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| Inverter drive module overvolt fault |
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| capt bullshot:
--- Quote from: Eamon on October 12, 2022, 04:24:03 am --- --- Quote from: WattsThat on October 12, 2022, 02:48:41 am ---Is there any feedback from the motor back to the inverter? Some motors use three Hall effect sensors to tell the inverter where the rotor is, needed for proper switching. If there are no sensors/feedback, it should run with a resistive load so long as the current is close to that of the compressor load. --- End quote --- No, the motor has only three wires, the three power phases from the inverter. --- End quote --- My conclusion from this and other observations is - there's some kind of synchronous motor inside the compressor, and the inverter uses "sensorless feedback" for its control loop. The inverter won't run with anything else than a similar synchronous (PMSM) motor. Is 320V above the peak value of your normal mains AC voltate (e.g. 230V * 1.414 -> 325V)? If the PFC is active, the voltage from DC+ to DC- should be larger than this value. In practice, the rectified voltage from mains is somewhat smaller than this theoretical value, so 320V could mean the PFC isn't active. I'd expect 350V (ballpark value) while the PFC is active. If there's something wrong with the compressor, causing it to feed back energy into the DC-Link, voltage could easily rise up to 380V ... 400V before an error message is thrown. This is at least some general figures, I've got no experience with this particular appliance. |
| Eamon:
--- Quote from: capt bullshot on October 12, 2022, 05:49:53 am ---My conclusion from this and other observations is - there's some kind of synchronous motor inside the compressor, and the inverter uses "sensorless feedback" for its control loop. The inverter won't run with anything else than a similar synchronous (PMSM) motor. Is 320V above the peak value of your normal mains AC voltate (e.g. 230V * 1.414 -> 325V)? If the PFC is active, the voltage from DC+ to DC- should be larger than this value. In practice, the rectified voltage from mains is somewhat smaller than this theoretical value, so 320V could mean the PFC isn't active. I'd expect 350V (ballpark value) while the PFC is active. If there's something wrong with the compressor, causing it to feed back energy into the DC-Link, voltage could easily rise up to 380V ... 400V before an error message is thrown. This is at least some general figures, I've got no experience with this particular appliance. --- End quote --- You are probably right about the motor but for all intents and purposes the fact that this is a heat pump and that the load is a compressor is irrelevant to the problem at hand I believe; this is a variable frequency driver for a 3 phase motor that uses as you said "sensorless feedback". I agree that I'm unlikely to have much luck using anything other than the actual compressor it is built for as a load. In any case, there's a real chance that a different load might not exhibit the fault for various reasons and ultimately I need it to work with the compressor not some other load so I'm somewhat resolved to do my testing in place at the appliance even though that is outdoors and means a bit of setup and packing up each time I want to take some measurements. My nominal AC voltage is "230 volts +6/-2%" according to regulations. In practice I see it vary a bit throughout the day (there is a high penetration of roof top solar where I live, including my own house). What I measured with the multimeter (BM796) this morning was nearly bang on 230v. I was playing around a little with the Analog Discovery 2 USB scope and the 100x probes at my desk. When I put them across active-neutral, the AC signal was not a pure sine wave; it appeared somewhat clipped. Image attached. I don't think this is likely to be a contributing factor to the fault, just that it might mean the peak DC voltage would be a little different than expected for pure sine wave 230v RMS signal. Over about 5 minutes I recorded a range 225V-233V, my multimeter recorded almost exactly 1V less. max and min are also recorded in the image. |
| capt bullshot:
Your 230V waveform looks pretty normal. It's not an ideal sine wave, but rather a bit "clipped" as you see. This is the reason why I said, the actual peak voltage is lower than the theoretical value. A "short" (up to maybe 5...10m) cable from the inverter to the compressor/motor most probably works, at least for testing purposes. |
| florentbr:
--- Quote ---though DB2 does not seem to have a reciprocal part in the diagram --- End quote --- Check this one: https://www.ti.com/lit/ug/tidu249/tidu249.pdf --- Quote ---How high is "well over"? I double checked the +vDC plane several times with the multimeter in DC mode and the highest I have seen is about 325V. --- End quote --- I don't know how much higher it's supposed to be. All the PFC I've tested were around 370v (small SMPS) and all the literature I came across is showing a significant difference between Vmax input voltage and output DC. If you check the previous pdf, there's an example at the end showing Vrms=230V and Vbus=390V (DC-link). This paper says that it must have an output voltage greater than 380v: https://www.ti.com/seclit/ml/slup390/slup390.pdf --- Quote ---Is there something I can do with a multimeter to check if the PFC circuit is turning on? --- End quote --- To determine if the PFC is ON, measure the voltage or frequency at the transistor's gate. You should measure something even if the frequency is too high. --- Quote ---My thoughts are similar; the reported AC voltage when it jumps is almost exactly the same as the reported DC voltage, i'm just not sure where to measure to test that theory. --- End quote --- Measure the DC voltage at the output of the bridge rectifier and at the output of the PFC (DC-link). --- Quote ---if the problem is the +DC leaking back to the output of the bridge rectifier, it would seem that C53A could cause that? --- End quote --- If C53A was defective, it could have an impact on the measured voltage at the output of the bridge rectifier. I have no explanation for the InverterPlateACVoltage switching between 225v, 320v and 255v. If there was a path back to the rectifier, the InverterPlateACVoltage should be the same as InverterDCVoltage, on standby or PFC on. It's not the case and your curve shows 3 distinctive states. |
| Eamon:
--- Quote from: capt bullshot on October 12, 2022, 12:34:05 pm ---A "short" (up to maybe 5...10m) cable from the inverter to the compressor/motor most probably works, at least for testing purposes. --- End quote --- :palm: I hadn't even considered a longer cable |O. The run will be more like 30m but it's worth a shot. |
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