Reliable Detection of Armature Fault in Brushless Exciters With m-Phase Toroidal Winding Using Search-Coil Voltage and Field Current Signature Analysis

In the operation of nuclear power plants, the fast, sensitive, and reliable diagnosis of rotating armature winding short circuit (AWSC) faults in m-phase toroidal brushless exciters (mPTBEs) is crucial. Traditional diagnosis approaches based on stator field current signature analysis (FCSA) are widely used on site due to their noninvasive nature. However, on-site operational experience has shown that this method may be influenced by fault transient processes and interference from the excitation current. To address these issues, this article proposes a novel AWSC fault diagnosis method that integrates a search coil (SC) and field current. By combining the ability of SC to capture spatial fractional magnetic field changes, the comprehensive fault characteristics can be obtained. To ensure immunity to field current interference, a blocking criterion is presented based on the ratio of fractional harmonics to integer harmonics in the SC electromotive force (EMF). Additionally, a criterion for abnormal operation based on the fault EMF features is also presented to assist FCSA in rapid diagnosis and sensitive warning. The effectiveness of the proposed method is verified through experiments on an 11-phase prototype, which demonstrates that the combination of FCSA and SC can effectively improve the diagnosis performance of AWSC faults.