High-Precision Nonlinear Semi-Analytical Model of High Torque Density 3-D Magnetic Circuit Permanent Magnet Motor in Aircraft Electric Propulsion Application

This article proposes a novel high-precision nonlinear semi-analytical model for the magnetic fields and the electromagnetic performance calculation of 3-D magnetic circuit permanent magnet motor (3DMCPMM) in aircraft electric propulsion applications, which can take the effects of the magnetic saturation nonlinearity and the permanent magnet (PM) end-leakage flux into account. The high torque density 3DMCPMM topology is first proposed, which can improve the output torque per unit weight via the 3-D magnetic circuit coupling. To simplify the computation, the 3-D magnetic circuit equivalent decoupling method is proposed for 3DMCPMM, which can convert the 3-D magnetic circuit into dual 2-D magnetic circuits. The 3DMCPMM analytic model is then proposed based on the harmonic subdomain approach, which can accurately predict the magnetic field distribution and the electromagnetic performance. Furthermore, using the equivalent magnetic circuit (EMC) model, the PM end leakage flux coefficient is proposed for the 3DMCPMM analytic model, which can eliminate the calculation error due to the PM end-leakage flux effect. The nonlinear iteration-based magnetic permeability is proposed for the 3DMCPMM analytic model, which can improve the analytic calculation accuracy by considering the magnetic saturation nonlinearity. A 630-N·m 3DMCPMM is designed and manufactured with the torque density of 25.37 N·m/kg. Simulation and experimental results show that the proposed semi-analytic model has an excellent electromagnetic prediction performance with a maximum calculation error of 4.62%, which can achieve the analytic calculation of 3-D magnetic circuit motor. The 3DMCPMM semi-analytical model is proposed for the first time, which lays the foundation for the 3DMCPMM rapid design and iterative optimization.