A Comparative Study on Parasitic Capacitance in Inductors With Series or Parallel Windings

In high-power medium-voltage applications, inductors usually have multiple windings on a single core, due to the high inductance value and high current stress. The multiple coils are electronically connected in either series or parallel, with considerations of windings loss and cost. However, the differences in parasitic capacitance of inductors using parallel and series connections are not discussed. Therefore, this article reveals that in comparison to parallel connections for windings, utilizing series connection for winding can significantly reduce the parasitic capacitance in multiwindings inductors without sacrificing the power density and adding manufacturing complexities. Physics-based models of parasitic capacitance in inductors with round-cable and copper-foil windings are developed for theoretical analysis. According to the theoretical analysis, the equivalent capacitance contributed by the stored electric field energy between two layers can be halved at least. The theoretical analysis is also verified by FEM simulations. Six prototyped inductors are experimentally compared to validate the theory.