Three-Phase Air-Core Rotary Transformer with Halbach AC Windings for Wound-Field Motors

This paper proposes a three-phase air-core rotary transformer that applies Halbach AC winding technique. The air-core structure increases the leakage flux and reduces the magnetic coupling between power transfer coil and receive coil. To solve this problem, an asymmetric magnetic field distribution in which flux is concentrated only on the surface where these two coils face each other is realized in the Halbach AC windings. This paper first explains the technique of how to construct an asymmetric magnetic field distribution only with coils. Then, the verification test using the prototype will be conducted. The current waveforms when the receive side is rotating through the slip-ring are also evaluated and their results are reported.