Vibration is the vital feature of the motor to diagnose various faults. The existing methods have many limitations. This work proposes a non-invasive Software Phase Locked Loop (SPLL) technique to diagnose the multiple rotor faults. A high-frequency (10.525GHz) microwave signal is projected on the motor and the reflected signal is captured by the handheld ultra-wide band (UWB) radar. Hardware filter is replaced by a software phase locked loop filter to remove high-frequency noise content in the signal. The output of the SPLL is analysed with Rational Dilation Wavelet Transforms (RDWT) and compared the change in the signal energy of the wavelet sub-band 6 for the multiple rotor bar faults and sub-bands 6 and 7 for the combination of rotor bar and bearing faults, respectively. The signal energy at sub-band 6 increased from 2.19% without fault to 3.99%, 6.03% and 13.66% with an increase in the number of rotor bars with faults. The variation of the experimental values of the signal energy for rotor bar faults compared with the theoretical values found that the error is reduced and accuracy is increased with the number of faults. For simultaneous rotor bar and bearing faults, the signal energy at sub-bands 6 and 7 also increases. The proposed SPLL-based method that is able to diagnose the individual faults and combination of the faults and has advantages such as simple, cost-effective and non-invasive technique compared with the existing methods.

振动是电机诊断各种故障的重要特征。现有方法有很多局限性。这项工作提出了一种非侵入式软件锁相环 (SPLL) 技术来诊断多转子故障。高频 (10.525GHz) 微波信号投射到电机上，反射信号被手持式超宽带 (UWB) 雷达捕获。硬件滤波器被软件锁相环滤波器取代，以去除信号中的高频噪声内容。使用有理膨胀小波变换 (RDWT) 分析 SPLL 的输出，并比较多个转子条故障的小波子带 6 和转子条组合的子带 6 和 7 的信号能量变化。轴承故障，分别。子带 6 的信号能量从无故障的 2.19% 增加到 3。99%、6.03% 和 13.66% 随着故障转子条数的增加。转子条故障信号能量的实验值与理论值相比的变化发现，随着故障次数的增加，误差减小，精度提高。对于同时发生的转子条和轴承故障，子频带 6 和 7 的信号能量也会增加。所提出的基于 SPLL 的方法能够诊断单个故障和故障组合，与现有方法相比具有简单、成本有效和非侵入性技术等优点。转子条故障信号能量的实验值与理论值相比的变化发现，随着故障次数的增加，误差减小，精度提高。对于同时发生的转子条和轴承故障，子频带 6 和 7 的信号能量也会增加。所提出的基于 SPLL 的方法能够诊断单个故障和故障组合，与现有方法相比具有简单、成本有效和非侵入性技术等优点。转子条故障信号能量的实验值与理论值相比的变化发现，随着故障次数的增加，误差减小，精度提高。对于同时发生的转子条和轴承故障，子频带 6 和 7 的信号能量也会增加。所提出的基于 SPLL 的方法能够诊断单个故障和故障组合，与现有方法相比具有简单、成本有效和非侵入性技术等优点。