Inverter failure?
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The set frequency of the inverter is 45HZ, but the actual frequency of the inverter fluctuates within the range of 30HZ to 38HZ to 45HZ, which makes it impossible to control the pump flow rate. What is the reason for this? Thank you to all the sea friends.
If it is a potentiometer input, it is likely that the potentiometer has poor contact. If it’s a panel input, move the panel plug, or try replacing the panel.
The set frequency of the inverter is 45HZ, but the actual frequency of the inverter fluctuates within the range of 30HZ to 38HZ to 45HZ, which makes it impossible to control the pump flow rate. May I ask: Where can I check the actual frequency of the inverter? Is it on the inverter panel? Still the monitoring backend? If it is the former, it indicates that the output frequency of the inverter is indeed fluctuating. It might be that the potentiometer’s contacts are not in good condition. If it is the latter, it may be that the 4-20mA signal sent by the inverter to the backend has been interfered with.
It is also possible that the 4–20mA control signal has been interfered with.
This post was last edited by zhaohh3211 on 2010-7-28 at 16:15. I agree with the opinion of the poster on the third floor; one could measure the frequency at the motor side to see if there is indeed fluctuation. It might also be necessary to implement closed-loop control by adding a feedback signal.
The main issue is likely related to the signals; check the input signal and the feedback signal. Some frequency converters use 0-10V signals, while others use 4-20mA signals. Regardless of the type, the frequency set should not fluctuate. Use a multimeter to measure it; if there are still problems, try running the motor without a load. If issues persist, then it’s a problem with the frequency converter’s main board, which requires further investigation.
I agree with the views of those above. Another possibility that can cause the pump flow to be uncontrollable is cavitation in the pump. Try increasing the inlet valve or reducing the outlet valve. Check if the frequency of the inverter is changing
Verify how to control frequency conversion； If it is a resistor, its condition should be checked. If a 4–20mA signal is provided via DCS, the cause should be sought in the path through which this signal is generated and transmitted; possible reasons include an unstable signal source or interference along the transmission path ； Transmission path interference may be caused by electromagnetic interference resulting from improper cable installation, or by poor grounding of the same cable being used to carry multiple signals.
The main possible cause is interference with the current signal used to regulate the speed; another reason is improper setting of the PID control parameters inside the frequency converter.
This post was last edited by zhaohh3211 on 2010-7-28 at 16:24. Under normal circumstances, there should be no problems with the frequency converter; it’s very likely that the 4–20mA signal is affected by interference, which in turn causes the frequency converter to receive inconsistent signals and thus fluctuate erratically!