High $Q$ Coil Measurement for Inductive Power Transfer

A system for the measurement of quality factors, self-inductances, and interturn capacitances of inductive power transfer coils, in the frequency range of 1-20 MHz, is demonstrated. Coil quality factor in excess of 1000 is measured at megahertz frequencies, beyond the capabilities of commercial impedance analyzers. The method used is to measure the transmission bandwidth of the coil under test while under weak magnetic coupling, incorporating measures to reduce common-mode coupling. The measurement system is verified by comparison with electromagnetic simulation and by modeling. The system model shows robustness to system configuration and the potential to measure coils with Q in excess of 10 000.