Open-Circuit Fault Diagnosis for Dual Three-Phase Permanent Magnet Machine Considering Nonideal Condition

Nonideal currents, such as unbalanced current and nonsinusoidal current, greatly challenge the open-circuit fault diagnosis by increasing the risk of false alarms. In this article, an open-circuit fault diagnostic method based on vector space decomposition transformation is proposed for surface-mounted dual three-phase permanent magnet machine drives, which is simple, fast, and most importantly, robust to nonideal currents. The proposed method divides per-phase current into direct-axis and residual components, and then, the ratio of both can be utilized for open-circuit fault detection and identification, including open-switch and open-phase faults, which are relatively simple to implement. Benefited from universal i(d) = 0 control, the proposed fault index remains at zero under healthy condition and is not influenced by machine parameter, operation conditions, and nonideal cases, thus reducing the risk of false alarms. Moreover, the natural robustness allows a low security margin for fast diagnostic speed. Experimental results verify the robustness and effectiveness of the proposed method.