Numerical Analysis of Reactive Power Distribution between Two Coupled Coils by Poynting Vector

This paper analyses the reactive power distribution of an inductive power transfer (IPT) system with two coupled coils based on the Poynting vector. The imaginary part of the complex Poynting vector is analyzed by the cross-product of the magnetic and electric field at an arbitrary point to represent the reactive power density. The system is modelled with a time-varying current flowing through the primary coil, and the reactive power distribution is analyzed under both no-load and loaded conditions. Based on general theoretical analysis, three-dimensional numerical analysis by Computer Simulation Technology (CST) software was conducted to show the reactive power density distribution. It has found that the imaginary components of the Poynting vectors concentrate around the primary coil when the secondary is open-circuited without active power flow. When the secondary is connected with a uniformly distributed resistive load, the results show that the imaginary parts of the Poynting vectors concentrate along with the primary and the secondary coil respectively. This work is useful for understanding how the reactive power distributes and circulates between the two coils of an IPT system.