| Electronics > Repair |
| Inverter drive module overvolt fault |
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| Eamon:
--- Quote from: capt bullshot on October 08, 2022, 10:48:38 am ---Reading your first post again (didn't see the additional information at my first reply here) - I doubt "AC plate voltage" directly relates to the AC input voltage at all, and there might not exist any AC input voltage sensing circuit at all. Usually there's no need for such kind of inverter to monitor the AC input voltage, especially if it's just single phase (for three phase and higher power you want to monitor the input to detect a lost phase condition). I've got no idea what "AC plate voltage" means in this context, where's the origin of this term? --- End quote --- I mis-typed it slightly but "Inverter plate AC voltage" is the term the touchscreen uses. When I was reverse engineering the modbus protocol, I had the controller and touch screen connected to my computer acting as the Inverter module and would send back various values for the requested registers and see how they would represent in the touchscreen. One particular register always matches the value the touchscreen represented as "Inverter plate AC voltage", this is the value represented in the chart in the first post (I added the PCB back and the chart images a bit later). Also, the fault code reported in the touchscreen interface is "Inv. Input Overvolt." which is why I'm assuming it's a measure of the input AC voltage but I agree that there does not seem to be a need for such a measure. --- Quote from: capt bullshot on October 08, 2022, 10:48:38 am ---Do you have means to operate the inverter board at somewhat lower AC input voltage? Some kind of autotransformer or variac to reduce the mains voltage by some 10 Volts? One can use an ordinary e.g. mains input and 12V output transformer by some simple but tricky wiring to reduce the mains voltage by 12V - the 12V output winding just has to be able to supply the nominal current of the load, not the nominal power. --- End quote --- Are you suggesting running the inverter at a lower voltage permanently as a workaround or as part of diagnosing the problem? Could probably just drop the AC voltage by running about 50m of 2.5mm2 extension cable if it's just a test, wouldn't want to run it permanently like that though. |
| capt bullshot:
Yes, 100:1 probes could do the job as the AD has differential inputs anyway, and your setup should be safe. Just ensure to properly adjust and match them. "Inverter plate AC voltage" is as meaningless to me as "AC plate voltage", and the almighty internet doesn't give meaningful results, too. I guess it's some literal but not meaningful japanese/chinese/korean to English translation. Reducing the input voltage: My intent is for testing, to see whether the error message disappears or the measured value changes according to the change in input voltage. The extension cord won't drop the voltage in standby, so the latter one wouldn't work. |
| Eamon:
Well I tried to connect the motor in place of the compressor and while nothing blew up, the motor barely turns at a very slow speed with a bit of a high pitch for a second or two before the inverter faults out with a "PFC fault". Time to find a plan B for a load to replace the compressor. Can you give me some insight as to the 12v transformer trick to reduce the voltage? Also just occurred to me that I have an old stick welder that is essentially just a giant iron core variable step down transformer, turn a handle to move the secondary winding further into or out of the primary. I'll investigate what the voltage is on the lowest current setting.... |
| Eamon:
Well I don't think the welder will be useful directly as the maximum output voltage is ~45v with input of 236v, but it may be useful in place of a 12v transformer that you mentioned previously, it will certainly handle the current of the inverter and the load even. If you could provide some more details of the "some simple but tricky wiring" that would be helpful, in the meantime I'll google a bit and see what I can find. |
| florentbr:
This reminds me of an SMPS driver that was randomly shutting down. The waveform of the input rectified DC had voltage spikes, which I assume was causing an over-voltage shutdown (OVP). I removed the PFC switching transistor and the issue never reappeared. I didn't check the capacitors since the rectified DC under load was steady without the PFC. I suspect that the ESR of the capacitors went out of spec. In your case, the reported voltage seems to be correct when on standby, so I don't think it's a sensing issue. Since it takes an inductor to raise a voltage, I would pay attention to the PFC stage. Among those TO-264 you'll find a switching transistor and two diodes for the PFC. For more information, search for "PFC boost converter design guide". |
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