R&D of Non-Contact Rapid Charging Inductive Power Supply System for Electric Vehicles
In recent years, there have been increasing demands on automobile manufacturers to develop vehicles incorporating a clean power source to replace the conventional internal combustion engine. Among the several alternatives to the internal combustion engine that have been studied, the research and development of electric vehicles has continued for decades as a candidate system. Due to limited battery capacity and charge performance, however, electric vehicles have not really taken off. Given this background, our research group has developed a non-contact rapid charging inductive power supply (IPS) system with safe, simple, and rapid recharging characteristics for electrically driven vehicles (principally for electric vehicles and plug-in hybrids). Outstanding features of the system include high efficiency, significant weight reduction, and a long air gap, and have been implemented through the optimization of the shape of the track and pickup part. This paper mainly focuses on the results of performance evaluation tests of the developed system. The results obtained are listed below. a) The design optimization of the track/pickup part for an IPS having a plane core and round shape was conducted by means of finite-element electromagnetic field analyses in consideration of externally driven circuit. Based on this study, we arrived at parameters such as drive frequency (22 kHz), inner core diameter (90-mm radius), and core thickness values (4.0 mm for the track side, 2.0 mm for the pickup side). b) Based on the results of electromagnetic field analyses, an actual IPS was fabricated. Through non-contact power transmission experiments, the attainment of a 92% total efficiency was confirmed during 30 kW power transmissions. Also, slimming (33 mm), weight reduction (35 kg), and a long air gap (100 mm) were successfully accomplished. c) The developed IPS was installed on an electric micro-bus. Non-contact power transmission was conducted, and the successful recharging of the on-board battery was confirmed. d) With regard to the benefits of implementing the IPS in an electric car, calculations were conducted using regional urban runs as a model. Under the operating conditions studied in this project, it was concluded that an approximately 9% reduction in electric power consumption can be achieved through a 474-kg reduction in vehicle weight. e) Taking advantage of the increased flexibility in weight resulting from implementation of the IPS, it was determined that a narrower SOC operating range can easily be achieved for the purpose of prolonging battery life.
Poster presentation: Electronics