This chapter focuses on mid-range wireless power transfer (WPT) systems applied to electric vehicle (EV) battery chargers. The WPT is recently considered as an efficient electric energy transfer process between two or more points in space, without wiring. The technology associated with each specific process of WPT differs from case to case depending on the distance between those points and the power to be transferred between them. The widely adopted distance categories are named short-range, mid-range, and long-range. The short-range is normally defined as up to a few millimeters range. The mid-range is between a few millimeters and a few meters. The long-range distance is defined as a longer than that of the previous category, stretching up to a few kilometers.
Top1. Introduction
To summarize the state-of-the-art of the Wireless Power Transfer (WPT), it must be said that one important aim of the WPT is the mobility, i.e. the transport. The evolution of the modern transport sector is determined by two paradigms: the climatic changes driven by pollution and the geopolitical instability in the main geographic areas, where crude oil is currently produced (Turton & Moura, 2008) The oil is still the most important means for the transport propulsion, but now the “green car” is being introduced, driven by the so called “green”, non-polluting energy. The name “green cars” is not only tagging the passenger cars, but is also used for other vehicles, like long distance trucks, for example. The meaning of “green” expresses mainly the electrification of any mobility, and the road transport, in particular
(Perlo & Meyer, 2012; Eckman, 2011). The final goal of the electrification is the integration of the vehicles into intelligent electrical systems that include the transmission and storage of energy for sustainable applications (Perlo & Meyer, 2012).
This chapter focuses on mid-range WPT systems and especially on their efficiency improvement. The technology, associated with the WPT process varies, depending on the distance and the power to be transferred (Romba et al., 2017). The distance defines three main categories, named: short-range, mid-range and long-range. The short-range is normally defined as up to a few millimetres range. The mid-range is between a few millimetres and a few meters. The long-range distance is defined as a longer than that of the previous category, stretching up to a few kilometres or even more. The technology solutions, used for short-range distances are the inductive power transfer (IPT) and capacitive power transfer. The main part of the solutions for WPT aimed at the mid-range distance is based on magnetic resonance coupling and high switching frequency of the power electronic converter (Romba et al., 2017; Huang et al., 2012; Baikova et al., 2016). The long-range distance WPT requires more narrow concentration of the electromagnetic energy, to avoid the unselective dispersion of the electromagnetic energy in all directions. That beamed power transfer is known since the 1960s, but still it is not enough mature technically for a practical implementation (Glaser, 1968). This technology is also a basis for the idea presented by some researchers and enterprises, known as the solar power satellite system. This concept, introduced by Peter Glaser in 1968, is based on geosynchronous orbit satellites, as transmitters of microwave electromagnetic energy (Glaser, 1968). The energy is obtained from extremely large, kilometric size solar panels, mounted in the space, while the receivers are mounted on the Earth surface. The microwaves beam or the laser beam will be sent to the receivers, supposed to be made as a rectenna system that combines antennas with rectifiers (Glaser, 1968; Bareiss et al., 2013). The different constructions of WPTs depend on the applications, the distances and the power that different classes of vehicles require. The chapter concerns the Wireless Power Transfer Systems efficiency improvement, using the matching of impedances made by a different device, named Magnetic Core Reactor. In addition, a comparative study of the magnetic field behaviour of two type of coils, spiral coil and helicoidal coil, is presented.