A chemical fiber filament drawing production line consists of three drafting machines, each driven by separate motors. The first roller motor has a power of 22KW, 4-pole, worm reducer, and a speed ratio of 25:1. The second roller motor is 37KW, 4-pole, worm reducer, with a speed ratio of 16:1. The third roller motor is 45KW, cylindrical gear reduction, with a speed ratio of 6:1. These motors are driven by Huawei TD2000-22KW, IHF37K, and IHF45K inverters. The three inverters are controlled proportionally based on the draft ratio and speed ratio. The process works as follows: the tow is wound onto the first, second, and third rolls, and the frequency converter adjusts the speed between the rolls to achieve the desired drafting effect.
Initially, when the system was running with a low draft ratio, everything functioned smoothly. However, after some time in production, the process was adjusted, increasing both the draft ratio and the total denier of the tow. This change significantly increased the drag force on the rolls. As a result, the one-roll inverter started to frequently display an SC (overvoltage protection) error. Occasionally, the two-roll inverter also experienced similar issues, and eventually, the one-roll inverter would stop with an E006 (overvoltage) fault.
Upon detailed analysis, it became clear that the first roll's inverter was not handling the regenerative energy generated by the motor effectively. Since the draft ratio between the first and second rolls accounts for about 70% of the total, and the second and third rolls have higher power, the first and second rollers often operate in a regenerative or braking mode. The third roller, however, only runs in the electric mode. If the inverter cannot manage this regenerative energy, it will lack sufficient braking torque, leading to "dragging" from the other rolls.
The inverter attempts to reduce the overvoltage by increasing the output frequency, but when the regenerative energy is too high, this approach fails. Therefore, the main issue lies in ensuring that the first and second roller motors can generate enough braking torque. While increasing the motor and inverter capacity could solve the problem, it would be inefficient and costly. Instead, adding external brake units to the first and second roller inverters proved to be a more practical solution.
After testing, two sets of Huawei TDB-4C01-0300 brake components were installed. The results showed that the braking force, especially from the first roller resistor, was very effective. This confirmed our analysis. Since implementing these changes, the system has been operating smoothly for nearly a year without any overvoltage issues.
This case highlights the importance of understanding and managing regenerative energy in industrial systems. By addressing the root cause—ensuring proper braking torque through external brake units—we successfully solved the overvoltage problem. It also emphasizes the value of regenerative braking in maintaining system stability and efficiency. Properly managing this energy not only prevents faults but also improves overall performance and longevity of the equipment.
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Xuzhou Jiuli Electronics Co., Ltd , https://www.xzjiulielectronic.com