Quasi-3-D Hybrid Analytical Method of Open-Circuit Stray Magnetic Field Considering Unsaturated Magnetic Permeability and End Leakage Flux

Motor fault diagnosis based on stray magnetic field (SMF) has broad prospects due to its noninvasive advantages. Rapid and accurate acquisition of SMF is crucial for fault diagnosis and mechanism analysis. However, unsaturated magnetic permeability of the iron core and end leakage flux are ignored in existing analytical models (AMs) of SMF, resulting in the inability to accurately calculate the three-dimensional (3-D) distribution of SMF. Motivated by this, this article proposes a quasi-3-D hybrid analytical method (HAM) of open-circuit stray magnetic field of external rotor permanent magnet motor (ERPMM). First, a quasi-3-D equivalent magnetic circuit model is established to calculate the air-gap magnetic field and end leakage flux at different axial positions. Second, the EMC models and iterative convergence algorithm are synergistically integrated to predict the unsaturated magnetic permeability at different axial positions of the rotor. Finally, a quasi-3-D virtual equivalent subdomain model is developed to calculate the 3-D distribution of SMF. The accuracy and efficiency of the proposed quasi-3-D HAM are verified through experiment and finite element model, respectively. This article provides a new approach for the analytical modeling of SMF of ERPMM.