Abstract
The B-H loop of ferrite becomes narrower with a decrease in the excitation frequency. However, even at frequencies lower than 1 kHz, the B-H loop exhibits a certain minimum width, which is referred to as the (DC) hysteresis loop, and its area corresponds to the hysteresis loss. The dynamic magnetic loss is obtained by subtracting the hysteresis loss from the B-H loop area measured at a frequency above 1–10 kHz. The temperature characteristics of the hysteresis and dynamic magnetic losses are determined to be experimentally different, which suggests that the mechanism for the generation of dynamic magnetic loss is not exactly the same as that for the hysteresis loss. The dynamic magnetic loss is expressed using the dynamic magnetic loss parameter, which is a function of B and its time derivative, dB/dt. The dynamic magnetic loss parameter is measured under excitation with a rectangular waveform voltage. A ferrite core of TDK PC47 was used and the maximum magnetic flux density Bm, was set to 350 mT. The measured dynamic magnetic loss parameter was experimentally verified to be one of the intrinsic characteristics of ferrite and was also validated for cases of excitation with sinusoidal waveform voltages.
Highlights
The eddy current loss in ferrite is quite small due to the presence of highly resistive grain boundaries; ferrite cores are often used in high-frequency electric power converters, DC-DC converters, of which the switching frequencies are typically around 10 kHz to 1 MHz
The dynamic magnetic loss is obtained by subtracting the area associated with the hysteresis loss from the total loop area measured at a frequency above 10 kHz
The magnetic field intensity that constructs the B-H loop measured at frequencies higher than a few tens of kilo-hertz is divided into three components, which are related to the saturable magnetization curve, the hysteresis loss and the dynamic magnetic loss, respectively
Summary
The eddy current loss in ferrite is quite small due to the presence of highly resistive grain boundaries; ferrite cores are often used in high-frequency electric power converters, DC-DC converters, of which the switching frequencies are typically around 10 kHz to 1 MHz. The magnetic field intensity that constructs the B-H loop measured at frequencies higher than a few tens of kilo-hertz is divided into three components, which are related to the saturable magnetization curve, the hysteresis loss and the dynamic magnetic loss, respectively. These three components are analyzed separately and characterized using each of their related nonlinear parameters. The dynamic magnetic loss parameter is used to express the dynamic magnetic loss and its related magnetic field intensity
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