Inverter field debugging and troubleshooting - Database & Sql Blog Articles

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1. Introduction

In the application of frequency converters, it's common to encounter commissioning and maintenance challenges. Faults caused by various reasons need to be addressed promptly. Correct debugging methods, timely fault detection, and accurate identification of the root cause are essential. Beyond theoretical knowledge, two key qualities are required: familiarity with the product and accumulated practical experience in debugging, maintenance, and troubleshooting. These hands-on experiences are developed through real-world practice and continuous learning. Engaging with peers and exchanging insights is a great way to improve technical skills. I share my field experiences here to foster better communication among frequency converter professionals and contribute to collective growth.

2. Inverter and Host Computer Communication Fault Diagnosis and Resolution

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 upgrades. Each inverter was equipped with a DDC module from Canada for communication control. The upper computer managed the inverter’s fault alarms, filter network alerts, frequency, start/stop, and temperature monitoring. The user said that when disconnected from the upper computer, everything worked fine. However, when connected, the inverter would not stop even after the command was issued.

(2) Fault Analysis: Upon inspection, we found that the DDC module used a transistor output with DC 24V, while the inverter only accepted passive or switch signals. This mismatch caused the issue.

(3) Troubleshooting: Adding a DC 24V relay to the DDC module’s signal output resolved the problem.

2.2 Example 2

(1) Fault Phenomenon: A user reported that the inverter could run without the host computer but failed to operate when connected.

(2) Fault Analysis: Based on experience, the host computer sent a running signal, but the inverter didn’t receive it. We suspected a wiring issue and instructed the technician to re-route the lines carefully.

(3) Troubleshooting: After reconnection, the fault was resolved, indicating a loose one-way control line was the issue.

2.3 Example 3

(1) Fault Phenomenon: A dealer’s customer had a recurring fault with a Lenze 5.5kW inverter. It was sent for repair twice but still failed. The fault persisted even after returning to the company.

(2) Fault Analysis: The inverters were controlled via communication with the host computer, and many control lines were involved. High ambient temperature and lack of maintenance over several years led us to suspect short circuits or open circuits in the control lines.

(3) Troubleshooting: After removing all control lines and testing, we found two aged control lines had shorted. Replacing all control lines fixed the issue.

2.4 Example 4

(1) Fault Phenomenon: A CNC lathe operator reported that the touch screen often malfunctioned during operation, displaying a blue screen or turning off. Restarting the system temporarily resolved the issue, but the problem returned after a few minutes.

(2) Fault Analysis: After checking the inverter and wiring, we replaced the inverter, but the problem remained. Eventually, we discovered that poor grounding of the touch screen was causing interference.

(3) Troubleshooting: Fixing the grounding connection eliminated the interference, and the system ran smoothly afterward.

3. Inverter Installation Environment Fault Diagnosis and Resolution

3.1 Example 1

(1) Fault Phenomenon: A 55kW inverter reported an under-voltage error after more than a year of use. During testing, the contactor made a “beep” sound, and the 220V transformer and fans were damaged.

(2) Fault Cause: The AC fan and transformer were aged, and dust buildup in the air ducts caused poor contactor coupling. Maintaining a clean environment is crucial for inverter performance.

3.2 Example 2

(1) Fault Phenomenon: A 110kW inverter used in a textile factory experienced a control board burnout after some time. The dealer’s technician couldn’t resolve the issue.

(2) Fault Handling: After checking, we found a short circuit in the control line. Replacing the line restored normal operation.

(3) Fault Reason: Poor routing of the control line led to physical damage and short circuits.

3.3 Example 3

(1) Fault Phenomenon: A 160kW inverter in a coal mine had load protection issues, but no problems when unloaded. Output voltage was balanced, and the inverter was out of warranty.

(2) Fault Check: All external circuits and current measurements were normal. We eventually found a broken Hall sensor connection line.

(3) Fault Reason: The Hall sensor line was damaged due to vibration. Replacing it solved the problem.

(4) Handling Suggestions: Install inverters away from vibrating motors and ensure proper cable management.

3.4 Example 4

(1) Fault Phenomenon: A 15kW inverter overheated after a year of use. The user requested maintenance.

(2) Fault Analysis: Motor heat was checked, and insulation resistance tests revealed an issue with the original motor.

(3) Fault Reason: The motor had degraded insulation, not the inverter itself.

4. Inverter Interference Fault Diagnosis and Resolution

4.1 Example 1

(1) Fault Phenomenon: PLC-controlled inverters frequently generated false faults. Signals were not received, and malfunctions occurred.

(2) Fault Reason: Interference was suspected based on experience.

(3) Troubleshooting: Isolating power and control lines, and using shielded cables significantly reduced the issue.

4.2 Example 2

(1) Fault Phenomenon: Three inverters in a cabinet showed unstable speed control, with frequency fluctuations and protection trips.

(2) Fault Reason: Interference was the main cause. Separating inverters and using shielded cables resolved the issue.

4.3 Example 3

(1) Fault Phenomenon: Synchronous operation of two inverters triggered overcurrent faults. The issue was initially blamed on the inverter.

(2) Fault Reason: Poor grounding and interference from unshielded control lines were the causes.

(3) Troubleshooting: Shielded cables, magnetic rings, and proper grounding fixed the problem.

4.4 Example 4

(1) Fault Phenomenon: Three 15kW inverters occasionally triggered hardware protection errors.

(2) Fault Analysis: Shared zero-ground wiring caused interference. Removing the ground line resolved the issue.

4.5 Example 5

(1) Fault Phenomenon: A 3.7kW inverter on a weaving machine failed to drive the motor despite showing frequency display.

(2) Fault Analysis: Initial checks suggested no internal issues. We suspected interference.

(3) Troubleshooting: Using magnetic rings, shielded cables, and reducing carrier frequency resolved the issue.

5. Conclusion

The cases discussed highlight that most inverter faults are related to installation, environment, and wiring. Proper grounding, shielding, and regular maintenance are critical. When issues arise, it’s important to stay calm, analyze the symptoms, and systematically troubleshoot. With patience and attention to detail, every fault has a solution. Always refer to manuals, check connections, and seek peer advice when needed. Experience and careful observation are key to effective inverter diagnostics and resolution.