Nowadays, energy shortages and environmental pollution have received a lot of attention, which makes the electrification of transportation systems an inevitable trend. As the core part of an electrical driving system, the electrical machine faces the extreme challenge of keeping high power density and high efficiency output under complex workin g conditions. The development and research of new soft magnetic materials has an important impact to solve the current bottleneck problems of electrical machines. In this paper, the variation trend of magnetic properties of ultra-thin grain-oriented silicon steel electrical steel (GOES) under thermal-mechanical-electric-magnetic fields is studied, and the possibility of its application in motors is explored. The magnetic properties of grain-oriented silicon steel samples under different conditions were measured by the Epstein frame method and self-built multi-physical field device. It is verified that the magnetic properties of grain-oriented silicon steel selected within 30° magnetization deviation angle are better than non-grain-oriented silicon steel. The magnetic properties of the same ultra-thin grain-oriented silicon steel as ordinary non-oriented silicon steel deteriorate with the increase in frequency. Different from conventional non-grain-oriented silicon steel, its magnetic properties will deteriorate with the increase in temperature. Under the stress of 30 Mpa, the magnetic properties of the grain-oriented silicon steel are the best; under the coupling of multiple physical fields, the change trend of magnetic properties of grain-oriented silicon steel is similar to that of single physical field, but the specific quantitative values are different. Furthermore, the application of grain-oriented silicon steel in interior permanent magnet synchronous motor (IPM) for electric vehicles is explored. Through a precise oriented silicon steel motor model, it is proved that the magnetic flux density of stator teeth increases by 2.2%, the electromagnetic torque of motor increases by 2.18%, and the peak efficiency increases by 1% after using grain-oriented silicon steel. In this paper, through the investigation of the characteristics of grain-oriented silicon steel, it is preliminarily verified that grain-oriented silicon steel has a great application prospect in the drive motor (IPM) of electric vehicles, and it is an effective means to break the bottleneck of current motor design.

In this paper, an iron loss model considering multiphysics fields is proposed and applied in a high-speed axial flux permanent magnet motor (HSAFPM). The investigated HSAFPMs are fabricated using winding cores of conventional silicon steel (CSS) with a thickness of 0.27 mm and ultra-thin silicon steel (UTSS) with a thickness of 0.05 mm, respectively. The wound technique makes axial flux motors easier to manufacture, but induces bending stresses. Therefore, the core loss of the motor is affected by the interaction of high frequency electromagnetic field, temperature and bending stress. The article analyses the difference of bending stress induced by silicon steel sheets with different thicknesses, and according to the operating conditions of the motor, the magnetic properties of silicon steel under the bending stress-temperature-electromagnetic multiphysics field coupling conditions are analyzed, and an iron loss model considering multiphysics fields is proposed. The validity of the proposed model is verified by experiments on silicon steel sheets with multiphysics fields, and the accuracy is improved compared with existing models. Finally, two motors with different core material thicknesses are fabricated and the proposed iron loss model is verified in the motor using the finite element method for more accurate calculation of motor iron loss.

Because the magnetic properties of an amorphous alloy (AA) obviously change with the change of temperature, a finite element simulation method for a motor, considering the effect of temperature, is proposed in this paper. In the early design stage of the high-speed permanent magnet synchronous motor (PMSM), the simulation of motor performance is mainly based on the magnetic performance test data at room temperature provided by the material’s manufacturer. However, the influence of the temperature rise during the actual operation of the motor will lead to large errors between the simulation results and the measured results. Therefore, it is of great practical significance to measure the magnetic properties of the AA at different temperatures and use them for simulation purposes. In this paper, the magnetization characteristics and iron loss characteristics of the AA and silicon steel (ST100) used for comparison are measured at different temperatures, and the iron loss separation of the two materials at different temperatures is completed, and the hysteresis loss coefficient and eddy current loss coefficient at different temperatures are obtained. On this basis, the performance simulation of a motor model is carried out. The more accurate simulation method proposed in this paper can provide a reference for the design of AA motors in industry.

High-silicon steel 10JNEX900 is often considered as a good core material for high-speed motors due to its low losses. However, cores are often operated under the multi-physics coupling (rotating and harmonic magnetic field, temperature, mechanical stress) resulting in variations in iron loss, which directly affects the modeling accuracy of the motor. In order to accurately predict the 10JNEX900 motor loss, this paper conducts iron loss tests under multi-physics coupling on two kinds of silicon steel materials, high silicon steel 10JNEX900 (6.5% Si) and conventional silicon steel ST100 (3.0% Si), and analyzed the differential change rule of 10JNEX900 loss. On this basis, the article proposes a model for calculating the iron loss of 10JNEX900 motor considering multi-physics coupling factors, and calculates the iron loss of silicon steel sheet. Meanwhile, the magnetic field, temperature field and stress field of the permanent magnet synchronous motor were calculated by the finite element method. The differences in motor performance before and after considering the multi-physics field factors are also compared. Finally, the motor prototype is fabricated and tested. The difference between the predicted and measured iron loss in the motor at no-load is lower than 10%.

High saturation flux density, high permeability and low specific core loss in the rolling direction (RD) are the characteristics of anisotropic soft magnetic materials. In order to meet the requirements of high torque density, high power density and high efficiency for the electric vehicle traction electric motor, the application of anisotropic silicon steel, i.e., grain oriented electrical steel (GOES) sheets in traction electric motor is investigated in this paper. Firstly, Ultra-thin anisotropic silicon steel sheets are selected based on the analysis of material properties and the reduction of eddy current losses in the core. Then, the performance of the tooth-yoke spliced PMSM, which is superior to the conventional non-grain-oriented electrical steel (NGOES) sheet PMSM in terms of torque and efficiency, is analyzed using the finite element method (FEM). And the design of experiment and analysis of the results proved that the circular splice pattern of the motor tooth was superior to the dovetail splice. Finally, a GOES PMSM is manufactured for verification. It is revealed that the measured current amplitude of the GOES PMSM is about 6.06% lower than that of the NGOES PMSM under the same geometric parameters and rated output torque. When the electric motor is operating, as the speed increases, the efficiency and torque of the GOES motor are higher than those of the NGOES PMSM throughout the motor's operating range.

Ultra-high-speed permanent magnet motors (UHSPPMs) are gradually increasing in the number of scenarios to realize energy saving and emission reduction due to their advantages such as high power density and fast response speed, and their accurate design and analysis are becoming more and more important. UHSPMMs need to consider the effects of multiple physical fields such as electromagnetism, force, and heat on their performance and structure due to their high rotational speed and small size. In this paper, firstly, the loss of each component of the motor is accurately calculated, and the distribution of the flow field and temperature field inside the motor is obtained by computational fluid dynamics (CFD) to determine the limiting working conditions of each component of the motor. Secondly, the mechanical stresses of the rotor are calculated at different limiting working conditions, especially the checking of the stresses of the permanent magnets and the sleeves when they are working at different temperature gradients, in order to improve the reliability of the ultra-high-speed rotor. Furthermore, the dynamics analysis is performed for the whole rotor system to ensure stable operation for a long time at the rated working conditions. Finally, the dynamics of the whole rotor system is analyzed to ensure that the ultra-high-speed permanent magnet rotor can operate stably for a long period of time at the rated operating conditions. Based on the theoretical calculations and analyses, a 25 kW, 95 krpm prototype was designed and fabricated, and relevant experimental studies were carried out. The correctness of the calculation of rotor mechanical properties under extreme working conditions (extreme speed and extreme temperature) is verified through tests, which achieved the target of design accuracy within 5%, and can provide great help to further improve the high-precision design of UHSPMMs.