Due to increases in switching frequency, the electromagnetic interference of motor drive systems has been receiving more attention. In a motor drive system, the devices in the inverter produce serious electromagnetic interference during high-frequency switching. It is necessary to model the motor drive system to predict the electromagnetic interference level. Extraction of the motor impedance characteristic is necessary for the modeling of a motor drive system. At present, most research only studies the measurement method of a motor in the static state. However, motor impedance characteristics in the static state cannot represent motor impedance characteristics in operation. In this paper, an online measurement method of motor impedance characteristics is proposed. For the three-phase asymmetric circuit caused by modulation, the motor impedance characteristics in operation are calculated by establishing Kirchhoff voltage equations. A precision power scope PX8000 is used to measure the harmonic components of single-phase voltage, single-phase current, and common-mode current. The time-delay difference of the precision power scope PX8000 between different probes is also considered. Experiments prove that the time-delay difference does not affect the measurement results. Through comparing the motor impedance characteristics measured by different filters, the method of extracting the motor impedance characteristics online is validated. Finally, the motor impedance characteristics in the static state and the motor impedance characteristics of online extraction are experimentally compared. The motor impedance characteristics of the online extraction method proposed in this paper have more advantages than traditional methods.

由于开关频率的增加，电动机驱动系统的电磁干扰受到了越来越多的关注。在电动机驱动系统中，逆变器中的设备会在高频切换期间产生严重的电磁干扰。有必要对电动机驱动系统进行建模以预测电磁干扰水平。电动机阻抗特性的提取对于电动机驱动系统的建模是必要的。目前，大多数研究仅研究静态电动机的测量方法。但是，静止状态下的电动机阻抗特性不能表示运转中的电动机阻抗特性。本文提出了一种在线测量电动机阻抗特性的方法。对于由调制引起的三相不对称电路，通过建立基尔霍夫电压方程来计算运行中的电动机阻抗特性。精密功率示波器PX8000用于测量单相电压，单相电流和共模电流的谐波分量。还考虑了不同探头之间的精密功率示波器PX8000的时延差异。实验证明，时延差异不影响测量结果。通过比较不同滤波器测得的电动机阻抗特性，验证了在线提取电动机阻抗特性的方法。最后，通过实验比较了静态时的电动机阻抗特性和在线提取的电动机阻抗特性。