Analytical determination of the first resonant frequency of differential mode chokes by detailed analysis of parasitic capacitances

Abstract

AcknowledgmentsThe authors would like to thank ABB Switzerland corporate research center in Baden/Daettwill for initiating and supporting this work. AbstractIn this paper the important parasitic capacitances of chokes are analyzed and defined. This work contributes to a general understanding of capacitive coupling in wound elements. Based on calculations from previous studies a more precise, wide range algorithm is proposed to calculate these parasitic capacitances of toroidal chokes. With these results a method is presented to analytically predict the first resonant frequency of a differential mode choke with high precision. Furthermore, the retrieved capacitance network offers the possibility to forecast resonant frequencies of higher order with high accuracy avoiding the need of measurement or field simulation.

Modeling and Minimization of the Parasitic Capacitances of Single-Layer Toroidal Inductors

“…Nevertheless it is generally not accurate enough for loose winding made with round conductors. In the literature this problem is solved with image theory [18], equivalent segment or arc parasitic capacitances [19]- [22], a combination of the two previous methods [23], conformal transform [24], or 2D FEM [25], [26]. The latter approach will be used in this paper because it takes into account insulation layers, coating, inter-turn and turn-core spaces.…”

“…In addition to the modelling of the EPC, some articles propose ways to reduce it. The authors of [23] have identified the turn-core capacitance as the most important one in the total EPC, and its dependence with the inter-turns space. Therefore they suggest to keep the winding tight to avoid the increase of the parasitic capacitive coupling between turns and core, and thus to reduce the EPC, (this has been confirmed in [18], [25], [26]).…”

Winding Optimization for Reducing Parasitic Capacitances of Common-Mode Chokes

“…For single-layer windings on high-permittivity materials, the coupling C tc could also be a dominant effect over C tt in determining the total electrical coupling between windings [13], [14]. Since C tc tends to increase for loose windings [10], this winding strategy increases the EPC of inductors with high-permittivity cores [14]. However, the situation is different if the core material does not have such a high permittivity, as is the case with NiZn ferrites [13].…”

“…Due to the problem posed by parasitic capacitances in inductive filtering components, various works in the literature focus on estimating the equivalent parasitic capacitance (EPC) for inductors or for specific connections of a CMC [5], [8], [9], [10], [11]. These studies demonstrate that EPC generally has a contribution arising from the electrical coupling between turns of the inductor and another contribution associated with the coupling of turns to the core.…”

Reduction of oscillations in a GaN bridge leg using active gate driving with sub-ns resolution, arbitrary gate-resistance patterns

“…2 with a highself-resonant frequency. However, core geometries are restricted ( [16], [17]) and windings costs may be increased. Alternatively, a second choke may be added in series with that in Fig.…”