This work presents the method of calculating the core loss in ferrite cores by using a
linear and sinusoidal finite element solver based on the material property data (the
complex permeability, the dielectric constant, and the AC conductivity) measured in the
laboratory. Due to the lack of published material data and fundamental test procedures,
this work also demonstrates the measurement techniques of material data which are
necessary for the finite element analysis (FEA) of the ferrite core loss.
First, a linear mathematical model of the ferrite core loss is formulated to characterize
the hysteresis loss and the eddy current loss. The magnetic properties (the real and the
imaginary components of the complex permeability) and the electric properties (the
dielectric constant and the conductivity) are required.
Second, the experimental procedures of those four properties are first presented.
Toroids with 1.1 OD/ID ratios are selected as samples to obtain the magnetic properties.
It is illustrated that the hysteresis loss should be measured at the frequency of interest,
instead of DC, due to its frequency-dependence. The electric property data of ferrites are
collected by using a disk sample which forms a capacitor. The conductivity tested is
frequency-dependent due to the combination of the dielectric loss and the DC conduction
loss.
Finally, core loss simulations for the sample toroid, an EE core, and an RMIO core
are performed and compared with the measurements. The flux and loss distributions are
demonstrated in the last two cores. The hot spots are identified from the field plots.
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