Capacitive wireless power transfer systems: Applications, new coupler design and analysis of external factors

Capacitive power transfer (CPT) technology is becoming increasingly popular in wireless charging applications. This technology provides contactless power transfer from one point to another using an electric field between the metal plates. This thesis introduces CPT technology in terms of a wide range of perspectives such as basic principles, applications, a novel capacitive coupler design, and the effects of external factors on the behaviour of CPT system. The main purpose of the thesis is to study on capacitive coupler structures. For this reason, a new capacitive coupler design is proposed for CPT applications. A 110-W four-plate CPT system has been built to validate the proposed coupler structure. The obtained results show that the proposed capacitive coupler structure via its bent sections provides many advantages such as higher power level, lower required inductance, lower cost, and space-saving for CPT applications. Then, four-plate capacitive coupler structures are considered to evaluate the changes in coupling capacitances during temperature and humidity variations. The temperature level is set from 25 to 105 °C and adjusted with an increment of 10 °C thanks to the temperature controller. The humidity levels are evaluated within 43-80 % RH levels. According to the results, temperature rising is inversely proportional to the coupling capacitances for both coupler structures. On the other hand, the humidity variations are directly proportional to the coupling capacitances. To sum up, this thesis study has demonstrated that the capacitive coupler structure plays a critical role in the CPT system.