1. Introduction
In the application of frequency converters, it is common to face commissioning and maintenance challenges. Faults caused by various reasons need to be resolved promptly. Correct debugging methods, timely fault detection, and accurate identification of causes are essential. In addition to theoretical knowledge, two key qualities are required: familiarity with the product and accumulated practical experience in debugging, maintenance, and troubleshooting. These experiences are gained through real-world work and continuous learning. Engaging with peers and sharing insights is also a great way to enhance technical skills. I hope this article will help others in the field of frequency converters improve their understanding and foster better technical communication. 2. Fault Diagnosis and Elimination for Inverter and Host Computer Communication
2.1 Example 1
(1) Fault Phenomenon: A customer reported an issue with 40 sets of 22kW fans in a factory workshop undergoing energy-saving renovation. Each inverter was equipped with a DDC module for communication control (imported from Canada). The upper computer controlled the inverter's fault alarms, filter network status, frequency, start/stop commands, and temperature. The user mentioned that when disconnected from the host computer, the system ran normally. However, when connected, the inverter could not stop even after the host computer issued a stop command.
(2) Fault Analysis: Upon inspection, the DDC module used a transistor output with DC 24V, while the inverter only accepted passive signals or switch signals. This mismatch caused the problem.
(3) Troubleshooting: Adding a DC 24V relay to the DDC output solved the issue.
2.2 Example 2
(1) Fault Phenomenon: The user reported that the inverter would run without the host computer but couldn’t be operated when connected.
(2) Fault Analysis: Based on experience, the issue was likely a wiring problem. The user was instructed to rewire the lines.
(3) Troubleshooting: After checking, the technician found that a one-way control line was loosely connected. Once fixed, the problem was resolved.
2.3 Example 3
(1) Fault Phenomenon: A dealer’s client had a recurring fault with a Lenze 5.5kW inverter. It had been sent for repair twice without success.
(2) Fault Analysis: The inverters were all controlled via communication, and the site environment was hot with old wiring. Removing the control lines and running the inverter without load showed normal operation. But once the control lines were connected, the inverter tripped.
(3) Troubleshooting: Measuring the control lines revealed two aged and shorted cables. Replacing all control lines restored normal function.
2.4 Example 4
(1) Fault Phenomenon: A CNC lathe’s touch screen interfered with the inverter, causing frequent screen malfunctions. Turning off and restarting the system temporarily fixed the issue, but it recurred.
(2) Fault Analysis: After checking, the wiring and inverter were normal. Replacing the inverter and control lines didn’t resolve the issue. Finally, removing the touch screen’s ground wire eliminated the interference.
(3) Troubleshooting: Poor grounding was the cause. After fixing the grounding, the system operated smoothly.
3. Fault Diagnosis and Elimination for Inverter Installation Environment
3.1 Example 1
(1) Fault Phenomenon: A 55kW inverter reported under-voltage after over a year of use. The internal 220V transformer and fans were damaged.
(2) Fault Cause: Aging of the AC fan and transformer led to poor contactor coupling. Dust and oil buildup in the air duct contributed to the failure.
(3) Conclusion: Maintaining a clean and cool environment is crucial for inverter performance.
3.2 Example 2
(1) Fault Phenomenon: A 110kW inverter used on an air compressor experienced a control board burnout.
(2) Fault Handling: Checking the wiring revealed a short circuit in the control line. Replacing the line restored normal function.
(3) Fault Reason: The control line was improperly routed along the ground, leading to damage and a short circuit.
3.3 Example 3
(1) Fault Phenomenon: A 160kW inverter in a coal mine had load protection issues. No faults were detected during no-load testing.
(2) Fault Check: All external circuits and measurements were normal.
(3) Fault Reason: A broken Hall sensor connection line was the culprit. Replacing the line resolved the issue.
(4) Suggestion: Vibration in the installation area may contribute to such failures.
3.4 Example 4
(1) Fault Phenomenon: A 15kW inverter overheated after a year of use.
(2) Fault Analysis: The motor was also overheating. Insulation resistance tests showed the motor was faulty.
(3) Fault Reason: The original motor had degraded insulation, leading to overheating.
4. Fault Diagnosis and Elimination for Inverter Interference
4.1 Example 1
(1) Fault Phenomenon: PLC-controlled inverters frequently reported unnecessary faults.
(2) Fault Reason: Interference was suspected.
(3) Troubleshooting: Separating power and control lines and adding shielding reduced the interference.
4.2 Example 2
(1) Fault Phenomenon: Three inverters in a cabinet caused frequency fluctuations.
(2) Fault Reason: Interference between inverters was the cause.
(3) Troubleshooting: Moving inverters to separate cabinets and using shielded cables resolved the issue.
4.3 Example 3
(1) Fault Phenomenon: Synchronous operation of two inverters caused overcurrent faults.
(2) Fault Reason: Poor grounding and interference were the main issues.
(3) Troubleshooting: Shielding control lines, adding magnetic rings, and proper grounding resolved the problem.
4.4 Example 4
(1) Fault Phenomenon: Three 15kW inverters reported "hardware protection" faults intermittently.
(2) Fault Analysis: Shared neutral and ground wiring caused interference.
(3) Troubleshooting: Disconnecting the shared ground line eliminated the issue.
4.5 Example 5
(1) Fault Phenomenon: A 3.7kW inverter on a bell weaving machine failed to drive the motor despite showing frequency.
(2) Fault Analysis: Interference was suspected.
(3) Troubleshooting: Adding magnetic rings, replacing control lines, and reducing carrier frequency resolved the issue.
5. Conclusion
From the cases discussed, most inverter faults are related to installation conditions and environmental factors. Proper grounding, shielding, and regular maintenance are essential. When problems arise, a systematic approach—starting with the symptoms and following the manual—can lead to effective solutions. Don’t panic; stay calm and methodically troubleshoot. With patience and attention to detail, every fault can be resolved.
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