Optimization of rotary transformer for RUM with secondary self-compensation

In rotary ultrasonic machining (RUM), the rotary transformer can replace the well-established slip ring technology to supply contactless power for the revolving transducer. Such contactless energy transfer (CET) is safe and high rotation speed of the spindle is permissible. However, the transfer efficiency and output power are usually a pair of contradictions. In this paper, the self-compensation method is adopted on secondary side in order to improve the dynamic balance of the revolving part. Considering the distinct capacitive behavior of the transducer, two primary compensation topologies are given. The mathematical models are presented to identify the power transfer efficiency, transfer capability and load impedance of rotary transformer used in RUM. The effects of coil turns on transfer efficiency and load resistance are researched. An optimization method of rotary transformer used in RUM is put forward. A contactless power supply RUM system that can produce high speed, high efficiency and high output power is therefore possible. (C) 2017 Published by Elsevier GmbH.