Motor cores usually operate at high temperatures, and the temperature affects their magnetic properties. It has been shown that the iron loss of 3.5% silicon steel decreases with the increase of temperature, and a model of iron loss considering the effect of temperature is proposed1-2, but this model is not applicable to high silicon steel. It is reported that the iron loss of 6.5% silicon steel increases with the temperature3. Therefore, the study on the evolution of the temperature-dependent iron loss of silicon steel with different Si contents is particularly important, and there are few studies in this area.
In the second part of this paper, the magnetic properties of silicon steels with different Si contents (2.5%, 3.5%, 4.5%, 5.5%, 6.5%) were tested at variable temperatures (-70°C-200°C) using a self-built multi-physical field coupling test system and non-standard ring sample test method, as shown in Fig 1.Some of the experimental results are shown in Fig 2, which reveal variation of iron loss law of silicon steel with different Si content under the effect of temperature, and explain the reason of this phenomenon from the internal microstructure of the material. The third part of this paper uses the above experimental data to reconstruct the loss model for a 6.5% silicon steel. The correlation analysis of temperature effects on eddy current losses and hysteresis losses of high silicon steel is carried out respectively, and the temperature-dependent loss coefficients are added to the corresponding mathematical model. The fourth part of this paper compares the experimental test data of high silicon steel loss, the calculated data of traditional loss model and the calculated data of this loss model to analyze their error accuracy, and finally verifies that for the loss calculation of high silicon steel, the proposed iron loss model is more accurate than the traditional calculation model. Finally, this study will be of greater guidance for the design of subsequent high-silicon steel motors.
References:
1 J. Q. Chen, D. Wang, and S. W. Cheng,“Modeling of temperature effects on magnetic property of non-oriented silicon steel lamination,” vol.51, no.11, Nov. 1, 2015.
2 N. Takahashi, M. Morishita, D. Miyagi, “Examination of magnetic properties of magnetic materials at high temperature using a ring specimen,”,vol. 46, no. 2, pp. 548–551, Feb.2010.
3 Ou, J, Liu, Y, Breining, P, Experimental Characterization and Feasibility Study on High Mechanical Strength Electrical Steels for High-Speed Motors Application. 57(1), 284-293.

Fig.1 Multiphysics coupled magnetic performance testing system and test sample

Fig.2 (left) Iron loss curves at different temperatures. (right) Variation of iron loss with temperature