Saturated magnetization of permanent magnets depends on the intensity and direction of the applied pulsed magnetization field. Uneven distribution of magnetization field may results in local unsaturation, especially during the post-assembly magnetization process. Researchers have found that the saturated magnetization field intensity increases with the angle between the magnetization field and the easy axis of anisotropic permanent magnets. When the angle is equal to 90°, the saturated magnetization field tends to be infinite. This article studies the saturated magnetization characteristics of anisotropic NdFeB. The magnetization experiment platform which can adjust the direction of magnetization field is designed, and the saturated magnetization characteristic curves of sintered NdFeB magnet in fields of different intensity and angle are measured. The experimental results show that the saturated magnetization field intensity increases with the angle between the magnetization field and the easy axis, and when the angle is greater than 70°, magnetization field as high as 10 T cannot make the permanent magnet be saturated. The model of the saturated magnetization field along the easy axis and deviate from the easy axis are proposed based on intrinsic coercivity, demagnetization field, and an effective field coefficient, which fits the experiment results well. The saturation magnetization criterion of permanent magnetic material is proposed. Combined with the simulation of the intensity and direction of the pulsed magnetization field, we can judge the saturation region of permanent magnetic poles, thus helping us to design the post-assembly magnetization coils.

This paper presents the design and test results of a saddle-shaped post-assembly magnetization coil for a 2-pole high-speed permanent magnet (PM) rotor. The magnetization coil can gener-ate pulsed transverse magnetization fields of magnitude equal to 6 T/10 ms in a bore having a diameter of 85 mm and a length of 280 mm, thus meeting the needs of parallel magnetization of a 300 kW 2-pole high-speed PM rotor. The saddle-coil structure im-proves the coupling between the coil and the rotor, and its mag-netic energy reduces to 61% compared to the existing triple-coil structure. The influence of eddy current on the magnitude and direction of the magnetization field is analyzed and the pulse-width and coil supporting structure are optimized. The energy storage of capacitor bank pulse power supply is reduced to 230 kJ, which is 50% of the triple-coil structure's storage. The coil is fabricated and tested, and it is shown that it can successfully magnetize a 300 kW 2-pole high-speed PM rotor.

The aim of traditional designs of pulsed magnets is to keep the von-Mises stress on the midplane less than the ultimate tensile strength of materials. However, recently failed high-field experiments showed that some short circuits occurred at the magnet end, which is most possibly caused by the axial displacement of wires. This indicates that the former design is inadequate and accurate axial mechanical analysis of magnets is necessary. In this paper, a finite element model of pulsed magnets considering interface characteristics is proposed. Both the contact status and interfacial friction between the conductor layers and reinforcements can be accounted for Simulations are conducted with a failed 95 T dual-coil prototype, which was originally designed with the self-developed Pulsed Magnet Design Software (PMDS) software. The simulation results show that all the originally expected separations calculated by the PMDS software disappear due to the compression. This makes the calculated maximal von-Mises stress of the inner four reinforcement layers about 600 MPa less than the former designs. The influence of the interfacial friction is also presented. Besides, the simulations show that the maximum axial displacement at the magnet end is up to 8 mm at the designed peak field, which is deadly to the insulations. Hence, we suggest that the axial displacement at the magnet end should also be one design objective of pulsed magnets. At last, the factors affecting the axial displacement are analyzed.

A 25 kV/40 kA protection inductor with low stray field was designed and the first prototype was fabricated. The protection inductor protected the thyristor switch in the capacitor bank, limit the current at 40 kA in case of a short circuit. It was designed as a toroidal system consisting of 12 coils evenly distributed in the perimeter of a circle. The inductance could be changed easily by adjusting the number of coils. The structure of coils was optimized to withstand the great electromagnetic force produced by the 40 kA current. The coils were wound by a 4 45 mm copper strip standing on edge. Each coil was externally reinforced by a stainless steel ring tightly enclosing the coil. The first prototype was fabricated. Its inductance and magnetic field were tested. The prototype has been mounted in the 1 MJ module and is now in operation. In this paper, the structure design, fabrication and testing of a new protection inductor are presented. The testing results are discussed. Tested inductance was 1.05 mH and direct resistance was 16 . The first prototype was proved to be successful and 13 more protection inductors will be made after some improvements.

It is well-known that post-assembly magnetization could simplify the manufacturing process and enhance the performance of interior permanent-magnet motor (IPM). However, due to the complexity of magnetic circuit structures of IPMs, this technique is hard to achieve because of difficulties in generating an appropriate magnetization field and developing high-strength coils. Consequently, the majority of existing researches still stay in simulation stage with low-power motors. In this research background, this paper mainly focuses on studying post-assembly magnetization of a high-power IPM. Based on a magnetic characteristics test of N42UH Nd–Fe–B permanent magnet material, the paper researches impact of skewed rotor, electromagnetic design and structure design of coils. Finally, a post-assembly magnetization system for 160 kW IPM is created to demonstrate the effectiveness of this system.