Siemens inverter common fault analysis and processing - Database & Sql Blog Articles

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When dealing with a faulty inverter, the first step is to inspect the rectifier bridge and IGBT module using a multimeter before powering on. Make sure there are no visible signs of burning or damage on the circuit board. The process involves using a multimeter (preferably an analog one) set to the 1K ohm range. Connect the black probe to the DC negative terminal of the inverter and measure the resistance between the red probe and each of the three-phase input and output terminals. The resistance should be around 5K–10K ohms, and the readings for all three phases should be similar. The output resistance should be slightly lower than the input, and there should be no charging or discharging behavior. Repeat this by switching the probes: connect the red probe to the DC positive terminal and the black probe to the input and output terminals. Again, the resistance should fall within the same range, with consistent values across all phases. If any deviation is observed, it may indicate a damaged module.

If no issues are found during this initial test, you can proceed to power on the inverter. However, if the panel displays fault codes like [F231] or [F002] (for MM3 inverters), it could point to a power supply board issue, although a faulty main control board is also possible. Try replacing the main control board first. If that doesn’t resolve the issue, the problem likely lies with the power supply board.

If the panel shows no display after power-on (as in the case of MM4 inverters), and the green light does not illuminate while the yellow light flashes rapidly, it suggests that the rectifier and switching power supply are functioning normally, but there might be an issue with the switching power supply itself. This could involve a failed rectifier diode, which can be easily checked with a multimeter. A low diode withstand voltage or power supply ripple might cause this type of failure.

In some cases, the inverter may show error codes like [F0022, F0001, A0501]. These can often be resolved by checking the connectors, as loose or poor connections are common causes. Some units may have issues due to substandard RC components or soldering problems on the board.

If the inverter displays [-----] after power-on, it’s usually a sign of a faulty main control board. In most cases, replacing the main control board solves the problem. However, issues with the power board can also occur, especially if the main control board has been exposed to excessive electrical interference. Poor heat dissipation can also contribute to such failures.

An example of this occurred with a MM440-200kW inverter used in a cement plant. Due to high load inertia, the motor would only reach about 5Hz at start-up and trigger alarm [F0001]. Initially, it was thought to be a parameter setting issue. After correctly configuring the motor parameters, the problem seemed resolved. However, the inverter later failed again, displaying [-----]. Upon inspection, it was found that the main control board had been damaged due to improper installation—specifically, strong and weak electricity were not properly separated, grounding was poor, and shielding cables were not used. This led to the I/O port being burned out. Replacing the main control board fixed the issue.

If the inverter powers on normally but shows overcurrent during operation (e.g., [F0001] for MM4 or [F002] for MM3), it typically indicates a damaged IGBT module or a problem with the drive board. It’s essential to replace the IGBT module and carefully check the drive section before re-powering the system. Otherwise, repeated overloads or unstable power supply voltages (especially low voltages) can cause the IGBT to fail again.

There are also less common but meaningful faults. For instance, a MM3-30KW inverter that frequently stops without reason may have an issue with the main contactor. Sometimes, the contactor loses power or fails to engage properly. This could be caused by leakage from the switching power supply filter capacitor into the contactor’s power supply, leading to intermittent shutdowns. If the voltage is too low, the contactor may not close properly, causing unexpected stops.

Another example involved a MM4-22KW inverter. After power-on, the display showed normal results, but when the operation signal was given, it displayed [P----] or [-----]. Upon closer inspection, the fan speed appeared abnormal. When the fan was disconnected, the inverter showed [F0030]. During maintenance, other errors like [F0021], [F0001], or [A0501] occasionally appeared. After testing, it was found that the issue stemmed from a leaking filter capacitor in the switching power supply. Replacing the capacitor resolved the problem.

A 75kW MM440 inverter in a steel plant ran smoothly initially but then stopped after half an hour. The inverter still maintained the running signal, and the panel displayed [A0922] (no load). Measuring the three-phase output voltage showed normal results when manually stopped. However, after more than 20 minutes, the output current dropped to just 0.6A. Further analysis revealed a fault in the current detection unit on the drive board. Replacing the drive board solved the issue.

In summary, while large components like IGBT modules are not the primary cause of most inverter failures, simpler issues such as faulty capacitors, poor assembly, or incorrect settings often lead to problems. With proper documentation and spare parts, these issues are generally easy to fix at a low cost. However, if drawings or components are unavailable, troubleshooting can become challenging. In many cases, replacing the entire board is the quickest and most effective solution.