On the assessment of an optimized method to determine the number of turns and the air gap length in ferrite-core low-frequency-current biased inductors

Abstract: This paper presents a first assessment of a design method aiming at the minimization of the number of turns $N$ and the air gap length $g$ in ferrite-core based low-frequency-current biased AC filter inductors. Several design cases are carried on a specific model of Power Module (PM) core, made of distinct ferrite materials and having different kinds of air gap arrangements The correspondingly obtained design results are firstly compared with the classic approach by linearization of the magnetic curve to calculate $N$ and the use of a fringing factor to determine $g$. Next, a refined design approach of specifying the inductance roll-off at the peak current and its potential limitations are discussed with respect to our design method. Finally, the behaviour of inductors operated beyond their design specifications is analyzed.