A Fast 3D Numerical Impedance Calculation for Litz Wire and Air-Core Coils

This paper presents a 3D numerical impedance calculation method based on cylindrical elements. It can be used to model the Litz wire and further air-core coil wound by the Litz wire. The discretization is based on cylindrical elements, resulting in a small amount of elements. Cylindrical element analysis is based on a 2D analysis and its analogue to 3D. The analysis considers both transverse and longitudinal magnetic fields applied to elements. The proposed method is applied to several Litz wires and compared with 3D FEM, which validates the method has good accuracy and fast computational speed. The effectiveness of the method for the air-core coil is validated by measurements. The proposed method is promising in facilitating coil optimization.