Contactless Energy Transfer Techniques for Industrial Applications. Power and Data Transfer to Moving Parts

Abstract

Contactless energy transfer (CET) systems are gaining increasing interest in the automatic machinery industries. For this reason, circuit equivalent networks of CET systems considered in the literature are introduced with emphasis on their industrial applicability. The main operating principles and the required compensating networks, along with different topologies of power supplies optimised for wireless powering, are discussed. The analysis of the wireless transfer, at the maximum efficiency, of high power levels shows that, in the kHz range, highly coupled inductive links are needed and soft-switching power sources required. The employment of CET units in controlled systems requires combining a link for data communication with the wireless power channel. At low frequencies, capacitive and inductive couplings are integrated in a unique platform to implement the wireless data and power links, respectively. Differently, at UHF, an increased data channel transfer efficiency is made possible by exploiting auto-resonant structures, such as split-ring resonators instead of capacitances, one at each far-end side of the link. The design procedure of a power CET system, including the dc/ac converter, a rotary transformer and its windings, is discussed and the results presented. A different version of a WPT system, which involves multiple transmitting coils and a sliding receiver, is also presented. A low frequency RFID capacitive data link is then combined with the rotary CET unit to provide the temperature feedback of a controlled system, wherein the rectifying part of a passive tag is exploited to simultaneously power and read a temperature probe. Subsequently, a split-ring based near-field UHF data link is designed to ensure an improved temperature detection in terms of accuracy and resolution. The sensor readout is performed at the transmitter side by measuring the reflected power by the load rectifier.