A Calculation Method on High-Frequency Loss of Double-Layer Composite Conductor

In order to reduce resistance loss due to skin effect and proximity effect in high-frequency inductive wireless transmission coils, an impedance calculation model is built in this paper for analyzing the electromagnetic field and resistance loss of the double-layer composite conductor in the frequency range of less than 100 kHz. The analytical formulas on calculating high-frequency resistance and power loss of the composite conductor are obtained. It is found that there is a critical frequency above which the resistance of the double-layer composite conductor is significantly lower than that of a pure copper conductor. The loss density within the aluminum layer is lower than that of a copper conductor, and will increase sharply at the interface between copper and aluminum layer. The wiring mode, coil shape factor, and the magnetic field angle determine the distribution of the magnetic field intensity around the composite conductor. When the angle of magnetic field vector varies from 0° to 360°, the magnetic field intensity will vary in a spiraling way. Finally, the high-frequency resistances of the two double-layer composite conductor coils are measured and are consistent with the analytical results, which is helpful to the high-frequency coil design in inductive wireless power transmission.