Analysis of Contact-Less Power Transfer Characteristics in a Periodically Connected Drill Pipes Based on Measurement of Coupling Unit

In order to search the under-ocean floor, an ultra-long drill pipe is used to dig a deep hole. It is made of short (e.g. 10m long) pipe, screwed in one by one to make a long one. The necessary electric power for driving sensors or the communication system around the drill tip may be transferred contactless through drill pipe junctions. As one of the simplest and efficient means of contactless power transfer, a pair of coupled coils is employed at each junction. In order to analyze power transfer in the long pipe, the periodic circuit theory is useful, and a generalized theory is proposed to analyze any complicated coupling, such as parasitic resonance circuit.