Burriel-Valencia Jordi, Puche-Panadero Ruben, Martinez-Roman Javier, Sapena-Bano Angel, Pineda-Sanchez Manuel
The authors are with the Institute for Energy Engineering, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain.
Sensors (Basel). 2019 Aug 8;19(16):3471. doi: 10.3390/s19163471.
Fault diagnosis of rotor asymmetries of IM using the stator current relies on the detection of the characteristic signatures of the fault harmonics in the current spectrum. In some scenarios, such as large induction machines running at a very low slip, or unloaded machines tested offline, this technique may fail. In these scenarios, the fault harmonics are very close to the frequency of the fundamental component, and have a low amplitude, so that they may remain undetected, buried under the fundamental's leakage, until the damage is severe. To avoid false positives, a proven approach is to search for the fault harmonics in the current envelope, instead of the current itself, because in this case the spectrum is free from the leakage of the fundamental. Besides, the fault harmonics appear at a very low frequency. Nevertheless, building the current spectrum is costly in terms of computing complexity, as in the case of the Hilbert transform, or hardware resources, as in the need for simultaneously sampling three stator currents in the case of the EPVA. In this work, a novel method is proposed to avoid this problem. It is based on sampling a phase current just twice per current cycle, with a fixed delay with respect to its zero crossings. It is shown that the spectrum of this reduced set of current samples contains the same fault harmonics as the spectrum of the full-length current envelope, despite using a minimal amount of computing resources. The proposed approach is cost-effective, because the computational requirements for building the current envelope are reduced to less than 1 % of those required by other conventional methods, in terms of storage and computing time. In this way, it can be implemented with low-cost embedded devices for on-line fault diagnosis. The proposed approach is introduced theoretically and validated experimentally, using a commercial induction motor with a broken bar under different load and supply conditions. Besides, the proposed approach has been implemented on a low-cost embedded device, which can be accessed on-line for remote fault diagnosis.
利用定子电流对感应电机转子不对称性进行故障诊断，依赖于检测电流频谱中故障谐波的特征信号。在某些情况下，如大型感应电机在极低转差率下运行，或离线测试的空载电机，这种技术可能会失效。在这些情况下，故障谐波非常接近基波分量的频率，且幅值较低，以至于它们可能一直未被检测到，被基波泄漏掩盖，直到损坏严重。为避免误报，一种行之有效的方法是在电流包络中搜索故障谐波，而非电流本身，因为在这种情况下频谱中没有基波泄漏。此外，故障谐波出现在非常低的频率处。然而，构建电流频谱在计算复杂度方面成本高昂，如在希尔伯特变换的情况下，或者在硬件资源方面成本高昂，如在采用扩展相量算法（EPVA）时需要同时采样三个定子电流的情况。在这项工作中，提出了一种新颖的方法来避免这个问题。它基于每个电流周期仅对相电流采样两次，相对于其过零点有固定延迟。结果表明，尽管使用了最少的计算资源，但这组简化的电流样本的频谱包含与全长电流包络频谱相同的故障谐波。所提出的方法具有成本效益，因为就存储和计算时间而言，构建电流包络的计算需求降低到其他传统方法所需的不到1%。通过这种方式，它可以用低成本的嵌入式设备实现在线故障诊断。本文从理论上介绍了所提出的方法，并在不同负载和供电条件下，使用一台有断条的商用感应电机进行了实验验证。此外，所提出的方法已在低成本嵌入式设备上实现，可在线访问进行远程故障诊断。
