Efficiency study of coaxial contactless power transmission for electric railway

A novel contactless power supply system for electric trains is discussed based on structure of an air gapped coaxial transformer. Theoretical analysis, simulation results and verification experiments were conducted and the results are shown in this paper. The 94.0% efficiency was observed with air gap coaxial structure. Moreover, the power factor corrector (PFC) circuit are introduced to increase sending power. However, the efficiency drops to 86.8% for the internal resistance (ESR) of inserted parallel capacitor C_p. In order to reduce the effect of ESR, parallelization of C_p are introduced. This method achieves power transmission efficiency of 88.0%.