Analysis of Bridge Placement and Ferromagnetic Piece Curvature on Performance of Coaxial and Flux Angle Mapping Magnetic Gears

The main drawbacks of mechanical gears stem from the physical contact between teeth. Magnetic gears (MGs) achieve the same function as mechanical gears but use magnetic fields to transfer power between shafts. This paper examines how the thickness, position of a bridge, and curvature of ferromagnetic pieces (FPs) impact the electromagnetic performance of flux angle mapping (FAM) magnetic gears (MGs) compared to conventional coaxial magnetic gears (CMGs). The results show that, while a bridge on the inner radius of the FPs in a CMG has a minimal impact, even a thin bridge significantly degrades FAM MG performance. Curving the FPs has less effect on FAM MGs performance than even the thinnest of bridges and may facilitate their retention. Although all bridge positions affect the torque ripple, FAM MGs are especially sensitive to any bridge. A preliminary structural analysis was performed. With the exception of the alternating bridge (a bridge that moves from the inner edge to the outer edge after each FP), adding a bridge significanlty increases the stiffness of the FP rotor and reduces the deflection experienced by the FPs. Even without a bridge, FAM MGs experience significantly lower FP rotor deflection than CMGs due to forces on nearby FPs acting in opposite directions.