Magnetic Equivalent Circuit Based Analytical Modelling of Interior Permanent Magnet Motor: A Critical Review

Interior permanent magnet (IPM) motors are widely used in electric vehicles and other emerging sectors for their high torque density, efficiency, and wide speed range. Accurate yet rapid electromagnetic performance prediction is essential for their preliminary design. While finite element analysis (FEA) offers high accuracy, its high computational cost limits early-stage design and large-scale topology screening. This review focuses on magnetic equivalent circuit based analytical methods - including lumped magnetic equivalent circuit (LMEC), general magnetic equivalent circuit (MEC), and reluctance network (RN) - and hybrid approaches that combine magnetic equivalent circuit with subdomain models (SDM), winding functions (WF), and conformal mapping (CM). magnetic equivalent circuit models represent the motor as a circuit of magnetomotive force sources and reluctances, enabling fast estimation of flux density, flux linkage, back-EMF, torque, cogging torque, and inductance across rotor topologies such as V-type, U-type, spoke-type, flat-type, delta, and multilayer designs. The impact of segmentation, nonlinear saturation handling, and topology adaptability on model accuracy, calculation time, and generality is critically compared. Hybrid models address magnetic equivalent circuit limitations in airgap and stator modelling, reluctance count, and rotor generality, with each category evaluated by achievable KPIs, load-condition adaptability, and calculation efficiency. The reviewed studies are systematically classified by modelling strategy and target calculation objects to help match analytical methods with specific design objectives. The paper concludes with future directions for developing generalisable hybrid frameworks, automated saturation modelling, and integration with multiphysics analysis to accelerate accurate and comprehensive IPM motor design.