Maintenance technicians are no strangers to variable-frequency drives, this type of industrial control electronic equipment. In our daily work, we inevitably encounter faults with these drives. Here are diagnostic and repair methods for variable-frequency drive issues—hope they are helpful! Let's take a look below!
VFD Fault Diagnosis and Repair
1. First, read the fault codes from the converter display. The coding information for each converter varies, but basic fault records typically include overcurrent, overvoltage, overload, overtemperature, loss of analog, and loss of communication. Historical faults for the ABB-ACS550 variable frequency drive can be found through the 04 group of parameters. At the same time, we can determine general faults by the panel indicator lights turning red.
2. Through fault analysis of actual inverter test data, we verify the actual switch signal, analog signal, and actual inverter operation data. The parameter group can perform signal detection on the ABB-ACS550 converter. Additionally, attention must be given to the rationality of the inverter's characteristic parameter settings, particularly the U/F curve, acceleration/deceleration time, current limiting, and various protections.
VFD Fault Diagnosis and Repair Methods:
1. Siemens Variable Frequency Drives
The general cause of a black screen is due to power damage or internal burnout caused by IGBT short circuits. Fault symptoms for the 6se7016-1ta61-z model: The control panel PMU LCD display is not showing any indication. Upon testing with a 24V external power supply, the screen displays normally. However, when measuring the low-voltage AC output with a multimeter, no voltage indication is present, indicating a fault. The pulse output at the uc3844 (6) pin is normal, but there is no signal at the q36 anode. Measurement of r321 shows a change from 28 ohms to infinite, and the fault is resolved.
2. Delta VFD
The cause of the failure was a malfunction in the converter's output. Inspection revealed a fractured IGBT inverter module and severely damaged driver circuit PCB. Firstly, the damaged IGBT inverter module was disassembled. During the disassembly process, care should be taken to protect the PCB to prevent secondary damage. Damaged electronic components in the transmission line had to be replaced one by one, and open circuits on the PCB were connected with wires (note to scrape off the charred parts to prevent re-ignition).
Six drive circuit resistors were the same, and the voltages were equal; waveforms were measured using an oscilloscope. However, upon turning on the converter, an OCC fault was reported (the Delta VFD lacks an IGBT inverter module, and the startup will alarm). The P1 module was connected to the board light, while others were connected to cables; the machine was started again. The issue with the drive circuit was identified, and individual optocouplers were replaced, eventually discovering that the optocouplers in the drive circuit had a detection function, with one of them being damaged. After replacement, the machine started up normally.
3. Fuji G9 Inverter
The Fujitsu G9 converter is currently not displaying any faults. The receiver estimates that the issue might be a damaged switch power supply in the inverter. Upon opening the inverter and inspecting the switch power supply lines, no damage to the switch power supply components was found. There was no display of DC positive and negative voltages. It is estimated that the problem may be related to the driver. After inspecting all capacitors in the driver circuit, it was discovered that some were leaking. New electrolytic capacitors were installed, and the converter is now functioning normally.
Above is the content regarding the requirements for fault diagnosis and maintenance of inverters. For more information on related knowledge, please stay tuned for our future article updates!
