A Fast Method to Optimize Efficiency and Stray Magnetic Field for Inductive-Power-Transfer Coils Using Lumped-Loops Model

Both the efficiency and stray magnetic field in inductive power transfer are influenced by the design of transmitter and receiver coils. Their synergetic optimization is realized with Pareto front. The conventional method to derive the front requires thousands of finite-element simulations to sweep the physical parameters of the coils, which is time consuming especially for three-dimensional simulations. This paper demonstrates a fast method to optimize the efficiency and stray magnetic field. The windings are replaced by several lumped loops. As long as the number of turns for each loop is known, the efficiency and magnetic field are calculated using permeance matrices and current-to-field matrices. Therefore, sweeping physical parameters in simulation is replaced by sweeping turns numbers of the lumped loops in calculation. Only tens of simulations are required during the entire procedure, which are used to derive the matrices. The Pareto fronts calculated using the lumped-loops model match well with those derived from simulation using parametric sweep. An optimal design selected along the Pareto front was fabricated and measured to verify the calculation accuracy. The verification shows the same efficiency and less than 12.5% difference of the stray magnetic field, for the results from calculation, simulation, and measurement.