Design Principles for Maximization of an Inductive Power Transfer System Inherent Tolerance to the Coils Misalignment

Abstract

This paper presents an analysis of the inductive power transfer system (IPT) in terms of its tolerance to the coils misalignment. We introduce two new metrics, which we refer to as misalignment tolerance (MT) and $\alpha $ , for formal assessment of the IPT system tolerance to the misalignment. Using these metrics, we evaluate two common design scenarios: an IPT system with maximized power transfer efficiency (PTE) and an IPT system with maximized power delivered to the load (PDL). Based on this analysis, we formulate design principles aimed at maximizing the inherent tolerance of the IPT system to the coils misalignment, i.e. the tolerance that is achieved before adding control loops in the IPT system. The presented principles cover both the system level, where the coils geometry is fixed, and the coil couple level, where the coils geometry is optimized. We derive an analytical equation for the calculation of the optimal critical coupling, which leads to the maximization of MT. We also present an exemplary coils optimization procedure for the improvement of MT. The procedure demonstrates that an IPT system with an asymmetrical number of turns achieves higher MT. To validate our findings, four IPT system prototypes with different values of critical coupling, as well as optimized and non-optimized coils were manufactured and compared. The IPT systems with non-optimized and optimized coils exhibited MT of 73% and 82%, correspondingly.

Keywords

• Coils displacement
• coils misalignment
• critical coupling
• inductive power transfer
• wireless power transfer