Measurement and Analysis of Rotating Magnetic Field in Multiphase Annular Brushless Exciters With Armature Winding Short-Circuit Faults

Precise measurement and analysis of the magnetic field play a crucial role in monitoring multiphase annular brushless exciters (MPABEs), especially in diagnosing armature winding short-circuit (AWSC) faults on the unmeasurable rotor. In this article, every aspect of the rotating magnetic field of MPABEs is accurately measured by using a search coil (SC), after which the effects of AWSC faults on spatiotemporal distribution of main magnetic field are fully analyzed. First, the spectral distribution of the magnetic field and the spatial harmonic characteristics are analyzed based on the winding coefficients under both normal operation and AWSC faults. Next, the time-varying behavior of the rotating magnetic field is investigated through the induced electromotive force (EMF) of the SC. Prototype simulations and experiments are then conducted to validate the theoretical analysis. Finally, a robust AWSC diagnosis method based on SC magnetic flux measurement is proposed. Experimental results from the prototype indicate that the proposed diagnostic technique can sensitively and reliably detect one-coil AWSC faults, even during the dynamic regulation of excitation voltage. These findings can serve as a reference for AWSC fault research in MPABEs.