Numerical and Experimental Characterization of Thread-Type Magnetic Core With Low Eddy Current Loss

This paper proposes a thread-type magnetic core as a new structured magnetic core made of iron threads and a surrounding insulator. The thread-type core has the advantages of lower eddy current loss, simple production, and low cost. The eddy current loss of the thread-type core is compared with that of bulk- and lamination-type cores. The losses are numerically analyzed using the finite-element method and are measured with an experimental test. The effect of eddy current on copper loss is also addressed. The numerical and experimental results show the usefulness of the thread-type core. Further numerical results show the size effect of the thread core, whereby the smaller size thread results in less eddy current loss.

I. Introduction

Iron loss is one of the significant points that must be taken into account when designing electric power machines. The iron loss depends on the material properties of the iron: conductivity, permeability, and hysteresis loop. Most of the magnetic cores for electric machines consist of an electrical steel sheet that has low eddy current loss since it is manufactured by mixing ferromagnetic material with high-resistive impurities and by laminating the steel sheet to block the passage for eddy current [1]. Nevertheless, other new magnetic materials are still under development for higher efficiency and performance. The permalloy and the nanocrystalline alloy powder are good examples [2]–[4]. However, their raw materials are expensive and their production requires complicated and costly processes. Therefore, their application is limited to some special devices. For example, in designing a new composite magnetic material that is composed of more than two different materials, the development process requires a significant amount of time and labor because its geometrical structure could vary and the composition ratio of different materials could be diverse.