm in no uncertain terms that the 120v reading does not relate at all to an actual battery high voltage. Its purely a measurement error due to the low or missing - 12v rail supply. I have in fact proved yesterday that when i disconnect the - 12v by unsoldering , that the error 03 appears with a battery voltage of 120v displayed on startup. Your high MPPT voltage could have caused strain/stress on the MPPT itself, but I cannot relate that to the - 12v rail failure I experienced.
July 30, 20232 yr Author 14 hours ago, BritishRacingGreen said: A number of members have already mentioned that their inverters display the value 120V for the battery , some permanently , others at times. Please if you experience this , switch that inverter off and get it fixed. I was on the receiving end today of a catastrophic failure . I have been requested by a member to check out a faulty 5kW Axpert clone inverter that displays the value of 120V for the battery voltage. The inverter raises the error 03 (battery voltage too high) and of course switches off after a number of seconds. I looked forward to this repair as I am a bit tired of igbt/mosfet failures and driver repair , I mean how difficult can this one be ? @Coulomb has made on number of occasion mention of the measurement resistor strings that can and will go open circuit, So that was the first check . But all resistors is fine . I shorted the battery bus and measured 8 Mohm ( 4+4) on the 2 pins going into the DSP board. Fortunately I obtained a second DSP board from someone I know , but the same 120V and error 03. So logic instructed me to verify the 5V , 12V and -12V that feeds into the DSP. And guess what , the -12V read +1.23V ! Oh dear , I check on the -12V linear regulator (7912 type) and measured the same . Removed the 3 pin device , check for load resistance not shorted, and replaced with a new one. Switched on , and the inverter was fine , producing 220VAC from my current limited PSU , no grid , no PV. Voltage reading on display matches the actual 'battery' voltage. This was way too easy , and while I was satisfied with the quick fix , I was worried why a supply line could go faulty like that ? , without a short circuit on its load output . I am so use by now that when I bring up a 5kW Axpert via PSU , the device draw just short of 1A at 52V VDC when it start inverting 220VAC output , no load. And same here , no excess power requirement. So I decided to let the machine burn-in and I kept it on . The 7912 gets warm on its little heat sink , but I recall this as typical. After 20 minutes I was so confident that I posted a nice whatsapp to member with display image , showing his machine in operation. After about an hour I decided to switch off , and back on , just for the good order. Perfect , but after a couple of minutes the machine suddenly died silently , fortunately without an explosion , but the PSU went into hard current limiting mode. Short on the battery bus. 3 x MOSFET short circuit , 5 x IGBT short circuit . some drivers gate resistors blown open circuit Wow !!! Turns out that this -12V supply of ours might not be as mission critical as the 5V and 12V , but it feeds the 3525 PWM controller ic , which in turn drives the mosfets and the battery side igbts. The problem is it does not feed the circuit on its own , but is combined with the 12V in order to affectively provide a 24V supply for the 3525 . This is somewhat nasty in that should the -12V fail with a reasonably low impedance wrt to GND , the 12V rail can still power the 3525 , but at out of spec conditions. I am of the opinion that either the 3525 or its load circuits was failing , causing the -12V to sag . Meanwhile this same -12V is used on the DSP to power one side of the measurement op-amp , this causes a so called high battery voltage , and the DSP fortunately switches off, albeit all for the wrong reason. So the second time this rail failed while the inverter was inverting , it was less forgiving , it destroyed the power mosfets and igbts. Here I am of the opinion that the failure mode of the -12V caused the 3525 to limp with the +12V , but the out of spec pulses to the mosfets was non-deterministic . It turned the mosfets on at the wrong times , or unable to turn them off in good time. Note that if the -12V regulator is already damaged , there will not be catastrophic failure on startup. This is because error 03 will be generated before the DSP enables the 3525 PWM ic. So on face value this looks like a simple fault on the measurement side , but the catastrophic failure is hidden and abstracted from us , until you 'rectify' the 'fault' . Very unforgiving. Repairing of high power Inverters is not for everyone. It can break your spirit at times. Will investigate whether this failure is viable to repair , but that is for another day. This failure calls for a method not unlike the first MAX I repaired. You need to power the system rail supplies and test the mosfet and igbt drivers meticulously without any battery or grid or pv power. On the Max its easy, there is an external SPS supply that you substitute with your own 60v input. This will then power up the system smps. On the older 5kw axperts its not that easy. The smps is powered directly from the battery, and one will actually have to make a nice pcb track cut in order to inject external power.
August 1, 20232 yr Author a Short Guide to Bring Up a 5kW Axpert Main Board in the Softest Possible Manner : Chapter 1 The reasonable amount of success I enjoyed repairing the MAX range of inverter is because of using a methodology to power the system supplies of the board , and debug the critical sections like mosfet and igbt drivers , without powering the actual power chain . This means zero voltage on the battery bus , zero voltage on the high voltage DC bus , no grid , no pv. The max has actually an external system supply connector which makes this feasible. The 5kW boards does not have this option , but we have devised a non-intrusive way of injecting raw dc for the system supply SMPS. The reason why this bare minimum soft method of powering the system is important , is it allows you to debug all the Mosfet and IGBT drivers without the risk of blowing those very expensive Mosfets and IGBTs . You can now test the circuit in a very controlled and safe environment. So the idea is that you remove the main board and remove ALL external interfaces . That includes the DSP controller board, the MPPT board , the fans , the comm modules . In the end you are left with just the bare main board. Prerequisite The only initial condition required , is that the battery bus , the high voltage dc bus and the ac output bus have no short circuits . These conditions you can verify by checking with multimeter. if there are shorts you need to check the mosfets and igbts for failures by isolating them. You dont have to substitute them yet with new transistor , but you need to remove faulty ones. Refer to Voltronics service manual which will guide you thru resistive tests in order to verify the typical resistances required. We are currently only interested that the gate to source are not shorted , because that will prevent us to test the gate driver signals later on the exercise. In the case of IGBTS this is gate to emitter. Also read the resistance of 12V,-12V and 5V rails to GND. with the 12v and 5v the capicitors will see to it that the resistance gradually increase . The 5V will easily reach >10k , the 12V >50k , but the -12V will be reasonable steady at at about 450 ohms. Once your board has no bus related short circuits , we are good to go in order to bring up the main supply. Powering the up the Main SMPS So we going to inject external controlled power to the input of the SMPS . You will need a current limited 30V dc power supply , but you will need a minimum of 30V. The voltage may be as high as 55VDC , but we will stay with 30V for safety reasons. Limit the maximum current of the power supply to 200mA . We going to draw about 100mA if the board powers up 'nicely'. The SMPS is normally supplied by the battery input . However we don't want to apply power to the battery terminals, so we inject our 30V supply as follows. Notice below that there is a 2-pin SCC connector . Next to it is a 2-pin AC-START connector . You must connect your 30V positive terminal on pin 2 of SCC connector. Doing so allow us to inject voltage on the SMPS input feed , but D53 will block the voltage reaching the battery positive , or CH+ as depicted in the schematic. Now we are left with connecting the negative of our 30V supply to the negative CH- rail. Note that you cannot connect it onto the battery negative terminal , because some boards have reverse polarity mosfets that will not be biased , so we need to connect to the CH- rail . A convenient way of doing so is to locate to upright metal spacers , which is labelled CHG+ and CHG- (or CH+/CH- as per schematic) . I have tied my power supply negative conveniently to this metal spacer. Once you have connected and powered on your power supply , you will notice that no current is drawn. That is because you must start the SMPS manually. This is what the AC-START 2-pn connector is there for. You can either connect the inverter on-off switch here , or you can merely temporarily short out the 2 terminal for 2 seconds or so. If all goes well you will notice the power supply is delivering about 100mA of current to the SMPS . We can now check the 5V , 12V and -12V rail voltages . The 5V should be very close to 5.0V , 100mV either way is ok. 12V should be from 11.85V upwards but not exceeding 12.4V . Same for -12V (-11.8 to -12.4) I will post again as chapter 2 of this post . .... to be continued ....
August 5, 20232 yr On 2023/07/21 at 9:01 AM, Coulomb said: Oh. Well that could explain it. If the bus soft start power supply is located on the solar charger, then it will generate high voltage from the battery, and the DSP will stop it when the voltage it measures on the bus is high enough. But if you cut that connection, then it would not know when to stop, and the bus soft start power supply could apply excessive voltage to the solar charger circuit. The voltage would also rise very quickly without the bus capacitors to slow it down. On all models that I'm familiar with, the bus soft start power supply is located on the main board, not the solar charger board. I think that MAX models have two power supplies on a smallish printed circuit that is attached to the solar charger board; one of these may be the bus soft start circuit. Though I can't think why they'd do that. i am happy you now explain to me why diode on mppt and igbt failed lets recap all story for new comers so that my reply to you be understandable to others inverter come in with all igbts goood all fets bad i removed all fets and power it up i gooterror 09 it was ok to get 09 since all fets out of circuit but for me it was not ok why i should not get any momentry pulses and tried to follow why cpu not turn the mosfets by sending signal and failed i then removed all igbts and turn the device on i get momentary primary side pulsesand error 52 ok now its better however when i fited all fets i get error 09 again end up with inverter that is all ok and i have no output i removed the fets again now since i tested all things 12vdc minus 12 5 5.6vdc 18.vdc coplers resistor diode in priamry and seocndery i decided to change the 500vdc caps i was lazy so i told my self why not to seperate the inveryer board from mppt which might seperate the bad cap and that was bad idea since soft start is in the mppt board , and will work indefinatley , since cpu turn it on and with no voltage on the bus of the inverter the soft start will incvrease the voltage so high and blow mppt diode and mppt igbt probably because the measuring is done across the inverter 500vdc cap not the mppt caps after i replaced all bad diode in mppt and igbt and repalced the cap, and soldered all fets the inverter works nicely mission done بfirst i replaced the cap with new 400vdc for testing once the device work fine i get large 450 vdc 470 mf and replaced both large caps the inverter works fine since then thanks colom for showing me why actually the diode and the igbt in the mppt failed Edited August 5, 20232 yr by wael_fathe
August 5, 20232 yr On 2023/08/01 at 6:13 PM, BritishRacingGreen said: a Short Guide to Bring Up a 5kW Axpert Main Board in the Softest Possible Manner : Chapter 1 The reasonable amount of success I enjoyed repairing the MAX range of inverter is because of using a methodology to power the system supplies of the board , and debug the critical sections like mosfet and igbt drivers , without powering the actual power chain . This means zero voltage on the battery bus , zero voltage on the high voltage DC bus , no grid , no pv. The max has actually an external system supply connector which makes this feasible. The 5kW boards does not have this option , but we have devised a non-intrusive way of injecting raw dc for the system supply SMPS. The reason why this bare minimum soft method of powering the system is important , is it allows you to debug all the Mosfet and IGBT drivers without the risk of blowing those very expensive Mosfets and IGBTs . You can now test the circuit in a very controlled and safe environment. So the idea is that you remove the main board and remove ALL external interfaces . That includes the DSP controller board, the MPPT board , the fans , the comm modules . In the end you are left with just the bare main board. Prerequisite The only initial condition required , is that the battery bus , the high voltage dc bus and the ac output bus have no short circuits . These conditions you can verify by checking with multimeter. if there are shorts you need to check the mosfets and igbts for failures by isolating them. You dont have to substitute them yet with new transistor , but you need to remove faulty ones. Refer to Voltronics service manual which will guide you thru resistive tests in order to verify the typical resistances required. We are currently only interested that the gate to source are not shorted , because that will prevent us to test the gate driver signals later on the exercise. In the case of IGBTS this is gate to emitter. Also read the resistance of 12V,-12V and 5V rails to GND. with the 12v and 5v the capicitors will see to it that the resistance gradually increase . The 5V will easily reach >10k , the 12V >50k , but the -12V will be reasonable steady at at about 450 ohms. Once your board has no bus related short circuits , we are good to go in order to bring up the main supply. Powering the up the Main SMPS So we going to inject external controlled power to the input of the SMPS . You will need a current limited 30V dc power supply , but you will need a minimum of 30V. The voltage may be as high as 55VDC , but we will stay with 30V for safety reasons. Limit the maximum current of the power supply to 200mA . We going to draw about 100mA if the board powers up 'nicely'. The SMPS is normally supplied by the battery input . However we don't want to apply power to the battery terminals, so we inject our 30V supply as follows. Notice below that there is a 2-pin SCC connector . Next to it is a 2-pin AC-START connector . You must connect your 30V positive terminal on pin 2 of SCC connector. Doing so allow us to inject voltage on the SMPS input feed , but D53 will block the voltage reaching the battery positive , or CH+ as depicted in the schematic. Now we are left with connecting the negative of our 30V supply to the negative CH- rail. Note that you cannot connect it onto the battery negative terminal , because some boards have reverse polarity mosfets that will not be biased , so we need to connect to the CH- rail . A convenient way of doing so is to locate to upright metal spacers , which is labelled CHG+ and CHG- (or CH+/CH- as per schematic) . I have tied my power supply negative conveniently to this metal spacer. Once you have connected and powered on your power supply , you will notice that no current is drawn. That is because you must start the SMPS manually. This is what the AC-START 2-pn connector is there for. You can either connect the inverter on-off switch here , or you can merely temporarily short out the 2 terminal for 2 seconds or so. If all goes well you will notice the power supply is delivering about 100mA of current to the SMPS . We can now check the 5V , 12V and -12V rail voltages . The 5V should be very close to 5.0V , 100mV either way is ok. 12V should be from 11.85V upwards but not exceeding 12.4V . Same for -12V (-11.8 to -12.4) I will post again as chapter 2 of this post . .... to be continued .... There is no substitute for knowing your ABC 😀😀
August 7, 20232 yr @Coulomb few important quesions mr colombs hope y answer them will the igbt buck stuck on when inverter works because it have no rule as its only rule is in charging cycle or they some how rely on the bult in diode to "pass" the igbt ? how can we ramp up the inverter slowly increasing the voltages acorss the 450 bus voltage when it is already ramped up to 400vdc by the soft start circuit ? so do you think there is not inverter soft start due to the soft start circuit? today i recived 100 pces igbt 40q60 alas they have no built in diode big lose for me ...i will try to fix this by installing external diode will it work?what is diode specs i should use? how can i turn 2 wire fan to 3 wire fan or at least let the cpu accept 2 wired fan because we inject speed report wire fake one ofcourse ,,,,,we let cpu think that fan is doing good all the time ? can 4 wired fan be used instead of 3 we just have to ignore the wire that controls the speed and leave the one that reports the speed?
August 8, 20232 yr On 2023/08/08 at 9:30 AM, wael_fathe said: will the igbt buck stuck on when inverter works I believe so. In the firmware, the buck controller can be in one of three states: off, PWMing, or always on. However, if something else is pushing the bus voltage more than 20 V higher than the transformed battery voltage (i.e. there is more than 20 V across the buck transistor), it is not turned on. On 2023/08/08 at 9:30 AM, wael_fathe said: how can we ramp up the inverter slowly increasing the voltages across the 450 bus voltage when it is already ramped up to 400vdc by the soft start circuit ? The bus soft start power supply is relatively weak, so it takes a second or two to ramp the bus voltage up. Once it reaches a certain level, the DSP should switch it off, and it should take no further part in determining the bus voltage. Other power sources (the DC-DC, the inverter running backwards, or the high PV voltage solar charger if present) all have much higher power than the soft start power supply, and will therefore influence the bus voltage much more strongly. On 2023/08/08 at 9:30 AM, wael_fathe said: today i recived 100 pces igbt 40q60 alas they have no built in diode big lose for me ...i will try to fix this by installing external diode will it work?what is diode specs i should use? I thought that MOSFETs (but not IGBTs) all have inherent diodes, so maybe you don't need anything external. But I'm no expert on this; research carefully. If you do need the diodes, I would be very hesitant about using external ones when the board is not designed to accommodate them. These diodes do a very important job, and layout is critical. There isn't a lot of voltage margin with factory parts as it is. These diodes need to be high speed and very high current. [ Edit: Sigh. I misread the original poster, who clearly said IGBTs. All IGBTs require diodes, either built-in or external. ] On 2023/08/08 at 9:30 AM, wael_fathe said: can 4 wired fan be used instead of 3 we just have to ignore the wire that controls the speed and leave the one that reports the speed? I believe so, sorry, I've not played much with fans. Edited August 10, 20232 yr by Coulomb
August 8, 20232 yr 16 hours ago, Coulomb said: There isn't a lot of voltage margin with factory parts as it is. These diodes need to be high speed and very high current. I believe so, sorry, I've not played much with fans. so i guess that 1200vdc 30a high speed diode will be more than suffeinct but will they be heating the diodes not need to be heat sinked i guess ? back in old good days of crt repair horizontal output transistor come in 2 flavors one with diode bult in one wit out the one without have an external diode i wonder if we can do the same for inverters
August 9, 20232 yr i guess that 1200vdc 30a high speed diode will be more than sufficient [ Edit: I don't know why I was thinking MOSFETs instead of IGBTs, sigh. I don't even think that you can make MOSFETs without diodes. ] I would think that IF you used one per MOSFET (not one per 4 paralleled MOSFET), that would be barely sufficient. My understanding is that these diodes have to carry the full load current for short periods of time. I don't know if you can get away with using average current instead of peak current, and I don't know if they will need heat sinking or not. As I say, I don't think it's a good idea. The 1200 V rating is way more than you need (which is about 100 V). back in old good days of crt repair horizontal output transistor come in 2 flavors one with diode bult in one without the one without have an external diode The difference is that the models with the external diodes would be designed with thick PCB tracks of suitably low inductance, and the diode would be appropriately heat sunk if necessary. Here you would be tacking diodes under the PCB, with untested wires of unknown resistance and inductance, and probably no heat sinking. Edited October 2, 20232 yr by Coulomb
August 9, 20232 yr 20 hours ago, Coulomb said: IIF you used one per MOSFET (not one per 4 paralleled MOSFET), i have no problem with my mosfet i have problem with output igbts for h bridge i got 100 pces from china they lack the diodes , ------------ That's too easy; the DSP arranges the phase so that power flows from the DC bus towards the load. If the load increases or decreases by 1 kW, that's no problem, the grid instantaneously supplies the difference. That's Kirchoff's law, so it's instantaneous, and the DSP doesn't even have to make any changes, just keep that 2 kW chugging out to the load. THIS was your reply to britshgreen racing sorry to re-asking... but if the solar dc fed to the high dc bus and turned into ac 220ac and even maybe get synched with the utility ac interms of amplitude frequency and phase now both (solar generated ac ) utility genertaed ac in complete synch how cpu can source power from one source and omit the other or how can source a load with controlled power mixing say 20 percent from solar 80 from utilty to me if all waveforms are in complete synch there we cant instruct one to provide and other not 2 they should alwyas do 50percent power for the load ? Edited August 9, 20232 yr by wael_fathe
August 10, 20232 yr 14 hours ago, wael_fathe said: the DSP arranges the phase so that power flows from the DC bus towards the load. If the load increases or decreases by 1 kW, that's no problem, the grid instantaneously supplies the difference. That's Kirchoff's law, so it's instantaneous, Certainly Kirchoff's law is always obeyed, but I don't think it applies in this instance. Consider the inverter connected to an ideal AC source/sink via an inductor (the L of the LC filter). Phase is arranged to be equal to the source/sink. Amplitude and phase can be adjusted by the DSP. If the amplitude and phase are the same, then there is no voltage across the inductor, and no current flows. Now let's change the phase by 1°, keeping the same amplitude. You now have two vectors (representing the AC output of the inverter and the source/sink), which are the same amplitude but slightly different phase. The difference between these vectors is the voltage across the inductor. The vector representing the inductor voltage will be small, and will be very close to 90° with respect to the other two vectors (there will be a long, thin triangle). Current through the inductor will be very close to 90° out of phase with the voltage, so the inductor's current, and therefore the current to/from the source/sink, will be in phase with the voltage. So the power flow will be close to unity power factor. Depending on whether the phase is leading or lagging with respect to the source/sink, power flow will be from the DC bus towards the load, or the other way around. Consider if we changed the amplitude and kept the phase angle zero; the triangle now has almost no area, and the inductor voltage is almost parallel to the other vectors. So now the current will be 90° out of phase with the source/sink, so the power flow will be almost entirely reactive. Whether the power flow is inductive or capacitive depends on whether the inverter amplitude is greater or less than that of the source/sink. So the power magnitude can be adjusted by the phase of the inverter relative to the source/sink, and the power factor can be adjusted with the amplitude. So you have complete control over P and Q (real and imaginary power respectively). If you screw up and don't adjust properly to the instantaneous power flows (required battery charging current and/or load), then net power flows into or out of the DC bus, causing the bus capacitors to be charged or discharged respectively. They are biggish capacitors, but even so with several amps of current for each kilowatt of power, the bus voltage will rapidly go too high or too low. So the DSP is constantly battling to keep the DC bus voltage within reasonable bounds. Plus, when the DC-DC converter is running, you effectively have the battery voltage transformed across the DC bus. When this is the case, things are a bit easier, but any errors will result in wrong values of battery charge or discharge current. It's pretty nifty what it all does. 14 hours ago, wael_fathe said: how cpu can source power from one source and omit the other or how can source a load with controlled power mixing say 20 percent from solar 80 from utilty It's done by careful adjustment of the inverter's phase relative to the grid. Amplitude is adjusted to make the grid load close to unity. And this adjustment is made thousands of times per second.
August 13, 20232 yr Author On 2023/08/01 at 6:13 PM, BritishRacingGreen said: a Short Guide to Bring Up a 5kW Axpert Main Board in the Softest Possible Manner : Chapter 1 The reasonable amount of success I enjoyed repairing the MAX range of inverter is because of using a methodology to power the system supplies of the board , and debug the critical sections like mosfet and igbt drivers , without powering the actual power chain . This means zero voltage on the battery bus , zero voltage on the high voltage DC bus , no grid , no pv. The max has actually an external system supply connector which makes this feasible. The 5kW boards does not have this option , but we have devised a non-intrusive way of injecting raw dc for the system supply SMPS. The reason why this bare minimum soft method of powering the system is important , is it allows you to debug all the Mosfet and IGBT drivers without the risk of blowing those very expensive Mosfets and IGBTs . You can now test the circuit in a very controlled and safe environment. So the idea is that you remove the main board and remove ALL external interfaces . That includes the DSP controller board, the MPPT board , the fans , the comm modules . In the end you are left with just the bare main board. Prerequisite The only initial condition required , is that the battery bus , the high voltage dc bus and the ac output bus have no short circuits . These conditions you can verify by checking with multimeter. if there are shorts you need to check the mosfets and igbts for failures by isolating them. You dont have to substitute them yet with new transistor , but you need to remove faulty ones. Refer to Voltronics service manual which will guide you thru resistive tests in order to verify the typical resistances required. We are currently only interested that the gate to source are not shorted , because that will prevent us to test the gate driver signals later on the exercise. In the case of IGBTS this is gate to emitter. Also read the resistance of 12V,-12V and 5V rails to GND. with the 12v and 5v the capicitors will see to it that the resistance gradually increase . The 5V will easily reach >10k , the 12V >50k , but the -12V will be reasonable steady at at about 450 ohms. Once your board has no bus related short circuits , we are good to go in order to bring up the main supply. Powering the up the Main SMPS So we going to inject external controlled power to the input of the SMPS . You will need a current limited 30V dc power supply , but you will need a minimum of 30V. The voltage may be as high as 55VDC , but we will stay with 30V for safety reasons. Limit the maximum current of the power supply to 200mA . We going to draw about 100mA if the board powers up 'nicely'. The SMPS is normally supplied by the battery input . However we don't want to apply power to the battery terminals, so we inject our 30V supply as follows. Notice below that there is a 2-pin SCC connector . Next to it is a 2-pin AC-START connector . You must connect your 30V positive terminal on pin 2 of SCC connector. Doing so allow us to inject voltage on the SMPS input feed , but D53 will block the voltage reaching the battery positive , or CH+ as depicted in the schematic. Now we are left with connecting the negative of our 30V supply to the negative CH- rail. Note that you cannot connect it onto the battery negative terminal , because some boards have reverse polarity mosfets that will not be biased , so we need to connect to the CH- rail . A convenient way of doing so is to locate to upright metal spacers , which is labelled CHG+ and CHG- (or CH+/CH- as per schematic) . I have tied my power supply negative conveniently to this metal spacer. Once you have connected and powered on your power supply , you will notice that no current is drawn. That is because you must start the SMPS manually. This is what the AC-START 2-pn connector is there for. You can either connect the inverter on-off switch here , or you can merely temporarily short out the 2 terminal for 2 seconds or so. If all goes well you will notice the power supply is delivering about 100mA of current to the SMPS . We can now check the 5V , 12V and -12V rail voltages . The 5V should be very close to 5.0V , 100mV either way is ok. 12V should be from 11.85V upwards but not exceeding 12.4V . Same for -12V (-11.8 to -12.4) I will post again as chapter 2 of this post . .... to be continued .... a Short Guide to Bring Up a 5kW Axpert Main Board in the Softest Possible Manner : Chapter 2 I think I have discovered the failure mode of Axpert inverters giving F03 , F06 and other measurement related errors at random times. Especially those that displays exactly 120V for the battery voltage . In chapter 1 I have brought up a 5kW main board without the need of supplying anything on the battery terminals. This is our objective so we can investigate the system power supplies , mosfet and igbt drivers without the power chain being powered at all. I have discovered lately that there are a number of inverters that works otherwise , but would display error F03 (battery voltage too high) . I had one incoming in an earlier post where I discovered the F03 being affected exactly when the -12V supply rail is either very low or missing. I could actually simulate the condition by removing the -12V at will , and observe the error with 120V battery being displayed. It struck me this morning while discussing the problem with a friend in Cape Town that has the same problem driving him crazy, that this -12V rail could be suffering the same dried-out capacitors as we are by now aware of the affect that have on the 5V and +12V rails. Typically when these capacitors run dry , the 5V is mostly affected and that we see by the lcd display powering up and shutting down cyclically. When I repair these machines by replacing the capacitors , I also replace the -12V filter capacitor as a rule of thumb. However its possible that the -12V capacitor can run critically dry before the 5V one does. But the symptoms are now a bit complicated . The machine still works but the -12V will fail at random instances , causing errors like F03 and F06 . The friend in Cape Town also experiences F06 at times. So I revisited the 5kW main board I have with the faulty -12V rail , removed the filter capacitor , and tested the capacitance for starters . It is horrifically bad . not even 1uF for a 100uF rating. Below is my schematic of the MAX7.2 SMPS , but please note that the 5kW one is similar . I have highlighted the filtering capacitors as shown . For 5kW there is only one capacitor per rail. and C116 for 5kW is 100uF instead of the 470uF shown. So when you power up the main board as per my procedure , you are probably going to see a nice 5V,12V and -12V on your multi-meter. There is only a very small load so the 100nF in parallel with the electrolytic , e.g. C117, is sufficient to smooth the input. So you will have to clip on about a 12R 10W resistor on the -12V load output to draw at least a 1A current , then check the output voltage. Ideally an oscilloscope on the C116 should be used to check the ripple as well. My friend in Cape Town is going to open up his machine and replace C116 with a new one , and give us feedback as well. But I am very optimistic that this is the root cause of the inadvertent errors. EDIT : The reason why the -12V supply rail is affecting measurements of the DSP is due to the fact that this supply , along with others , is used to power/bias the instrumentation op amps on the the controller card. Also , when you test a main board that has a couple of years service , replace the filter capacitors as shown on the schematic with new ones as a rule of thumb . EDIT 2 : A couple of weeks ago I repaired a machine for a member that had the lcd power cycling problem , but he also experienced the F03 problem at times when the LCD (5V) decided to work for long periods. The machine had the classic problem of the 5V and 12V filter capacitors that ran nearly dried. But I have not only replaced them , but others as well , including C116. So I have 'inadvertently' also cleared the F03 120V battery voltage problem. Which explains why he now does not get measurement errors any more. Edit 3 : To summarize : It is unreal how super important the accuracy , performance and stability of your SMPS system supply rails are . It can also lead to expensive failures like mosfet and igbt destruction , I have first hand experience of that in my short little journey. Edited August 13, 20232 yr by BritishRacingGreen
August 19, 20232 yr On 2023/01/28 at 9:07 AM, BritishRacingGreen said: REPAIR : 4 x RCT MKS2 Inverters Received from Malawi Went to receive the boxes from Alrode destination as fast as my feet could fly. I will refer to the inverters as MR1,MR2,MR3 and MR4 . MR1 and MR2 had been paired as parallel units in a single location , MR2 and MR3 also paired but different location. The initial bringing up of the inverters done by current limited dc source on battery. MR4 : error code 09 . That's nasty , indicates IGBT and/or MOSFETS blown , but great opportunity for me to show my experienced gained in this regard Below is short video showing the symptoms of MR1, MR2. WhatsApp Video 2023-01-28 at 9.11.19 AM.mp4 1.31 MB · 0 downloads MR1,MR2 : You cannot believe this . Exact same problem as the previous Cape Town machine. Frequent clicking sound . Couldn't resist the temptation . Immediately disassembled , and powered the main board and control board standalone. Exact same problem . The input electrolytic capacitor on U5 (5V regulator) has given up on life. Temporary soldered on a 470uF and problem solved. Two exact machines in same location , same symptons , same remedy , crazy is it not ! Main boards marked 2015 . MR3 : This one has a major problem as far as I am concerned : it has no problem at all. So here comes the start of an issue regarding quantative vs qualitative measures. So if we cannot quantify an error , we will have to use qualitative measures to ensure this inverter is good for a number of years ahead, and that we can dispatch back to Malawi with a calculated measure of confidence . This also holds true really for MR1,MR2 and MR4. So all in all all four inverters appears to be serviceable and I am looking forward to start with MR4 and document the findings and repair. Hi I have the same symptoms on my inverter as your MR1. What is the voltage of the 470uf you replaced? thanks
August 19, 20232 yr Author 4 hours ago, marcomar said: Hi I have the same symptoms on my inverter as your MR1. What is the voltage of the 470uf you replaced? thanks I assume you referring to C116 . Interestingly I have had boards with 100uF 25V capacitor , others had 470uF 25V. I will recommend 470uF 25V for C116 , also 1000uF 25V for C78 and C78 . The higher voltage cap's footprint is a bit bigger , but you can still manage to squeeze then in. Note that all three capacitors must extended temperature range of 105 degrees Celsius . C78,C79 and C116 are kingpin. They are exposed to heave ripple current conditions , shortening their life even quicker. Apart from these 3 , I would also recommend that you replace C75 (47uF 25V) and C75 (47uF 25V) as well . Always check your existing values of caps you removed and if they are higher capacitance than the ones I stated here, upgrade to the higher value. The photo images with labels are courtesy of @Coulomb and comes in very handy. Edited August 19, 20232 yr by BritishRacingGreen
August 19, 20232 yr On 2023/07/29 at 10:30 AM, BritishRacingGreen said: A number of members have already mentioned that their inverters display the value 120V for the battery , some permanently , others at times. Please if you experience this , switch that inverter off and get it fixed. I was on the receiving end today of a catastrophic failure . I have been requested by a member to check out a faulty 5kW Axpert clone inverter that displays the value of 120V for the battery voltage. The inverter raises the error 03 (battery voltage too high) and of course switches off after a number of seconds. I looked forward to this repair as I am a bit tired of igbt/mosfet failures and driver repair , I mean how difficult can this one be ? @Coulomb has made on number of occasion mention of the measurement resistor strings that can and will go open circuit, So that was the first check . But all resistors is fine . I shorted the battery bus and measured 8 Mohm ( 4+4) on the 2 pins going into the DSP board. Fortunately I obtained a second DSP board from someone I know , but the same 120V and error 03. So logic instructed me to verify the 5V , 12V and -12V that feeds into the DSP. And guess what , the -12V read +1.23V ! Oh dear , I check on the -12V linear regulator (7912 type) and measured the same . Removed the 3 pin device , check for load resistance not shorted, and replaced with a new one. Switched on , and the inverter was fine , producing 220VAC from my current limited PSU , no grid , no PV. Voltage reading on display matches the actual 'battery' voltage. This was way too easy , and while I was satisfied with the quick fix , I was worried why a supply line could go faulty like that ? , without a short circuit on its load output . I am so use by now that when I bring up a 5kW Axpert via PSU , the device draw just short of 1A at 52V VDC when it start inverting 220VAC output , no load. And same here , no excess power requirement. So I decided to let the machine burn-in and I kept it on . The 7912 gets warm on its little heat sink , but I recall this as typical. After 20 minutes I was so confident that I posted a nice whatsapp to member with display image , showing his machine in operation. After about an hour I decided to switch off , and back on , just for the good order. Perfect , but after a couple of minutes the machine suddenly died silently , fortunately without an explosion , but the PSU went into hard current limiting mode. Short on the battery bus. 3 x MOSFET short circuit , 5 x IGBT short circuit . some drivers gate resistors blown open circuit Wow !!! Turns out that this -12V supply of ours might not be as mission critical as the 5V and 12V , but it feeds the 3525 PWM controller ic , which in turn drives the mosfets and the battery side igbts. The problem is it does not feed the circuit on its own , but is combined with the 12V in order to affectively provide a 24V supply for the 3525 . This is somewhat nasty in that should the -12V fail with a reasonably low impedance wrt to GND , the 12V rail can still power the 3525 , but at out of spec conditions. I am of the opinion that either the 3525 or its load circuits was failing , causing the -12V to sag . Meanwhile this same -12V is used on the DSP to power one side of the measurement op-amp , this causes a so called high battery voltage , and the DSP fortunately switches off, albeit all for the wrong reason. So the second time this rail failed while the inverter was inverting , it was less forgiving , it destroyed the power mosfets and igbts. Here I am of the opinion that the failure mode of the -12V caused the 3525 to limp with the +12V , but the out of spec pulses to the mosfets was non-deterministic . It turned the mosfets on at the wrong times , or unable to turn them off in good time. Note that if the -12V regulator is already damaged , there will not be catastrophic failure on startup. This is because error 03 will be generated before the DSP enables the 3525 PWM ic. So on face value this looks like a simple fault on the measurement side , but the catastrophic failure is hidden and abstracted from us , until you 'rectify' the 'fault' . Very unforgiving. Repairing of high power Inverters is not for everyone. It can break your spirit at times. Will investigate whether this failure is viable to repair , but that is for another day. On 2023/07/29 at 10:30 AM, BritishRacingGreen said: thanks for this explanation very informative notes
August 20, 20232 yr On 2023/08/19 at 7:34 PM, BritishRacingGreen said: I would also recommend that you replace C75 (47uF 25V) and C75 (47uF 25V) I'm guessing that one of those C75's should be something else; are the values correct as well? Perhaps you meant C95 on the 5 V rail, 100 μF 16 V or 25 V (you have 50 V there).
August 23, 20232 yr On 2023/08/10 at 6:05 AM, Coulomb said: Certainly Kirchoff's law is always obeyed, but I don't think it applies in this instance. Consider the inverter connected to an ideal AC source/sink via an inductor (the L of the LC filter). Phase is arranged to be equal to the source/sink. Amplitude and phase can be adjusted by the DSP. If the amplitude and phase are the same, then there is no voltage across the inductor, and no current flows. Now let's change the phase by 1°, keeping the same amplitude. You now have two vectors (representing the AC output of the inverter and the source/sink), which are the same amplitude but slightly different phase. The difference between these vectors is the voltage across the inductor. The vector representing the inductor voltage will be small, and will be very close to 90° with respect to the other two vectors (there will be a long, thin triangle). Current through the inductor will be very close to 90° out of phase with the voltage, so the inductor's current, and therefore the current to/from the source/sink, will be in phase with the voltage. So the power flow will be close to unity power factor. Depending on whether the phase is leading or lagging with respect to the source/sink, power flow will be from the DC bus towards the load, or the other way around. Consider if we changed the amplitude and kept the phase angle zero; the triangle now has almost no area, and the inductor voltage is almost parallel to the other vectors. So now the current will be 90° out of phase with the source/sink, so the power flow will be almost entirely reactive. Whether the power flow is inductive or capacitive depends on whether the inverter amplitude is greater or less than that of the source/sink. So the power magnitude can be adjusted by the phase of the inverter relative to the source/sink, and the power factor can be adjusted with the amplitude. So you have complete control over P and Q (real and imaginary power respectively). If you screw up and don't adjust properly to the instantaneous power flows (required battery charging current and/or load), then net power flows into or out of the DC bus, causing the bus capacitors to be charged or discharged respectively. They are biggish capacitors, but even so with several amps of current for each kilowatt of power, the bus voltage will rapidly go too high or too low. So the DSP is constantly battling to keep the DC bus voltage within reasonable bounds. Plus, when the DC-DC converter is running, you effectively have the battery voltage transformed across the DC bus. When this is the case, things are a bit easier, but any errors will result in wrong values of battery charge or discharge current. It's pretty nifty what it all does. It's done by careful adjustment of the inverter's phase relative to the grid. Amplitude is adjusted to make the grid load close to unity. And this adjustment is made thousands of times per second. i will sure brush up my ac theory to understand this ...i hope also if you prodivde a picture so that i can follow up with your complicated yet precise explanation -------------------------------- so the very brief of your explanations is that once 2 sourse shift in phase by 1 degree with an L BETWEEN THEM "there will be voltage , small one across the L AND since current always is not in phase with voltage and have 90 degree of defrence that current how ever is actually in phase with the voltage of one of the 2 sources " AND thus power can flow form that source once ac come in and the inverter synchronize its output with the coming input ac suppose the user choose that inverter provides ac output for loads we get an inverter that does provides electricty and charges the battery in the same time if the inverter wants to suck as in it changes phase a bit if its wants to spits its own ac it also changes the phase a bit in tiny seconds the same igbts that were rectify ac to create dc they may switch the dc high bus across the transformer and create low voltage ac for themosfets to rectify it and create the dc charging for battery wow wow amazing >>>have i got it mr colomb pleae tell me if what my ideas in mind are right thanks ------------------------------- Edited August 23, 20232 yr by wael_fathe
August 24, 20232 yr 7 hours ago, wael_fathe said: Have I got it Mr Colomb Yes, pretty much. With utility charging, there are actually three full bridges (H arrangements of effectively 4 switching devices). Each of these is capable of bidirectional power flow. However, two of them (either side of the transformer) are not phase controlled; they are "dumb" bridges that adjust power flow so as to maintain the same voltage ratio. All the switches (transistors) in the DC-DC converter are driven with a fixed waveform: almost a square wave, with a small gap where neither the upper or lower switches (transistors) are turned on. So by adjusting the phase between the inverter output and the mains, power flows either mains to DC bus or the other way around. To charge the battery, the firmware arranges for power to flow from the mains to the DC bus. The higher DC bus voltage causes power to flow through the other two H bridges into the battery. Maybe you're ready now for the final piece of the design: the buck converter. What happens if the mains voltage is high and the battery voltage is low? It will charge the battery, yes, but way too fast! The inverter can easily push the 48 V battery up to well over 60 V, which is no good for the battery. So to match the voltages without wasting a lot of power, there is the buck converter. This allows for some tens of volts to exist across the buck converter without wasting much power, and so by varying the pulse width of the buck converter's switch/transistor, you get to regulate battery charging current. The firmware has a lot of work to do. It has to get all these pulse widths just right, making sure that the bus voltage doesn't get out of hand, that the AC output voltage, frequency, and phase are just right, that the maximum total and utility charge current limits are not exceeded, monitoring temperatures and controlling fans, and much more. Then there is all the co-ordination of paralleled and/or 3-phase machines for some models. And handling over a hundred different commands, and updating the display (though in many models that's a separate processor now). Edited August 24, 20232 yr by Coulomb
August 27, 20232 yr Author Stopping the journey for a short while to watch these two Aussies popping a 5000A fuse, and in doing so had to generate 20kA 😁😁crazy
September 2, 20232 yr Author On 2023/08/13 at 4:26 PM, BritishRacingGreen said: a Short Guide to Bring Up a 5kW Axpert Main Board in the Softest Possible Manner : Chapter 2 I think I have discovered the failure mode of Axpert inverters giving F03 , F06 and other measurement related errors at random times. Especially those that displays exactly 120V for the battery voltage . In chapter 1 I have brought up a 5kW main board without the need of supplying anything on the battery terminals. This is our objective so we can investigate the system power supplies , mosfet and igbt drivers without the power chain being powered at all. I have discovered lately that there are a number of inverters that works otherwise , but would display error F03 (battery voltage too high) . I had one incoming in an earlier post where I discovered the F03 being affected exactly when the -12V supply rail is either very low or missing. I could actually simulate the condition by removing the -12V at will , and observe the error with 120V battery being displayed. It struck me this morning while discussing the problem with a friend in Cape Town that has the same problem driving him crazy, that this -12V rail could be suffering the same dried-out capacitors as we are by now aware of the affect that have on the 5V and +12V rails. Typically when these capacitors run dry , the 5V is mostly affected and that we see by the lcd display powering up and shutting down cyclically. When I repair these machines by replacing the capacitors , I also replace the -12V filter capacitor as a rule of thumb. However its possible that the -12V capacitor can run critically dry before the 5V one does. But the symptoms are now a bit complicated . The machine still works but the -12V will fail at random instances , causing errors like F03 and F06 . The friend in Cape Town also experiences F06 at times. So I revisited the 5kW main board I have with the faulty -12V rail , removed the filter capacitor , and tested the capacitance for starters . It is horrifically bad . not even 1uF for a 100uF rating. Below is my schematic of the MAX7.2 SMPS , but please note that the 5kW one is similar . I have highlighted the filtering capacitors as shown . For 5kW there is only one capacitor per rail. and C116 for 5kW is 100uF instead of the 470uF shown. So when you power up the main board as per my procedure , you are probably going to see a nice 5V,12V and -12V on your multi-meter. There is only a very small load so the 100nF in parallel with the electrolytic , e.g. C117, is sufficient to smooth the input. So you will have to clip on about a 12R 10W resistor on the -12V load output to draw at least a 1A current , then check the output voltage. Ideally an oscilloscope on the C116 should be used to check the ripple as well. My friend in Cape Town is going to open up his machine and replace C116 with a new one , and give us feedback as well. But I am very optimistic that this is the root cause of the inadvertent errors. EDIT : The reason why the -12V supply rail is affecting measurements of the DSP is due to the fact that this supply , along with others , is used to power/bias the instrumentation op amps on the the controller card. Also , when you test a main board that has a couple of years service , replace the filter capacitors as shown on the schematic with new ones as a rule of thumb . EDIT 2 : A couple of weeks ago I repaired a machine for a member that had the lcd power cycling problem , but he also experienced the F03 problem at times when the LCD (5V) decided to work for long periods. The machine had the classic problem of the 5V and 12V filter capacitors that ran nearly dried. But I have not only replaced them , but others as well , including C116. So I have 'inadvertently' also cleared the F03 120V battery voltage problem. Which explains why he now does not get measurement errors any more. Edit 3 : To summarize : It is unreal how super important the accuracy , performance and stability of your SMPS system supply rails are . It can also lead to expensive failures like mosfet and igbt destruction , I have first hand experience of that in my short little journey. a Short Guide to Bring Up a 5kW Axpert Main Board in the Softest Possible Manner : Chapter 3 Part 1 ---- Testing the DC-DC converter ---- So at this stage we have powered the main board rail supplies via an external PSU feed , without any supply on the battery terminals , and we have no DSP controller card inserted. This is ideal in order to test all the various driver signals without having any power on the mosfets and igbts. Of course it is essential that you test both the battery bus and the high voltage bus for a short circuit. if there are short circuits it is most probably due to a failed igbt or mosfet. You will have to unsolder those devices that causes the short. Below you will find a block diagram of the dc-dc converter : This diagram will help you to understand the working of the dc-dc converter. It is a bidirectional converter and power may flow from either BAT to BUS or vice versa. When the inverter is in battery mode , the power flows from the BAT to the BUS . When the grid or pv is charging the battery , power flows from BUS to BAT . On either side of the high frequency transformer TX1 there is two full bridges, on the BAT side low voltage mosfets are used , and on the BUS side high voltage igbt's are used. Both full bridges are controlled by a two phase PWM controller of type 3525. In our case the 3525 does not vary PWM and therefore the duty cycle is fixed at about 50%. The frequency is about 38khz. The phase A and phase B is 180 degrees out of phase . The output signals can be enabled or disabled by the DSP via the shutdown control pin as shown. So your first question might be : how does the DSP control the direction of power flow . The answer is it does not have to. The answer lies in theory of supply and demand. When there is 50V battery voltage and 0V bus voltage , then power will automatically flow from left to right. The left hand side full bridge will chop the battery dc to ac thru TX1 and the ac produced on the right hand side of TX1 will be full wave rectified by the igbt full bridge. Notice that the transformer ratio of TX1 is 1:8 , meaning the BUS will be about 8 x that of BAT voltage , this will relate to 50V:400V , make sense doesn't it . 400V is what we need on the bus for the DC-AC converter. If the ratio between BAT and BUS are balanced ,Vbus = 8 x Vbat, then no power will flow anymore. If there exists an alternative BUS source , e.g. pv or grid , and Vbat goes lower than Vbus/8 , then guess what , power now flow from right to left. The igbt's now chop dc to ac for TX1 , and the mosfets on the battery side are now merely full wave rectifier. When I started to play with this in practice , I realized this is some kind of magic ! So this is my methodology for bringing up a DC-DC converter that had experienced a catastrophic failure. We going to first debug the driver circuits in a complete zone of comfort , no supplies on the BAT or BUS. Then we going to replace faulty mosfets and igbts. And lastly we are going to manually enable the 3525 PWM , supply a very low BAT supply of 3V (yes 3 volts!) and measure to see if we get 3x8 = 24V on the BUS side. Conversely , we going to inject 24V on the BUS side and check wether we get 3V on the BAT terminals ! . The promise is that we can now test the switching levels not only on the gates , but also between source and drain of the mosfets , and between emitter and collectors of the IGBT's . And if we getting satisfied , we up the 3V to 6V to 9v to 12V and so forth. This is all about bringing up failed sections in the softest possible manner . So in Part 2 I will provide details on how to bring of the drivers for phases A and B , and how to stimulate the 3525 PWN controller to deliver the sources of the driver signals. Also we will monitor the voltage ranges of the gate drivers as not to exceed maximum values. I will provide nice schematics of the drivers in order to help you with the debugging. In Part 3 we will power the chain as mentioned , and test the switching actions of the power devices. So watch out for Part 2 of this chapter 3. NOTE : as explained, the dc-dc converter is merely a simple open loop converter . It is not a voltage or current regulator . The rule of engagement is simple , if the BAT voltage is ratio-metrically higher than that of the BUS , power flows from BAT to BUS. If the BUS voltage is ratio-metrically higher than that of BAT , power flows from BUS to BAT. The ratio of TX1 is fixed at very close to 1:8 . So how do we control battery charge voltage and current? This is done upstream in the BUS circuit by a simple BUCK converter. Therefore the BUCK converter can control the BUS voltage on the left hand side of the bus , thereby regulating the final battery voltage and current. Edited September 3, 20232 yr by BritishRacingGreen
September 3, 20232 yr Great explanation and diagram. Just a couple of nits. In the below, I think you meant to show -12 V rather than +12 V (4 places): The other thing is that while the early models had a 1:8 transformer turns ratio. most of the later models (all with the 64 V "feature") have a 1:7 ratio. That's so that with a battery voltage of 64 V, the bus voltage is 448 V rather than 512 V, when the bus capacitors are rated at 500 V.
September 3, 20232 yr Author 6 hours ago, Coulomb said: Great explanation and diagram. Just a couple of nits. In the below, I think you meant to show -12 V rather than +12 V (4 places): The other thing is that while the early models had a 1:8 transformer turns ratio. most of the later models (all with the 64 V "feature") have a 1:7 ratio. That's so that with a battery voltage of 64 V, the bus voltage is 448 V rather than 512 V, when the bus capacitors are rated at 500 V. Thank you , I revised the diagram above (ver 1xB). As far as the tx ratio is concerned , my own measurements were consistent with a ratio of very near to 1:8 . However I need to qualify that I have not covered the whole dynamic range of voltages , I stayed below 120V on the BUS side. Also my converter was never under any form of load, so dc measurement always reflect the peak voltages on the filter capacitors.
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