Loss Analysis of Magnetic Core and Its Structure Optimization of Magnetic Coupling Structure in Wireless Power Transfer System

Abstract

Wireless power transfer (WPT) technology has been widely studied and used in academia and industry. However, the system's efficiency is still the bottleneck of WPT technology. Moreover, the magnetic coupling system's loss usually occupies much of the total loss. Furthermore, the magnetic coupling system's core loss is hard to model and optimize due to the uneven flux density distribution in the magnetic core. Therefore, this paper analyzes the magnetic flux density inside the magnetic coupling system's magnetic core with a spiral winding structure. It reveals that the flux density is quite uneven in the magnetic core, and the core loss dominates where the flux density peaks. Based on it, a new varied section of the magnetic core structure is proposed. An approximate even flux density distribution can be obtained with the proposed structure, and 37.14% can greatly reduce the core loss. Considering the proposed method's manufacturing difficulty, a double-section improvement method of the magnetic core structure is proposed. With the double-section improvement method, the flux density can be evener compared to the traditional unique section method. The core loss can be effectively reduced. Finally, a 3kW electric vehicle's WPT system is taken for experiments. The double-section method can improve the total efficiency by 0.8%, the machine maximum efficiency reaches 95.3%. It verifies the proposed method to be correct and useful.