Evaluating the practical magnetic properties of permanent magnets in multi-source magnetic devices via cross-scale micromagnetic simulation method

In multi-source magnetic devices (MSMDs), the magnetization states of permanent magnets (PMs) are affected by the superimposed magnetic fields generated by surrounding PMs, making the accurate evaluation and selection of their practical magnetic properties highly challenging. This interference is particularly pronounced in complex magnetic systems such as Halbach arrays, where conventional nonlinear magnetization models often produce distorted or unreliable results. To address this issue, we propose a cross-scale numerical method based on magnetic moment dynamics to assess the practical magnetic performance of PMs within MSMDs. This method establishes a reference framework for applying micromagnetic simulations to the magnetic performance evaluation of macroscale, device-level permanent magnets. An intrinsic magnetization model is developed by coupling the Maxwell and Landau–Lifshitz–Gilbert (LLG) equations with thermomagnetic interactions. The coercivity and dominant magnetization reversal mechanisms (nucleation and pinning) are calibrated using a 3D Voronoi-based polycrystalline parameterization. A cross-scale simulation framework is constructed by scaling the effective dimensions of the main magnetic phase through spatially distributed damping correction coefficients. With strong agreement between micromagnetic simulations and experimental demagnetization curves, the equivalent remanence and demagnetization rates of various sintered NdFeB magnets are evaluated at different positions within existing Halbach-type permanent magnet excited coaxial drives (PMECDs) and permanent magnet synchronous machines (PMSMs). Key findings include field attenuation caused by local magnetization reversal and multi-domain formation due to self-demagnetization in Halbach arrays. The proposed method offers a reliable reference for magnetic performance assessment and pre-design optimization of PMs in MSMD applications.