Design Considerations for Enhanced Coupling Coefficient and Misalignment tolerance Using Asymmetrical Circular Coils for WPT System

Abstract

In case of misalignment, variation in the coupling coefficient between transmitting and receiving coils employed for wireless power transfer is obvious. During the design process of coil system, assurance of least affected coupling coefficient during misalignment is an important issue and can be addressed through appropriate coil structure. Asymmetrical circular spiral coils with unequal outer diameter and fixed self-inductance exhibits better tolerance to misalignment with the limitation of smaller averaged coupling coefficient. The present paper considers the analytical model of asymmetrical circular spiral coils to investigate the dependency of the coil system dimensions on mutual inductance and coupling coefficient with equal outer diameter. Based on the observations from analytical expressions, simulations are performed through finite element method approach using ANSYS MAXWELL. Outcome of the investigations has been used for the design consideration of coil system, which is less sensitive to the misalignment. Based on the proposed design considerations, experimental setup is developed and tested for the case study of E-Rickshaw with 400 mm outer diameter and 120-mm air gap.