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BritishRacingGreen

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BritishRacingGreen last won the day on September 12

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    Germiston
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    Embedded hardware/software , Linux , ARM CPU , railway signaling and solar.

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  1. is this good enough for grounding ? Asking for a friend.
  2. I repaired my neighbour's Nemtek Wizzord recently. I have also noticed that the 12V battery had been run down to 0V. After repair of the low voltage board, I substituted the battery with a 12V bench psu and found when lowering this voltage that the unit 'cuts off' when voltage goes below 11V. This looks promising, except the microcontroller does not switch off and a current of 45mA is still being drawn. This of course depletes the battery over weeks or months, and destroys the battery. Please take note of this when energizer is unattended for long periods of time. Also the mains charging voltage is 14.0V. Isnt this a bit high for a continuous float charge?
  3. Dry Joints and Axpert Error 06 Good day, hardware hackers. It’s only human not to share all of our failures on a public forum, but this one I need to share with you. I recently repaired a 5kW Axpert that had the dreaded Error 09. While there are worse traumas in life than Error 09, it is indeed problematic. Invariably, you need to replace 40-60% of the power silicon (MOSFETs/IGBTs), and it’s almost guaranteed that some gate drivers are faulty as a result of the big bang. I repaired the machine following my methods to bring it up in a deterministic 'soft' manner, and the initial test/verification went very well. However, a few days after the repair, I used the same machine to test a Pylontech US3000, which had a fried BMS power chain. About half an hour later, the Axpert displayed Error 06. I reset the machine, and either Error 06 appeared immediately again, or it would fail after a random period of time, which could be as long as one hour. Error 06 indicates that the AC output voltage is too high. Since there was no Bus Voltage Too High error, I suspected that the DC-AC full bridge might be at fault. This wasn’t due to clever deduction; rather, I knew that this bridge had been severely zapped during Error 09, resulting in the replacement of some gate drivers and gate resistors. Even though the full bridge was not faulty most of the time, I suspected the quality of the gate drive performance. I decommissioned the machine and disassembled it. The first thing I typically do is test the 47Ω gate drive resistor path from driver output to the IGBT gate pin. Guess what? One of those four paths had high resistance. It was a dry joint or a faulty resistor. The annoying thing was that it wasn’t open circuit but had an unstable value between 300Ω and 150kΩ (!!!!). I tested the resistor, which was fine at 47.2Ω, but I noticed a terrible solder joint on one pad. I tell you, I tested this circuit for continuity during the Error 09 repair. Nonetheless, I repaired the joint and checked all four circuits again. I reassembled, tested, burned in for 24 hours, and the Error 06 was gone. So, why the Error 06? Here’s my theory: We know that the IGBT gate has parasitic capacitance, which influences the switching times due to the RC time constant, where R is the gate drive resistance. The smaller we make the gate resistance, the shorter the gate switch-on or switch-off times will be. This explains the typical gate resistor values of 22Ω - 47Ω. We also notice in typical gate driver schematics that the driver DC supplies, referenced to the IGBT emitter, are asymmetrical (+15V and -5V). This means that the turn-off delay is somewhat longer than the turn-on delay in practice, because the gate voltage must discharge from +15V down to about the gate threshold voltage of 2-3V. This takes longer than switching the gate on, which requires raising the gate voltage from -5V to about 2-3V. This difference becomes significant when the RC time constant is quite large. The net effect is that the intended PWM duty cycle, controlled by the DSP controller, becomes distorted at the gate of the IGBT. As a result, your duty cycle ON periods will be longer than intended. This, in turn, causes the integrated voltage on the collector of the IGBT to become increasingly higher, leading to the “output voltage too high” error. I also believe that this is one reason why some IGBTs with large gate capacitances require a resistor anti-parallel arrangement. An additional resistor is connected in parallel with the gate resistor, but via a steering diode. The polarity of the steering diode is chosen to lower the net gate resistance when the IGBT is switched off (gate discharged). So, how do we test all this in practice? The first option is to have a dual-channel oscilloscope, with one channel connected to the DSP control signal and the other connected to the IGBT gate. However, these two signals are not in the same power domain, so I don’t typically go this route. One could connect the grounds together via suitable high resistors, probably in the order of 500kΩ - 1MΩ, but I haven’t tried that yet. The second option is to use only one channel and monitor the voltage across the gate resistor. This waveform represents the current through the gate and provides a lot of information. An example waveform is shown in the oscillogram below: The actual gate turn-on occurs during the positive-going pulse. This current pulse results from charging the gate capacitor to the 15V voltage level. The gate turn-off occurs during the negative-going pulse, which relates to discharging the gate capacitor. In this waveform, the period between on and off is about 6µs, so in practice, you need a 40kHz square wave to produce this as a test. Neither the gate charge pulse nor the gate discharge pulse plays a significant role due to their short durations. What I do is remove the DSP controller and inject a square wave on the relevant control pin of about 40kHz. Then I check the current profile as shown above. Under circumstances where the gate resistance is out of spec, you will see quite wide charge and discharge pulses. Cheers, and happy hacking!
  4. Ok, then yes your total yield is a low in relation to 12 x 555W. You should be enjoying at least a good average of 4kw on peak if not more. What is the pv voltage when you drawing that odd 2kw from it.?
  5. You say you get 1.6kw charge but what is the total yield of the pv? Maybe your load priiority is SUB or SBU in which case load is priority, then charging. So maybe the pv is delivering more than 1.6kw but is routed to load.
  6. In order to stay safely away from the protection limits of the BMS, in the case where your rectifier is a dumb charger (no bms comms). Remember this : even without bms to charger communication, the bms can still perform its protection functions. A conservative charge voltage will not be able to get your pack to 100% SOC. But you have a use case where you dont need that. The hysteresis levels for triggering is typically 80% SOC generator off and say 40% SOC generator on.
  7. One drawback is that generator must have enough capacity to both charge a depleted battery as well as supplying the load demand. If not the rectifier must have suitable current limiting capability. In an ac coupled arrangement the inverter can be configured to impose a lower charge current limit when it is in generator mode.
  8. I dont have field experience here, but I can assure you one thing that the battery is now a perfect filter component as far as the generator is concerned. It does not get better than this. Your lithium battery has got such a low source impedance that it will just suck up any surge that the load wishes to impose within design parameters of the system. The generator is therefore abstracted from abrupt load variations. DC blending of sources are just the perfect way nature intended. I would actually suggest the opposite in that you set the rectifier to a voltage that is lower than the inverter charger. This is maybe required as to not interfere with the transaction between bms and inverter. A pedantic bms or pedantic inverter might abort operation if the actual charge voltage is higher than that negotiated. But this I have not witnessed in practice. Maybe @Coulomb can give us his thoughts here.
  9. Slightly offtopic, with a rectifier dc couplled solution where you connect your mains also to such rectifier, you get 0mS transfer to load when mains fail, very solid and reliable solution for critical loads. Only downside is a bit of loss of efficiency.
  10. DC coupling solution for the high voltage batteries might be tricky. I know Atess has a rectifier cabinet for DC coupling, but thats probably very expensive. If its LV (48V) I would consider a hybrid inverter for this purpose.
  11. Agree, especially error 09 where you running a business and required to provide a reasonable warranty, then main board replacement is a given. The good news is a new OEM board escalates the machine to status of 'new' again.
  12. @GerhardK83 has pretty much nailed it as far as my opinion is concerned. There exists no diagnostic tool for most of the inverters on SA market that I am aware of. While we in the community have devised methodologies and walkthroughs to assist in repairs, they remain casual and informal as far as business practices are concerned. Almost all inverters are not modular for economical reasons. Therefore they typically have a single main board which account for about 80% of the function. The controller is typically seperate and its interfaces to the main board only allows for critical diagnostics during startup, example soft start evaluation. But it cannot pinpoint the components /subsystems on the mainboards that may be faulty. As Gerhardt pointed out, the agents/distributors can therefore only support and repair inverters on board level. The cost of a new main board may easily attribute to 40% of the value of the inverter. The OEM provides no schematics and documentation for field and repair personnell, other than a service manual that, in my opinion, is grossly inadequate for purpose.
  13. Hi Chris, welcome to the forum. What exactly do you mean by assess? To test / verify them.? Almost all of today's modern inverters are equipped with user interfaces (text/graphics mode) that not only allow settings but exposes its modes and status of operation. It also reports warnings and errors.
  14. Hi Coulomb, a bit offtopic. Your AUS site has a very attractive looking appearance. Is that a new engine or merely a config/cosmetic update?
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