Development of New Powder Magnetic Core Technology to Achieve Miniaturization and High Performance of Reactors for Electric Vehicles

Abstract

We have developed Fe-Si-Al powder with Al₂O₃ insulating film and a new powder magnetic core made by compression molding and annealing this powder for reactors used in electric vehicles. This magnetic core achieves the targeted linear magnetization curve by utilizing the Al₂O₃ insulation film on the surface of the powder particles, which performs the function of magnetic resistance previously provided by gap spacers in the conventional reactor. As a result, we have achieved a 30% reduction in size for miniaturization compared to conventional reactors, a 25% reduction in core loss for lower power loss compared to the conventional model, and a reduction in the number of components. The raw material Fe-Si-Al powder was manufactured adopting gas atomization technology to achieve spheroidization and component control. The Al₂O₃ insulating film was uniformly deposited with a consistent thickness using a novel method based on a metal vapor phase reaction process. Furthermore, the strength of the core was significantly improved, which was achieved by mixing a small amount of glass powder and compression molding the core, then melting and hardening the glass during annealing. This product has been adopted in vehicles released on the market in 2022.