Post-assembly magnetization can significantly simplify the manufacturing of the rotor of permanent magnet (PM) electrical machines. The optimization of the post-assembly magnetizing device using finite element analysis (FEA) is time-consuming; therefore, a globally optimal solution aiming at achieving an adequate magnetizing level and minimal energy consumption is difficult to achieve. In this paper, a field–circuit coupling analysis (FCCA) model is proposed to optimize the auxiliary stator-type magnetizing device for interior permanent magnet synchronous machines (IPMSMs). A reasonable simplification of the highly saturated magnetic circuit is made based on FEA results so that the magnetic equivalent circuit (MEC) model can be established. On the other hand, the eddy currents in the PMs are equivalent to an eddy current short-circuit; thus, by converting the field calculation into a circuit calculation, the time cost can be reduced significantly, which greatly improves the speed of multi-objective optimization of the magnetizing device with multiple degrees of freedom. A V-type IPMSM is taken as a study case, and its post-assembly magnetizing device is optimized with the proposed method. FEA and experimental results show that the PMs are fully magnetized, while the required energy consumption is greatly reduced when compared with an existing magnetizing device.

Low-speed high-torque permanent magnet synchronous machines (PMSMs) are widely used in heavy industrial production, whereas the bulky prototype size poses challenges for assembly. This paper presents a 400kW low-speed high-torque spoke-type PMSM equipped with integrated magnetizing coils for post-assembly magnetization (PAM) to improve assembly performance. Magnetic equivalent circuit models show that the magnetization effect can be optimized by manipulating the eddy currents within machine components, without an influence on machine operation. An analytical model is then developed, accurately evaluating the eddy current effects from the perspective of effective magnetic permeability. To enhance the PAM effect, conventional aluminum alloy spacers are replaced by epoxy glass laminate spacers, and an aluminum alloy plate is introduced in the airgap above the PM to be magnetized. This method has a harmless impact on machine performance, including mechanical and thermal concerns. The finite element simulation validates that this method significantly improves the magnetization saturation state and evenness in the magnetized PM, enhances the consistency of all PMs in different positions, and mitigates the adverse effect on subsequently magnetized PMs in this step-by-step magnetization. The shielding effect of the aluminum alloy plate also protects the armature windings from high induced voltage during PAM. Finally, a prototype is fabricated, and the magnetization saturation state along with the surface flux density of post-assembly magnetized PMs are experimentally measured, validating the effectiveness of the proposed magnetization method.

Post-assembly magnetization (PAM) has become a widely adopted technique in the production of permanent magnet (PM) electrical machines, offering advantages such as simplified assembly processes and reduced manufacturing costs. However, for V-type interior PM synchronous machines (IPMSMs), magnetizing the bottom regions of V-shaped PMs deep inside the rotor close to the shaft presents significant challenges due to weaker magnetizing fields in these areas. Consequently, achieving full magnetization for the PMs often requires a substantial increase in the charging voltage. This paper investigates the influence of the shaft material on the PAM process, considering the effects of eddy currents within the shaft. The impact of the shaft's electrical conductivity and magnetic permeability on the magnetizing field strength is analyzed using the magnetic equivalent circuit (MEC) model and then verified with finite element analysis (FEA). The results suggest that a proper selection of shaft material can suppress eddy currents within the shaft, strengthen the magnetizing field in hard-to-magnetize PM regions, and reduce energy consumption during PAM. Experimental tests are carried out with shafts made of different materials and validate the effectiveness of the proposed approach.

Post-assembly magnetization (PAM) simplifies the fabrication of permanent magnet machines and pole-by-pole magnetization is adopted when employed in large-scale systems. However, this method inevitably generates stray fields through flux leakage across adjacent magnets, which induce undesired reverse magnetization and significantly increase the power required for subsequent magnetization. This paper proposes a staged PAM strategy with induction heating to reduce the required magnetizing field intensity for the reversely magnetized PMs, utilizing the temperature-dependent characteristics of the Nd-Fe-B magnets. The magnetizing coils are repurposed as induction heating coils using an AC power supply, allowing localized heating of affected PMs to lower their coercivity. An analytical model is developed to guide the selection of AC heating power supply specifications, balancing heating efficiency and duration. Finite element simulations are conducted to validate the loss predictions and evaluate the transient thermal behavior. Finally, experimental results from a 1/12-module of 400 kW 1.61 m outer-diameter prototype verify that full magnetization can be achieved with limited magnetizing current, demonstrating the method’s effectiveness for large-scale PM machine production.