Electrical equipment is tending to miniaturization and high frequency in modern industry development. High frequency transformer (HFT) has a broad application prospects whose volume obeys the law of inverse-squares of the operating frequency. Magnetic properties of its core materials under actual conditions need to be studied.
The soft magnetic ferrites, amorphous and nanocrystalline alloys are usually used to the core of HFT. High running frequency can also lead to the increase of power loss in the magnetic cores and windings, which will cause the temperature rise. Magnetic properties of the core materials measured in laboratory at room temperature cannot meet the requirement of performance analysis and loss evaluation of HFT. Therefore, it is necessary to do further research on the magnetic properties and loss properties of high frequency core materials at different temperatures.
In this paper, a testing system for ring sample is designed considering the influence of temperature. Magnetic properties of the ferrite (N87), nanocrystalline (1k107B) and amorphous alloys (1k101) are measured in the range of 25 °C to 120 °C from 1 kHz to 20 kHz. The saturation flux density, coercive force, remanence, permeability and loss properties of the above materials at different temperatures are analyzed and the change regularities are summarized. The temperature dependencies of three materials under different conditions are compared by using the coefficient of loss variation. At the specific flux density, the loss variation with temperature of 1k101 is the least, 1k107B is the slightly worse than 1k101, and the loss variation with temperature dependence of ferrite is the largest. With the increase of frequency, the loss variation of 1k107B with temperature decreases and their temperature stability is better than the other two materials. Meanwhile, the conductivity of material at different temperatures is measured and analyzed by using van der Pauw method. The overall performances of core materials are summarized in combination with the experimental phenomena and three materials are evaluated objectively.