2 hours ago, BritishRacingGreen said:

My statement on an earlier post in this thread  that its not really needed to preempt an upgrade turned out to be a liitle bit on the wild side. When you come to think of it, the slow unstable sawtooth-like 5V  supply to the DSP can only cause trouble eg. with non-volatile memory devices etc.  

Whats more the 12v rail 1000uF cap actually degrades more ungracefully, but the 12v loads are slightly more forgiving to dips as the DSP. 

So yes, I agree, Axperts older than  5 yrs should be upgraded. 

 

 

 

@Coulomb, the communication module of the  older MKS models is a small board with RS232 and USB interfaces.  The USB interface is centred around a Cypress native USB  controller or small SOC. I think the latter, because the chip has a firmware label on it, and the USB is HID, yet the output is standard serial which I think is just wired-OR with RS232 driver.Which implies Voltronics had to write a driver for it.

So it would appear if this chip is faulty, that it is not possible to replace it with a stock Cypress  item,. The chip type is near impossible to read from the conformal coated device  even with magnification. 

I actually have a module that has a faulty USB chip. My take on boards like these is just to buy a new one, but the old Axperts spare part are becoming like hens teeth. 

 

Edited May 20, 20233 yr by BritishRacingGreen

Hi BRG

I read quite a bit on your threads on this forum. Just maybe you can be of assistance?

I have a Mecer SOL-I-AX-5NB 5kW inverter which i just installed and was working perfectly with all the correct configurations. However, when i tested the solar input PV the test lead on the multimeter touched the chassis and i did notice a very small spark but no smoke or heat. The inverter error is the terrible 09. 

Is there any way that you an assist me to repair the diodes or the Mosfets to get this brand new inverter to life again?

If you can be of assistance i will really appreciate since repair companies are very difficult to find in SA

My e mail is: [email protected]

WhattsApp 072 213 1811 

If it cost effective to repair i will certainly value your input or advice

Best regards

J Nortje

25 minutes ago, J. Nortje said:

Hi BRG

I read quite a bit on your threads on this forum. Just maybe you can be of assistance?

I have a Mecer SOL-I-AX-5NB 5kW inverter which i just installed and was working perfectly with all the correct configurations. However, when i tested the solar input PV the test lead on the multimeter touched the chassis and i did notice a very small spark but no smoke or heat. The inverter error is the terrible 09. 

Is there any way that you an assist me to repair the diodes or the Mosfets to get this brand new inverter to life again?

If you can be of assistance i will really appreciate since repair companies are very difficult to find in SA

My e mail is: [email protected]

WhattsApp 072 213 1811 

If it cost effective to repair i will certainly value your input or advice

Best regards

J Nortje

Hi @J. Nortje, ag man, thats no good news.  The shorting of pv inputs to earth, even momentarily, will blow the igbt's of the DC-AC inverter, and in some cases the DC-DC converter's igbt's as well. With real bad luck the PCB might also be damaged. But this is worst case.

But not all is doom and gloom. If the PCB is servicable, we can get your get your machine serviceable again. 

PM me and provide me your location. 

Hi BRG

Thank you for your rapid response to my issue with the  faulty 5kW Mecer inverter. 

My location is Witbank (Mpumalanga) if there is some way of assisting me

I presently have three of the same Mecers running in parallel with no problems at all for at least the last two years with ICC and Solar assistant for monitoring and control on three sets of 200AHr  AGM's

Presently in process of switching to Pylontec US 3000C's  

The faulty Mecer is still boxed and as mentioned brand new

Is there any other way that i may PM you as i am not always on the Power forum?

Thank you for your welcome assistance

Regards

1 minute ago, J. Nortje said:

Hi BRG

Thank you for your rapid response to my issue with the  faulty 5kW Mecer inverter. 

My location is Witbank (Mpumalanga) if there is some way of assisting me

I presently have three of the same Mecers running in parallel with no problems at all for at least the last two years with ICC and Solar assistant for monitoring and control on three sets of 200AHr  AGM's

Presently in process of switching to Pylontec US 3000C's  

The faulty Mecer is still boxed and as mentioned brand new

Is there any other way that i may PM you as i am not always on the Power forum?

Thank you for your welcome assistance

Regards

Ok, I just noticed your post has phone no. I will Whatsapp you took tommorrow. 

On 2023/02/11 at 7:39 AM, BritishRacingGreen said:

Hi @Coulomb I had been invited to visit a home owner's site who had a nasty failure on one of two Kodak OG-PLUS 5.48 (King)  inverters that operated in parralel.  Each inverter is fed with 8x550W panels. Central battery consists of 3xPylontech US3000 packs.  The battery wouldnt allow output, even though the onoff switch and reset button responded without raising alarms. The green led kept flashing which means BMS is up.

I took the faulty King home and opened up. Fed 50v PSU as to produce battery discharge power. Started up perfectly and produced 220vac in battery mode. Added grid input and set option to grid charge, charger output raised to preset value. So the main board and control board functionality seems ok. 

Removed MPPT module, one row of mosfets damaged severely. Closer inspection reveals no explosion evidence, the damage was caused by severe over heating (over current?) 

So it appears that something went wrong on PV side, which caused either a short or over voltage on battery bus, which caused to Pylons to go in deep protection, although the pylons not raising an alarm. 

No damage on second King. 

What are the typical failure modes of these MPPTs, i see they low voltage and feeds the battery bus, as oppose to the HV dc bus. 

The site system design i unvestigated and found no flaws, except the panels which is 4400 W, and the King max MPPT rating is 4000W.  Pv voltage is 90VDC, so it suggest 2S4P panel config. So voltage and current specs well within MPPT limits, but power not.  EDIT: as far as power is concern, am i correct by assuming that the MPPT controller / main DSP should limit pv output accordingly when the power is exceeded above its spec.? 

The failure occured on bright sunny day, clears skies, hot. 

 

EDIT:  due to the Pylons closing shop, the owner has tempirary wired in 4 big lead acids, and the second inverter is carrying the system. 

EDIT: if there is any member that could shine some light on the Pylon failure mode, i would appreciate. I have learned there is app called BatteryView I can connect to RS233 console, hopefully this will reveal some status. 

the pylontech is 0.5c charge so if both inverters were pushing max amps the 183amps would exceed the 150A you can push into 3 batteries and naturally  if one is full before the others due to cable lengths differences even more so

ie lets say you aren't pushing more than the 150a so lets say you charge 110a combined and the one battery is full it stops taking charge as bms disconnects cell from the charge , now the 110a is divided over 2 exceeding their charge limit 

 

protection mode can be hit, if the charging was on full tilt

18 minutes ago, Leondavibe said:

the pylontech is 0.5c charge so if both inverters were pushing max amps the 183amps would exceed the 150A you can push into 3 batteries and naturally  if one is full before the others due to cable lengths differences even more so

ie lets say you aren't pushing more than the 150a so lets say you charge 110a combined and the one battery is full it stops taking charge as bms disconnects cell from the charge , now the 110a is divided over 2 exceeding their charge limit 

 

protection mode can be hit, if the charging was on full tilt

The US3000 pylons went into protection  due  overvoltage that came from the faulty MPPT. 

This was evident in the logs, and also evident by the  bms failure that I repaired. 

Yesterday I nearly decided to stop my journey , pack my solar suitcase, delete my forum account, and walk off in the sunset.

I have done so much homework in order to leave very little if any to the imagination regarding the repair of faulty IGBT bridges. And yesterday I started with great confidence on a machine that was destroyed due to inadvertant grounding of a PV terminal.

So I removed the 4 DC-AC converter's IGBTs and heatsink. Then switch on and check the drivers on DSO. All four looked pretty good, voltage levels -5.4 for turnoff and 15v for turning. Waveform shapes pretty good to my own basis of comparison.

Ok next I temporary solder test igbts onto the board  ,in two test phases  of half bridge only as I have described earlier in this topic. Passed, then I solder all 4 in full bridge mode . Switch on . 220vac beautifully. Doesn't get easier than this.

Then I left it running for a while , and because the igbts are not heatsinked, I touch the plastic case with my bear hands to gauge temperature.BOOM !  the abrupt  explosive sound so  heavy that I was completely deaf for a couple of seconds , then partial deafness for a good two hours after the bang.

I was devastated to say the least , this is not on , and somewhere my procedure have exposed to be flawed. I investigated the circuit and found the gate pin of the IGBT that I touch to be loose , dry joint.!!!!

HA HA , I felt better. Here is the thing .once a gate pin is left hanging , guess what ,the valves meet the pistons, timing belt broken.  The high impedance of the gate will  create indeterministic switching.

LESSON 1 when you do temp rigging , check the quality of your connections/joints.

So no I remove the 2 faulty igbts (it's mate in the same bridge leg will also get destroyed. Turn on and check waveform again.passed.

Solder 2 new test igbts in and this time used about 100 grams of solder to secure connections. Switch on .BOOM.BOOM.  now you can understand my opening statement.

I have now lost faith.  But our fathers have not raised scared children , reckless yes, but not scared. This time around there was no dry joints. I removed the 2 faulty IGBTs again , and tested the driver waveforms again and again and again.ha ha .one driver had a shaky -5 volt trace , what's more the waveform edges not so good anymore. Start tracing the driver.now the gate series resistor is 47R . But it measures around 30k.Shit , so the igbt went faulty due to the first BOOM  and blew this resistor   . But not open circuit , enough resistance to fool the DSO, but this resulted in very bad switching performance if the new IGBT that went during BOOM 2. So basically the we cannot switch the IGBT on abruptly and we cannot switch it off in good time.And that's what caused the BOOM 2. 

LESSON 2: please check this resistor even though your driver waveforms looks ok.

There was no BOOM3.  I feel better now.lots of lessons learned.

Sounds like you had some fun 🤣🤣🤣🤣 & had to change your underpants at least once. 

Don't leave us no matter what the outcome. In fact often most learning takes place from failure. We often learn nothing from successes, because the analysis of success is not as much as a failure. When you connect something & it just works you walk away & have a beer. In an "event" we analyse what we know or don't know yet & scratch Deep into our knowledge pockets. 

1 hour ago, BritishRacingGreen said:

Yesterday I nearly decided to stop my journey , pack my solar suitcase, delete my forum account, and walk off in the sunset.

I have done so much homework in order to leave very little if any to the imagination regarding the repair of faulty IGBT bridges. And yesterday I started with great confidence on a machine that was destroyed due to inadvertant grounding of a PV terminal.

So I removed the 4 DC-AC converter's IGBTs and heatsink. Then switch on and check the drivers on DSO. All four looked pretty good, voltage levels -5.4 for turnoff and 15v for turning. Waveform shapes pretty good to my own basis of comparison.

Ok next I temporary solder test igbts onto the board  ,in two test phases  of half bridge only as I have described earlier in this topic. Passed, then I solder all 4 in full bridge mode . Switch on . 220vac beautifully. Doesn't get easier than this.

Then I left it running for a while , and because the igbts are not heatsinked, I touch the plastic case with my bear hands to gauge temperature.BOOM !  the abrupt  explosive sound so  heavy that I was completely deaf for a couple of seconds , then partial deafness for a good two hours after the bang.

I was devastated to say the least , this is not on , and somewhere my procedure have exposed to be flawed. I investigated the circuit and found the gate pin of the IGBT that I touch to be loose , dry joint.!!!!

HA HA , I felt better. Here is the thing .once a gate pin is left hanging , guess what ,the valves meet the pistons, timing belt broken.  The high impedance of the gate will  create indeterministic switching.

LESSON 1 when you do temp rigging , check the quality of your connections/joints.

So no I remove the 2 faulty igbts (it's mate in the same bridge leg will also get destroyed. Turn on and check waveform again.passed.

Solder 2 new test igbts in and this time used about 100 grams of solder to secure connections. Switch on .BOOM.BOOM.  now you can understand my opening statement.

I have now lost faith.  But our fathers have not raised scared children , reckless yes, but not scared. This time around there was no dry joints. I removed the 2 faulty IGBTs again , and tested the driver waveforms again and again and again.ha ha .one driver had a shaky -5 volt trace , what's more the waveform edges not so good anymore. Start tracing the driver.now the gate series resistor is 47R . But it measures around 30k.Shit , so the igbt went faulty due to the first BOOM  and blew this resistor   . But not open circuit , enough resistance to fool the DSO, but this resulted in very bad switching performance if the new IGBT that went during BOOM 2. So basically the we cannot switch the IGBT on abruptly and we cannot switch it off in good time.And that's what caused the BOOM 2. 

LESSON 2: please check this resistor even though your driver waveforms looks ok.

There was no BOOM3.  I feel better now.lots of lessons learned.

When I went to bed , I revisited all my procedures , and came to the conclusion that the ideal test bed for the IGBT full bridge will be to remove the large HV capacitors and replace with a small electrolytic, just enough to smooth the bus , but low on energy. It's no use using a current limited power supply on the battery end.bottom line is these big caps accumulate a lot of charge.

Then the remove the controller card, and use a test controller to pump the bus soft start  to something like 80 volts pressure. Maintain this voltage by reading back the bus voltage into the test controller.

Then generate the 4 timing pulse trains for the igbts with the test controller.its not that difficult . The PWM can be rough to generate a reasonable sine wave. If all goes well, ramp up the soft start to ultimately 310v.

I have actually started with this morning , and going to use it on @ChristoSnake Infini , which I am busy debugging.

Edited May 27, 20233 yr by BritishRacingGreen

7 minutes ago, Steve87 said:

Sounds like you had some fun 🤣🤣🤣🤣 & had to change your underpants at least once. 

Yep , there were skid marks in it,😎

Edited May 27, 20233 yr by BritishRacingGreen

On 2023/05/27 at 10:47 AM, BritishRacingGreen said:

Yesterday I nearly decided to stop my journey , pack my solar suitcase, delete my forum account, and walk off in the sunset.

I have done so much homework in order to leave very little if any to the imagination regarding the repair of faulty IGBT bridges. And yesterday I started with great confidence on a machine that was destroyed due to inadvertant grounding of a PV terminal.

So I removed the 4 DC-AC converter's IGBTs and heatsink. Then switch on and check the drivers on DSO. All four looked pretty good, voltage levels -5.4 for turnoff and 15v for turning. Waveform shapes pretty good to my own basis of comparison.

Ok next I temporary solder test igbts onto the board  ,in two test phases  of half bridge only as I have described earlier in this topic. Passed, then I solder all 4 in full bridge mode . Switch on . 220vac beautifully. Doesn't get easier than this.

Then I left it running for a while , and because the igbts are not heatsinked, I touch the plastic case with my bear hands to gauge temperature.BOOM !  the abrupt  explosive sound so  heavy that I was completely deaf for a couple of seconds , then partial deafness for a good two hours after the bang.

I was devastated to say the least , this is not on , and somewhere my procedure have exposed to be flawed. I investigated the circuit and found the gate pin of the IGBT that I touch to be loose , dry joint.!!!!

HA HA , I felt better. Here is the thing .once a gate pin is left hanging , guess what ,the valves meet the pistons, timing belt broken.  The high impedance of the gate will  create indeterministic switching.

LESSON 1 when you do temp rigging , check the quality of your connections/joints.

So no I remove the 2 faulty igbts (it's mate in the same bridge leg will also get destroyed. Turn on and check waveform again.passed.

Solder 2 new test igbts in and this time used about 100 grams of solder to secure connections. Switch on .BOOM.BOOM.  now you can understand my opening statement.

I have now lost faith.  But our fathers have not raised scared children , reckless yes, but not scared. This time around there was no dry joints. I removed the 2 faulty IGBTs again , and tested the driver waveforms again and again and again.ha ha .one driver had a shaky -5 volt trace , what's more the waveform edges not so good anymore. Start tracing the driver.now the gate series resistor is 47R . But it measures around 30k.Shit , so the igbt went faulty due to the first BOOM  and blew this resistor   . But not open circuit , enough resistance to fool the DSO, but this resulted in very bad switching performance if the new IGBT that went during BOOM 2. So basically the we cannot switch the IGBT on abruptly and we cannot switch it off in good time.And that's what caused the BOOM 2. 

LESSON 2: please check this resistor even though your driver waveforms looks ok.

There was no BOOM3.  I feel better now.lots of lessons learned.

The machine is doing very well with its new DC-AC converter . But today I added grid input to check grid charging  for battery. The charging voltage ran at 66vdc , no good. The only problem I could think of was the buck IGBT or its driver. The high side IGBTs of the DC-DC converter cannot be at fault  because they only chop to produce AC for HV transformer to the battery.they don't regulate , the buck regulates. 

So I opened the machine and found 6.8 ohm between collector and emitter of the buck IGBT. Cut the emitter leg and the transistor is shorted to 6.8 ohm. I still don't know how I missed it before, maybe I was too occupied with the DC-AC converter failures.EDIT : I think I know why the buck failed , because I am sure I initially tested it as good. The thing is the IGBT drivers of the 2 low side bridge igbts and the buck IGBT share the same isolated power supply,because their emitters are all referenced to same point (bus-). So the chances are always there that the buck may also fail during the failures of the full bridge.

The 66vdc now make sense, the buck is just a passthru and the battery will be at the maximum open loop voltage that the DC bus can produce. By the way error 03 comes on.

Replaced the IGBT after checking the driver circuit , and fixed ! Regulated battery charge voltage as per settings 26 and 27.

Edited May 28, 20233 yr by BritishRacingGreen

Just want to share the basic bus topology of  @ChristoSnake  ' 5kW Infini grid-tier . Below is a very  simple schematic of the low voltage battery bus and the high voltage bus , showing the DC-DC converter and buck circuits , but not the DC-AC converter. What I want to point out is the split supply HV DC bus that I have previously mentioned.

1. On the left hand side is the low 48V battery dc bus . Noteworthy is the fact that there are 2 x 2.5kW  sections. I  initially thought this was just dual effort to split power , but no , its dual in order provide a split high voltage dc bus .What's nice on the infini is that this module is a separate board , and on it the supplies are generated isolated , i.e. complete independent. Only on the main board are the two N terminals joined , as to effectively form a positive bus wrt to neutral , and a negative bus wrt to neutral . 

2. So what's the deal with split supply ?  . For a single ac output , nothing , because the ac live and neutral can be  performed via full bridge DC-AC converter from a single bus supply. But the moment you go multiphase , 2ph or 3ph, you cant go full bridge because guess what , your neutrals cannot be tied together  from the individual full bridges. So there are 2 options , you either use a split dc supply and then use a half bridge centered around a hard fixed neutral as shown above . Option 2 is you use a delta to Y conversion transformer , which for my untrained eye seems to be expensive , but some of the large three phase machine like the ATESS 100kw use this isolation transformer to create a hard neutral for unbalanced loads . I guess the isolation  feature becomes important !? 

3. The buck circuit is not your average Axpert circuit , instead there is an igbt instead of diode . This makes me think that this might be  a buck-boost configuration , not only buck . @Coulomb would you agree ?

Although @ChristoSnake 5kW machine is 5kW singe phase , it has been designed for a 2ph split ac supply  . The main board merely combines to two supplies , so internally this machine is really two  2.5kW inverters in parallel !!!

Christo's machine suffers from a short on the battery bus due to some mosfets shorted. I have already isolated them . The beautiful thing is the both the mosfet and igbt drivers are pretty much stock standard as we are use to on the Axperts.  mosfets and bridge igbt's are built around the standard 3525 PWM chip with isolation transformers , so its actually very easy to stimulate them with a 12V and -12V supply . The buck igbts is not so easy . The buck igbts are controlled from the dsp , which I can simulate with my pi pico controller , but the isolation transformer is driven from the SPS main feed which is the damped oscillating output  from the SPS flyback transformer. That is my next challenge , I cannot generate that waveform , but I could probably inject a 9-15 volt ac transformer output in order to equal the energy magnitude and 20V ac peak requirement.

 

 

Edited May 31, 20233 yr by BritishRacingGreen

Hi @Coulomb , I have noticed on the older MKS Axpert machines that the low voltage MPPT's are not as stable as far far as regulation is concerned on the battery output.  This is in contrast to grid charger via the buck converter. Admittedly , I did not connect a battery to the terminal , instead a regulated power supply with a blocking diode.  So one wonders if the design is dependent on a battery , which will provide for additional filtering .  The MPPT does regulate , but at times drift from the nominal charge voltage up to  250-300mV either direction.

Further to this , I have connected a 300W load (stove plate !) on the battery terminals . Under these conditions  the MPPT is much more stable . But when you remove the 300W battery load , the voltage shoots up to 57V (from 53.5V) momentarily (1 second) and then stabilize . 

 

Edited May 31, 20233 yr by BritishRacingGreen

14 hours ago, BritishRacingGreen said:

3. The buck circuit is not your average Axpert circuit , instead there is an igbt instead of diode . This makes me think that this might be  a buck-boost configuration , not only buck . @Coulomb would you agree ?

Cautiously, yes. Perhaps boosting the bus voltage allows for clip-free operation with lower voltage batteries, while allowing the use of higher voltage batteries as well. In other words, overcoming the limitations of the 64 V models.

13 hours ago, BritishRacingGreen said:

Admittedly , I did not connect a battery to the terminal , instead a regulated power supply with a blocking diode.  So one wonders if the design is dependent on a battery , which will provide for additional filtering.

I'd say that the MPPT control code is expecting a battery, and will have gains tuned to having a battery there. Hence the extra stability with the stove element across the "battery" power supply.

I'm actually surprised that the utility charger works so well without a real battery there.

I have the same problem (flashing LEDs).  Unfortunately, I am not technically minded and would not try to repair myself if necessary.

We are on a farm in the Karoo.  Over the last 6 months or so this happens if there is a "power-down" for some reason.  Say failing batteries.  In the past, it would take a day or so before the batteries would fully charge and then mysteriously with on-and-off switching it would start working again.

We recently replaced the gel batteries with a Li unit.  Same flashing LEDs until the unit was fully charged.  Then it still took 4 - 6 hours before I got it operational again.

Three weeks later and the unit was making a strange light grinding sound.  I powered down and then on again - the fast flashing problem was back and persisted for 3 hours yesterday.  I powered up this morning and 4 hours later still no joy.

Any help will be most appreciated.

2 hours ago, PVA said:

I have the same problem (flashing LEDs).  Unfortunately, I am not technically minded and would not try to repair myself if necessary.

We are on a farm in the Karoo.  Over the last 6 months or so this happens if there is a "power-down" for some reason.  Say failing batteries.  In the past, it would take a day or so before the batteries would fully charge and then mysteriously with on-and-off switching it would start working again.

We recently replaced the gel batteries with a Li unit.  Same flashing LEDs until the unit was fully charged.  Then it still took 4 - 6 hours before I got it operational again.

Three weeks later and the unit was making a strange light grinding sound.  I powered down and then on again - the fast flashing problem was back and persisted for 3 hours yesterday.  I powered up this morning and 4 hours later still no joy.

Any help will be most appreciated.

Hi @PVA, sorry to hear about your machine, please send me an image of your front of inverter, as well as a image of label on the side.

Are the symptoms the same as the video clip earlier in this thread? 

Near what town are you located, eg Beaufort, Leeu Gamka, Victoria West, Hutchinson, Laingsburg ( I know people in these locations) or are you in the Klein Karoo? 

Also can you find out what your courier cost will be to Cape Town  or Johannesburg.?  I had someone in Goodwood that paid under R200 to me in  Jhb one way. 

 

 

Edited June 12, 20232 yr by BritishRacingGreen

5 hours ago, PVA said:

the fast flashing problem was back and persisted for 3 hours yesterday.

I know it's highly inconvenient (possibly the understatement of the day), but it's not good for the inverter to leave it running in that condition. I accidentally left mine twitching like that for about 12 hours, and it (presumably) caused a fault on the control board that stopped solar charging. Well, the fault appeared right after that twitching. I eventually fixed the solar problem, but now I'm getting fault codes and it won't run the inverter proper, now with fault code 09 (fortunately not due to the usual cause, i.e. shorted DC bus). My working theory is that some capacitors on the control board were marginal, and this twitching tipped some of them over the edge. Replacing one capacitor changed the fault code, suggesting to me that capacitors are possibly the problem.

On 2023/05/31 at 7:50 PM, BritishRacingGreen said:

Just want to share the basic bus topology of  @ChristoSnake  ' 5kW Infini grid-tier . Below is a very  simple schematic of the low voltage battery bus and the high voltage bus , showing the DC-DC converter and buck circuits , but not the DC-AC converter. What I want to point out is the split supply HV DC bus that I have previously mentioned.

1. On the left hand side is the low 48V battery dc bus . Noteworthy is the fact that there are 2 x 2.5kW  sections. I  initially thought this was just dual effort to split power , but no , its dual in order provide a split high voltage dc bus .What's nice on the infini is that this module is a separate board , and on it the supplies are generated isolated , i.e. complete independent. Only on the main board are the two N terminals joined , as to effectively form a positive bus wrt to neutral , and a negative bus wrt to neutral . 

2. So what's the deal with split supply ?  . For a single ac output , nothing , because the ac live and neutral can be  performed via full bridge DC-AC converter from a single bus supply. But the moment you go multiphase , 2ph or 3ph, you cant go full bridge because guess what , your neutrals cannot be tied together  from the individual full bridges. So there are 2 options , you either use a split dc supply and then use a half bridge centered around a hard fixed neutral as shown above . Option 2 is you use a delta to Y conversion transformer , which for my untrained eye seems to be expensive , but some of the large three phase machine like the ATESS 100kw use this isolation transformer to create a hard neutral for unbalanced loads . I guess the isolation  feature becomes important !? 

3. The buck circuit is not your average Axpert circuit , instead there is an igbt instead of diode . This makes me think that this might be  a buck-boost configuration , not only buck . @Coulomb would you agree ?

Although @ChristoSnake 5kW machine is 5kW singe phase , it has been designed for a 2ph split ac supply  . The main board merely combines to two supplies , so internally this machine is really two  2.5kW inverters in parallel !!!

Christo's machine suffers from a short on the battery bus due to some mosfets shorted. I have already isolated them . The beautiful thing is the both the mosfet and igbt drivers are pretty much stock standard as we are use to on the Axperts.  mosfets and bridge igbt's are built around the standard 3525 PWM chip with isolation transformers , so its actually very easy to stimulate them with a 12V and -12V supply . The buck igbts is not so easy . The buck igbts are controlled from the dsp , which I can simulate with my pi pico controller , but the isolation transformer is driven from the SPS main feed which is the damped oscillating output  from the SPS flyback transformer. That is my next challenge , I cannot generate that waveform , but I could probably inject a 9-15 volt ac transformer output in order to equal the energy magnitude and 20V ac peak requirement.

 

 

its mid-winter here on the Highveld  , and if you can imagine how slow molasses move on a very cold winters morning , well that's me . But I have made a small advancement on @ChristoSnake infini . I have repaired the faulty mosfets/igbts on the battery board with temporary low current devices for testing purposes. Then excited the 3525 PWM circuits , and fed 5V on the battery bus . The switching waveforms on the semiconductors igbt's and mosfets number one. I am running out of power supplies though , you really need plenty of them. 

So with 5V on the battery terminals I got 34V on the dc bus , which suggest about a voltage transfer ratio of 6.6 factor , sounds about ok.

Next up I am going to test the reverse direction . from dc bus to battery . Then increase the voltages . so its pretty much scalable tests , I am very cautious with the infini in this regard.

33 minutes ago, BritishRacingGreen said:

its mid-winter here on the Highveld  , and if you can imagine how slow molasses move on a very cold winters morning , well that's me . But I have made a small advancement on @ChristoSnake infini . I have repaired the faulty mosfets/igbts on the battery board with temporary low current devices for testing purposes. Then excited the 3525 PWM circuits , and fed 5V on the battery bus . The switching waveforms on the semiconductors igbt's and mosfets number one. I am running out of power supplies though , you really need plenty of them. 

So with 5V on the battery terminals I got 34V on the dc bus , which suggest about a voltage transfer ratio of 6.6 factor , sounds about ok.

Next up I am going to test the reverse direction . from dc bus to battery . Then increase the voltages . so its pretty much scalable tests , I am very cautious with the infini in this regard.

On the need of additonal power supplies , I stumbled across a low cost 80v dc - dc converter which I am seriously considering as a bench supply for Machines-Under-Test .  But I had to laugh . 600W . No ways .  I will still buy the module , even for 150W derated . I  love the Chinese engineering specs : ' 

• Output Current: 12A Max (please increase heat dissipation when exceeding 10A)(The higher the voltage difference, the lowers the current)

'please' is not an sensible engineering term.😎

https://www.robotics.org.za/BOOST-600W-10A

 

Edited June 12, 20232 yr by BritishRacingGreen

2 hours ago, BritishRacingGreen said:

On the need of additonal power supplies , I stumbled across a low cost 80v dc - dc converter which I am seriously considering as a bench supply for Machines-Under-Test .  But I had to laugh . 600W . No ways .  I will still buy the module , even for 150W derated . I  love the Chinese engineering specs : ' 

• Output Current: 12A Max (please increase heat dissipation when exceeding 10A)(The higher the voltage difference, the lowers the current)

'please' is not an sensible engineering term.😎

https://www.robotics.org.za/BOOST-600W-10A

 

When LS started in 2008 I had the need to boost my car battery to 24V for a pure sine UPS. At that time I bought a cheap 150W boost converter. I had the same kind of spec. Use extra heat sink for cooling over 50W. 

I fitted a CPU fan on my input side and a MCB that would trip. And yes this boost converter is still working fine but it does have a low efficiency. Depending on current/voltage setting as low as 60%.

Hi @Coulomb I need to replace a cluster of  battery side Mosfets for the 5kW Infini I am working on . The required device is IRFP4468  . However , I can only lay my hands on the IRFP4668 . Below please find extract from the data sheets showing  the fundamental differences between the two (differences are not limited to what is being shown though):

 

 

 

The fundamental difference is the very low Rds of milli  2.6 ohm of the 4468  vs 9.7 milli ohm of the 4668. Also the current rating of 4468 is higher than that of 4668. The 4668  sports  a 200V Vds  as opposed to 100V , but that will not be important for me , as long as I match the 100V of 4468.

Voltronics use both in the Axperts / Infini . The 4668 is used in MAX 7.2 - 10 Kw . On the MAX  there are 3 x 4668 in parallel per switching element  to drive a 5kW section of DC-DC converter , there are two 5kW sections  for 7.2 - 10kw MAX. On the Infini 5kW there are two 2.5kW sections , each section has 2 x 4468 in parallel as a switching element.  The switching elements of both MAX and Infini  are configured to drive the same duty cycle of power , regardless whether they are in half or full bridge mode.

So on the MAX 10kW , a switching element of 3 x 4668 in parallel   is good for 5kW . So using these 4668's in the infini , would you say 2 x 4668 in parallel  is ok for a derated power of 2.5kW ?

The effective heat sink size  per device on the infini is smaller than that of the max , I  would say 75%.

So now we have 2 x 4668 in parallel which gives 9.76 / 2 = 4.84 m ohm. This is opoosed to 2 x 4468 in parralel which is 1.3 m ohm . Is this going to be a show stopper in terms of heat dissipation ?. I would on face value say yes , but then again the max 10kW configuration says otherwise. Your thoughts ?

For both 4468 and 4668 Voltronics use the same driver circuits , so I am confident as far as the rest of the DC and AC characteristics of the devices are concerned.

 

Edited June 15, 20232 yr by BritishRacingGreen

16 hours ago, BritishRacingGreen said:

would you say 2 x 4668 in parallel  is ok for a derated power of 2.5kW ?

 

So the 4668 has 4x the Rdson of the 4468, so that means half the current will yield the same dissipation (considering only resistive losses, switching losses is probably lower on the 4668).

P = I²R

20²*0.002 == 10²*0.008

So it should be able to do 2.5kW if you have some way to actually enforce that limit.