Abstract：The common-mode voltage output by the inverter drive motor system, through the coupling of the motor capacitances, induces bearing voltage, which causes electrical corrosion of the bearing and endangers the operation of the motors. In the frequency conversion drive system, the frequency converter and the motor are generally connected by cables. There are different types of cables, such as shielded and unshielded cables. The type and length of cables affect their equivalent electrical parameters. The influence of cable parameters on the bearing voltage is currently unclear, and the key parameters of the cable that affect the motor bearing voltage are still uncertain. This paper analyzes the influence of the cable type and length on bearing voltage, providing a basis for the design and selection of the cable of the frequency conversion system to suppress the bearing current and bearing voltage. Firstly, the mechanism of high-frequency bearing current generation of the motor in the variable frequency drive system is analyzed, and the common-mode equivalent model of the motor and cable system is established. Secondly, taking a 5.5 kW induction motor as an example, the electrical model parameters of the cable and motor are extracted through the impedance test curve. The impedance characteristics of the cable and motor composition system are verified. An unshielded cable with 3 m, a shielded cable with 3 m, and a shielded cable with 10 m are compared. The influence of the cable type and length on motor bearing voltage and bearing current is studied through circuit simulation. Finally, a bearing current test platform is built, and the accuracy of the model and the correctness of the simulation analysis are verified. The corresponding suppression scheme is given for the motor bearing voltage and bearing current problems of the frequency conversion drive system. According to the simulation results, compared with the 3 m unshielded cable, the stator ground current of the 3 m shielded cable increases by nearly 25%, and the bearing voltage and bearing current decrease by 5%. When the length of the shielded cable increases from 3 m to 10 m, the bearing voltage is reduced by 11%, but the stator ground current is increased by 14%. The test results are similar to the simulation results. Increasing the shielded cable or length reduces the bearing voltage and bearing current and increases the stator ground current. The motor circulating bearing voltage of the 3 m shielded cable is increased by 21% compared to the 3 m unshielded cable. The increase of cable parasitic capacitance mainly causes the decrease of the motor bearing voltage and bearing current. The following conclusions can be drawn from simulation and test results. (1) Increasing the parasitic capacitance parameter can reduce the motor bearing voltage and bearing current. Cable parasitic capacitance is the key parameter. (2) Compared with unshielded cables, shielded cables increase the parasitic capacitance parameters of the cable and reduce the impedance of the common-mode circuit, leading to the increased stator ground current and the circulating bearing voltage. (3) For the cables that length does not cause voltage reflection, long cables increase the stator ground current but decrease the bearing voltage and bearing current.
陈立珂, 刘瑞芳, 李知浩, 张亮亮, 李伟力. 电缆参数对变频驱动电机轴电压和轴电流的影响[J]. 电工技术学报, 2024, 39(15): 4755-4766.
Chen Like, Liu Ruifang, Li Zhihao, Zhang Liangliang, Li Weili. The Influence of Cable Parameters on the Bearing Voltage and Bearing Current of the Variable Frequency Drive Motor. Transactions of China Electrotechnical Society, 2024, 39(15): 4755-4766.
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