Current Loop Approach to Computing Losses in Coaxial Multi-phase Air-core Coil Systems

This work presents a procedural method for analytically computing losses in solid conductor air-core coils. The approach was developed for the coaxial subset of air-core coil systems in which hoop-turn, axisymmetric assumptions can be made. It encapsulates loss generally associated with magnetic diffusion, including that induced by rotating magnetic fields from multi-phase current sources, without computing the complex eddy current distribution in a conductor cross-section. Each turn in the system is replaced with an infinitesimally thin circular current loop and is independently excited according to a peak current and phase. Field contributions are summed up at each loop center, with the inclusion of phase to calculate the major and minor components of the resultant magnetic field at each turn. Well established analytic formulae are then used to compute loss accordingly. The approach is significantly faster than 2D axisymmetric finite element analysis (FEA) and greatly improves approximations for losses in isolated coils.