A contactless slipring system by means of axially travelling magnetic field

This paper presents a three-phase contactless sliprings system based on axially moving magnetic field. The contactless slipring is a new alternative to conventional slipring systems for transferring power to and from a rotating shaft. To increase the power transfer capability of single phase pulsating field-based contactless slipring systems, this three-phase travelling field-based system is proposed for rotating applications such as wind turbine pitch control systems.Complete analytical expressions are derived for system performance analysis. A 3-D FEM (Finite Element Model) is developed, and simulation study conducted for system assessment and verification. A method of canceling the mutual inductance between the primary phases is proposed and practically verified by testing a prototype model. It has been shown that the proposed system can transfer up to 2096 Watts of power to a load at the secondary circuit with a quality factor QS of 9.8. The maximum power efficiency of the system is about 95.8% over a large air gap of 22.5 mm. A 3-D FEM thermal model is developed and simulated as a coupled analysis with the magnetic model, and it has been found that the temperature rise is only 4.5°C in an hour under maximum power transfer conditions. The FEM simulation results show that the travelling field-based system can transfer about 15.64 times more power than the counterpart pulsating field-based system at a much higher efficiency.