Using Powder Materials to Replace Air-Gaps for Fringing Flux Reduction

Amorphous or nanocrystalline gapped cores as well as powder cores are both popular in industrial power choke design. Both show different advantages and drawbacks, depending on their function within a circuit. In this paper we present a design-approach, combining both core-materials for choke design. The drawbacks of air gapped solutions are shown and compared to a solution, where the air gap is replaced by a distributed gap using a piece of powder material. We illustrate the much higher fringing flux of an air gapped structure and related losses. The design procedure of an inductor using a powdered material instead of an air-gap and the different saturation behavior of both solutions are shown.