Online Detecting Magnet Defect Fault in PMSG With Magnetic Sensing

Recently, detecting the magnet defect fault in permanent magnet synchronous generators (PMSGs) is still challenging. The previous work mainly focuses on the phase current, back electromotive force, or searching coils. However, these methods are sometimes limited due to the machine configuration, being computationally complex, or even being intrusive to the system. This article presents a new method for the online detection of the magnet defect in a PMSG simultaneously. This method is based on the leakage flux outside the generator, which is noninvasive. In the practical application, the leakage flux is measured by magnetic sensors mounted outside a PMSG under various operating conditions. First, the external leakage flux is derived theoretically with the magnetic equivalent circuit when one defective rotor magnet exists in a PMSG. Then, the external leakage flux is proved to contain information about the health condition of inside magnets during the machine operation. Subsequently, the permanent magnet defect indicator
$F_{\mathrm {ind}}$
is proposed for analyzing the condition of the rotor magnets in detail. Finally, both simulation and experiment results verify the efficacy of the proposed method.