Researchers Zhao Guoxin and Kong Decai from the School of Electrical Engineering at Shenyang University of Technology pointed out in an article published in the 2018 issue of the Journal of Electrical Engineering that soft magnetic composite materials are made by pressing metal powder particles with insulating surfaces. They have the characteristics of low eddy current loss and isotropy and have been applied to some extent in recent years. However, they have high hysteresis loss and low permeability, so their applicable occasions and specific differences from silicon steel sheets need further in-depth research.
This paper first uses the ring sample method to test the magnetic properties of soft magnetic composite materials, obtaining their no-load magnetization curves and loss data at different frequencies. Then, to compare and analyze the differences between soft magnetic composite materials and silicon steel sheets in motor applications, two permanent magnet synchronous motors were designed using soft magnetic composite materials and silicon steel sheets respectively. The magnetic field, iron loss, and the variation of iron loss at different frequencies of the two types of motors were analyzed and calculated. Finally, prototype testing was conducted to understand the differences in the application of the two materials in permanent magnet motors, verify the accuracy of the calculations, and summarize the application range of soft magnetic composite materials.
Soft magnetic composite materials (SMC) are obtained by molding pre-mixed high-purity iron powder with an insulating layer and organic materials using powder metallurgy technology. In recent years, they have been widely studied and applied in fields such as motors [1-4]. The ability of SMC materials to be directly molded makes motor structures and electromagnetic designs more flexible, diverse, and innovative, opening up new directions for the application and development of motors and attracting a large number of researchers [5-7].
SMC material's high resistivity and low eddy current loss make it more suitable for use in high-frequency motors. However, SMC material also has some unavoidable drawbacks, such as low permeability and high hysteresis loss. Therefore, the application patterns and characteristics of SMC material in motors still require further in-depth research.
Reference [7] conducted a thorough study on SMC material motors and found that the motor performance of SMC and silicon steel sheet motors differed at different speeds and output powers. The SMC material motor had low efficiency at 1000 r/min and 625 r/min, and its efficiency was 28% and 34.7% lower than that of the silicon steel sheet motor at a motor current of 4A. At speeds above 1500 r/min, the SMC material motor had high efficiency, which was 3% higher than that of the silicon steel sheet motor.
Reference [8] also compared the efficiency of induction motors made of SMC material and silicon steel sheet material. It found that with the same power supply voltage, the efficiency of SMC material motor was 7% lower. However, SMC motor is more sensitive to power supply voltage. After reducing the power supply voltage, the efficiency of SMC motor can be improved. When the power supply voltage was reduced from 220V to 180V, the efficiency increased by 4.7%. However, the overall efficiency of SMC motor was lower than that of silicon steel sheet motor. When the power supply voltage was 220V and 180V, it was 10.3% and 6.7% lower, respectively.
Although SMC materials have a certain research and application foundation, the characteristics, occasions, and rules of their application in motors, as well as the differences in properties between SMC and silicon steel sheets at different operating frequencies, still need to be studied.
To study the properties of SMC material and analyze its differences from traditional silicon steel sheets, this paper first tests the magnetic properties of SMC material (Somaloy 700) produced by Hoganas and compares it with commonly used 0.5mm thick silicon steel sheet DW470. Then, two permanent magnet synchronous motors with the same size and parameters are designed using SMC material and DW470 as the core material, respectively. Magnetic field analysis and loss calculation are performed on the two motors to analyze the characteristics and differences between the prototypes made of the two materials. Finally, prototypes are manufactured and tested to determine the performance differences between the two prototypes.
Through analysis and comparison, this article summarizes the characteristics of SMC materials, reveals the differences in motor performance between SMC and silicon steel sheets, and outlines the applicable scenarios for SMC materials. This allows us to summarize certain patterns for the application of SMC materials in motors .
in conclusion
To compare the performance differences between silicon steel sheets and soft magnetic composite materials in motor applications, this paper designed and manufactured two permanent magnet synchronous motors with SMC and DW470 cores, respectively. Based on finite element analysis and experimental research, the following conclusions were drawn:
1) The magnetic properties of SMC material were tested using the ring sample method, and the magnetization curve and loss curve of SMC material were obtained. By comparison with DW470, it was found that the magnetic permeability of SMC material is relatively low. The specific loss of both materials increases with the increase of frequency. 400Hz is a key frequency point. Below 400Hz, the loss of silicon steel sheet material is less than that of SMC material. When the frequency is higher than 400Hz, the specific loss of soft magnetic composite material is lower than that of DW470 material.
2) According to the no-load test, the back electromotive force of the SMC prototype is smaller than that of the DW470 motor, which is consistent with the theoretical calculation and verifies the low permeability of the SMC material. Load tests were conducted on both prototypes. The results show that the DW470 motor has higher efficiency at frequencies below 400Hz. However, as the frequency increases, the efficiency difference between the two materials decreases. At 400Hz, the frequencies of the two are basically the same, which is consistent with the theoretical calculations. This indicates that the SMC permanent magnet synchronous motor has excellent performance at medium and high frequencies, which can compensate for the disadvantages of low permeability and high hysteresis loss, and has good application prospects.
3) Because SMC material is fragile, the thickness should be increased appropriately during the design process, and sharp edges should be avoided as much as possible. After processing, glue or epoxy resin should be applied to increase the strength of the core and prevent "slag shedding".
