Magnetic and Thermal analysis of loaded pickups for Inductive Power Transfer systems

Abstract

Inductive power transfer (IPT) technology is a wireless power delivery method where power is effectively transferred to any moving or isolated system. The lack of physical connections between the power delivering and receiving systems makes IPT an attractive solution for powering systems in harsh environments such as underwater and mining applications. Contactless battery charging of electric vehicles and monorail systems for material handling are some current commercial IPT applications. Note that several of these applications were developed primarily from research conducted at The University of Auckland. This thesis presents the magnetic and thermal analysis of loaded pickups for IPT systems using JMAG Studio 10.0TM, a three dimensional finite element method software package. Research conducted by the Power Electronics Group at The University of Auckland confirms the accuracy and reliability of JMAG Studio software package in modeling IPT systems. E and Flat-E pickups used for various industrial applications are compensated using series, parallel, LCL and LCLC tuning topologies. For both the pickups, it has been observed that there is little difference in the losses in the pickup shape for the four tuning topologies. Thus, for the analysis of the remaining five monorail pickup shapes, the preferred and traditional parallel tuning topology is used. The power performance for the six different monorail pickup shapes can be enhanced by modifying the ferrite shape. In this thesis, this is achieved through scripting, using commands from JMAG Studio. Through scripting, the dimensions of the pickup model can be easily varied and the physical re-construction of the model is not required. The losses within the ferrite structure and coil of the pickup are compared for the seven pickup shapes. The temperature distribution of the pickup surfaces is obtained for different quality factors, resonant tank current and delivered output power conditions. The highlight of this research is that a script file has been developed to model the temperature of pickup surfaces for different load and compensation conditions. It is hoped that this will play an important role in addressing commercial interest in the heating of IPT pickups when they deliver power.