Design and Analysis of a Novel CPT System with Soft Ferromagnetic Material Cores and Electromagnetic Resonant Coupling for Evs

Abstract

This paper describes a novel contactless power transfer (CPT) system with geometrically improved H-shape ferromagnetic cores and electromagnetically prospective modelling analysis methods for wireless power transmitting (WPT) applications of electric vehicles (EVs). A CPT prototype, using optimized H-shaped magnetic couplers and series-to-series (SS) compensation, is proposed to address and ensure the maximization of system efficiency, power transfer ratings, and air gaps of coupling coils. By focusing on the main factors such as various system operating frequencies, different geometric designs of coils, changeable inductive coupling distances, electromagnetic field performances and actual phase angle deviations when the inductive coupling system tends to be stable with its waveforms, this small-sized H-shape CPT system has been analytically considered and modelled in a finite-element method (FEM) environment, resulting in a maximum system efficiency of 59.5%, a coil transmitting efficiency of 83.8% and a maximum power output of 42.81 kW on the load end when the resonant coupling of CPT system tends to occur within a range of calculated resonant frequencies, with an air gap of 10 mm. Moreover, the system efficiency and coil transmitting efficiency can reach 47.75% and 77.22%, respectively, and the highest RMS real power to load can achieve 31.95 kW with an air gap of 20 mm. Besides, with an air gap of 30mm, this H-shape CPT system is measured to output 20.39-kW RMS power, along with the maximum system efficiency and coil efficiency of 41.78% and 63.23%, respectively. Furthermore, the improvements of flux linkage, magnetic flux density regarding the actual electromagnetic performance produced and the issues on the calculated natural resonant frequencies have been studied by result analysis and comparison of electromagnetic field parameters generated. In addition, the current limitations and further design considerations have been discussed in this paper.

Review on Stationary CPT Technologies and Coil Designs for EVs

“…In most small-scale low-power CPT systems for portable electronic devices like cell phones, wireless charging pads with coreless coils can acquire more popularity due to pursuits of relatively thin and lighter design from real-world customers, certainly under acceptable conditions such as charging power rating and basic efficiency to be at least satisfied by manufacturers' efforts on advanced electronic circuitry and control unit designs. However, high-power CPT applications are more supposed to need cores to assure the satisfactions of the overall system performance [38,39], for instance, the circular coil couplers with solid ferrite pads could form the flux distribution much better. A design of circular coil with ferrite pad is shown in Figures 3 &4 [10], in which the dimension is in mm.…”

“…A novel H-shaped coupler with ferromagnetic materials as cores was proposed in [39,49]. In order to enhance the magnetic field flux density and CPT coupling performance, different core materials were tested and analysed.…”