A Double Stator Through-hole Type Contactless Slipring for Rotary Wireless Power Transfer Applications

Contactless sliprings provide a safe and reliable power transfer solution with low maintenance for rotary applications. The magnetic design is a critical part of such a contactless slipring system (CSS). This paper presents a double stator design of a CSS for transferring power to rotatable loads and compares it against existing coaxial and face to face CSS systems. The magnetic coupling coefficient of the proposed system is improved greatly by having two stationary parts and a single rotatable coil sandwiched in between. An accurate 3-D-FEM modeling is developed to analyze the magnetic coupling characteristics of the system, and a practical prototype is constructed to evaluate its actual performance. A method of shielding the stray magnetic field using aluminium and ferrite materials has been presented. As a unique feature of the proposed structure, the magnetic coupling between the primary and secondary is constant for any angle of rotation. Moreover, the proposed system is robust and easy to assemble mechanically as the rotating part is just a single coil without any rotating ferrites. Simulation and practical results show that with the same core geometry and an extra coil, the new system is able to transfer about four times more power than a typical existing contactless slipring design.