The frequency characteristics of an inductor are mainly affected by three factors. A. The influence of core material loss is the most important, which causes the Q value to exhibit a negative slope from the maximum value. B. Dielectric loss is also an influencing factor, especially in high frequency bands. C. The third influencing factor is the self-resonance effect of distributed capacitance and inductance.
The performance of the inductor is negatively affected by the self-resonant frequency, which is determined by the distributed capacitance and self-inductance, which is determined by the winding method. Minimizing distributed capacitance is a very important consideration in wirewound design. For the winding of the toroidal magnetic powder core, its effective capacitance is in parallel with the inductance, and this distributed capacitance is the sum of the capacitances between the wires, between the layers, and between the winding itself and the magnetic powder core.