Maximum Power Transfer versus Efficiency in Mid-Range Wireless Power Transfer Systems

• Published in: Journal of Microwaves, Optoelectronics and Electromagnetic Applications Optoelectronics and Electromagnetic Applications, 2015-06, Vol.14 (1), p.97-109
• Main Authors: Abatti, Paulo J., Pichorim, Sérgio F., de Miranda, Caio M.
• Format: Article
• Language: English
• Subjects: ENGINEERING, ELECTRICAL & ELECTRONIC; Maximum power transfer; OPTICS; power transfer efficiency; relative power transfer; wireless power transfer
• ISSN: 2179-1074; 2179-1074
• DOI: 10.1590/2179-10742015v14i1433

AbstractThe condition for maximum power transfer of 2-coils wireless power transfer (WPT) system is derived from circuit analysis and discussed together with the respective WPT system efficiency (η). In the sequence, it is shown that a 4-coils WPT system (which can be divided in source, two communication and load circuits) without power losses at the two communication circuits (ideal 4-coils WPT system) presents, from maximum power transfer and efficiency point of view, a performance similar to those of a 2-coils WPT system. The exception is the influence of coupling coefficient (k): in 2-coils system η increases as k approaches one, while in ideal 4-coils WPT system η increases as k between the two communication coils approaches zero. In addition, realistic 4-coils WPT systems (with power losses at the two communication circuits) are also analyzed showing, for instance, that η presents a maximum as a function of k of the communication coils. In order to validate the presented theory, 4 coils were built, and a setup to perform 2-coils and 4-coils WPT systems has been carried out. Practical results show good agreement with the developed theory.