Determining the Optimal Range of Coupling Coefficient to Suppress Decline in WPTS Efficiency Due to Increased Resistance With Temperature Rise

The continuous operation of the wireless power transfer system (WPTS) under high-frequency switching activity might cause a temperature rise in various system's components. That temperature rise might increase the resistance of the primary and secondary coils, which will lead to a significant decline in the system's efficiency. To address this problem at the design stage, we investigate the optimal range of the coupling coefficient that suppresses the efficiency drop due to the increasing resistance of the WPTS components. The proposed optimal range of the coupling coefficient can also ensure the output power requirements of the WPTS. Using four different WPTSs, the determination method for the optimal range of coupling coefficients under different system operational frequencies was developed and implemented. A 3-kW resonant experimental prototype WPTS was designed and built to validate the proposed coupling coefficients experimentally. The experimental results show that the optimized coupling range successfully suppressed the efficiency decline resulting from the increasing resistance caused by temperature rise.