An Improved Mutual Inductance Electromagnetic Model for Inductive Power Transfer Systems Under Misalignment Conditions

One of the most challenging components of an inductive power transfer system to be designed is the coil set (transmitter and receiver coils). Due to the great number of variables, finite element software is frequently used in the simulation of the electromagnetic quantities of coil sets. These simulations take a long time to produce results. To shorten the time it takes to design a coil set, different electromagnetic models have been published. However, the published models are still dependant on extensive equations that require several numerical loops to be solved, or are not completely validated. In this paper, a new compact electromagnetic model is proposed. The proposed model uses quadrupole superposition to predict the magnetic field, induced voltage, and inductances of a coil set through a cubic polynomial function, whose coefficients are based on the parameters of the coil set. With the proposed model, it is possible to compute the mutual inductance of multiple coil sets for different horizontal misalignment conditions, after simulating (or measuring) the open-circuit voltage of only one coil set at zero misalignment. Thus, the proposed model helps greatly for coil topology analysis and design. The proposed model is validated through seven different experimental set ups featuring different coil sets, including receivers and transmitters formed by multiple quadrupoles, a transmitter formed by one main quadrupole and a resonant booster, and coil sets working at 5 kHz and 85 kHz. The experimental results show an excellent agreement with the proposed model.