Performances of a Contactless Energy Transfer System for Rotary Ultrasonic Machining Applications

In rotary ultrasonic machining (RUM), the contactless energy transfer (CET) system based on the rotary transformer can replace the well-established slip ring technology to supply power for the revolving ultrasonic vibrator. However, the transfer efficiency and power output capability of the CET system is usually a pair of contradictions. The high voltage of the compensation element is prone to occur, especially in high power applications, which is dangerous. In this paper, for four basic compensation topologies, the mathematical models of the transfer efficiency, the load impedance and the compensation elements' voltages are presented. The compensation elements are optimized for improving the transfer efficiency. The effects of coil turns on the transfer efficiency, the load impedance and the compensation elements' voltages are researched. The coil turns are optimized to control the load impedance of the power supply and the voltages of the compensation elements. The experimental results basically agree with the theoretical results. The optimized CET system not only has high transfer efficiency, but also has high power output capability. At the same time, the high voltages of compensation elements are avoided effectively and the safety of the system is guaranteed.