High-frequency transformer operates under high temperature and non-sinusoidal excitation. The magnetic properties and loss of soft magnetic materials under these conditions are complicated, which are quite different from those under normal temperature and sinusoidal excitation1-2. At present, most of the relevant researches separate the temperature dependence of magnetic properties from non-sinusoidal excitation, which not sufficient to characterize the magnetic properties of soft magnetic materials3-4.
This paper carried out magnetic property measurement and analysis under various temperatures (25~120°C) of high-frequency magnetic materials ferrite (N87) and nanocrystalline (FT-3KL) with multi-frequency (1~20kHz), different non-sinusoidal waveform excitation (square and rectangular wave), and multiple excitation states (Duty ratio 0.1~0.9). As shown in Fig.1(a), the temperature dependence of ferrite is significant, and its loss is less affected by the excitation state, while nanocrystalline is more sensitive to the excitation waveform. As shown in fig.1(b), the loss of nanocrystalline appears to be a minimal when the duty ratio is 0.5 and exhibits a symmetrical distribution.
As shown in Fig.2, Based on experimental data, we consider the effect of temperature in the modeling of loss prediction and improve the model which based on the Steinmetz formula. By comparing the measured results and the predicted values, the accuracy of the new loss model is within 15%, which is greatly improved compared to other existing loss models under the influence of temperature.
This work can provide a theoretical basis for the micro-magnetization mechanism of magnetic materials under complex operating conditions. The complete analysis of the magnetic properties and new loss model of the above materials will be shown in the full-text version.
References:
1 J. Chen, D. Wang and Y. Jiang, IEEE Transactions on Magnetics, vol. 54, no. 11, pp. 1-7, Nov. 2018
2 S. Li, B. Sarlioglu and S. Jurkovic, IEEE Transactions on Industry Applications, vol. 53, no. 5, pp. 4923-4933, Sept.-Oct. 2017
3 Shaoshen Xue et al., IET Science, Measurement & Technology, 2016, 10(8) : 846-854.
4 S. Barg, K. Ammous and H. Mejbri, IEEE Transactions on Power Electronics, vol. 32, no. 3, pp. 2146-2154, March 2017**

Fig. 1 (a) Duty ratio and loss curve of N87 excited by 20KHz square wave, B=0.15T (b) Duty ratio and loss curve of FT-3Kl excited by 20KHz square wave, B=0.9T

Fig. 2 Comparison of N87 loss prediction and measurement results