A novel detached magnetic coupling structure for contactless power transfer

A contactless slipring offers an alternative solution to a mechanical slipring for power transfer, and magnetic coupling is the key part of the system. This paper proposes a novel detached magnetic coupling structure used for contactless sliprings systems. To minimize the losses and increase the power transfer capability, a magnetic coupling structure with unique core geometry is proposed for a rotating transformer to transfer electrical power between the two parts. A Finite-Element-Boundary-Element (FEM-BEM) model is developed and FEM analysis conducted. The proposed contactless slipring system has been verified by simulation. The output power, efficiency, voltage gain and current gain are presented to assess the performance of the system. It has been found that the fringing flux on the windings affects the conduction losses and the EMI greatly, and it can be reduced by placing the winding away from the air-gap of the core. Practical design considerations as well as the advantages of the proposed structure as compared to a typical coaxial design of rotating transformer have been discussed. It has been shown that the proposed coupling structure can deliver up to 4.35 KW of power at a 25 Ω resistive load. An excellent magnetic coupling coefficient of 0.92 is achieved as a result of the specific core geometry with a single air gap. The voltage gain for this system is 0.83, which indicates a low internal voltage drop on the coupled coils.