ASD system condition monitoring using cross bicoherence

In this paper, we propose a novel condition monitoring method for adjustable speed drives (ASD) and ASD-driven motors. The key idea is to diagnose the status of the load side of an ASD from observations made at the source side. The use of a higher-order spectral metric, the cross bicoherence, is proposed for the detection and analysis of anomalies associated with nonlinear devices in ASD systems. In this paper, we apply our method to detect phase imbalance at the load side of an ASD. Our experimental results demonstrate that the proposed method provides a unique signature of phase imbalance for detection and classification of asymmetric impedance associated with the phase imbalance. Furthermore, the proposed method shows a more sensitive detection performance compared to the conventional imbalance measurement method, which enables early detection of potential faults.