Electromagnetic Analysis and Experimental Testing of a Flux Focusing Wind Turbine Magnetic Gearbox

The electromagnetic design of the second stage of a 59:1 multistage magnetic gearbox for a wind turbine demonstrator is presented. The multistage series connected magnetic gearbox is composed of a 6.45:1 first stage and 9.14:1 second stage magnetic gear. The magnetic gears utilize a flux focusing spoke type rotor typology with a unique segmented fully laminated design. The electromagnetic impact of structural design changes on the second stage gearbox is considered with respect to torque density. Severe three-dimensional edge effects were encountered that greatly reduced the expect torque density of the second stage magnetic gear. Experimental testing of the multistage magnetic gear highlights unexpected problems associated with eddy current loss and torque ripple.