Development of a high performance magnetic gear

This paper presents calculation and measurement results of a high performance permanent magnetic gear. The analysed permanent magnetic gear has a gear ratio of 5.5 and is able to deliver 27 Nm. The analysis has shown that special attention needs to be paid to the system where the gear is to be installed because of a low natural torsion spring constant. The analysed gear was also constructed in practice in order to validate the analysis and predict the efficiency. The measured torque from the magnetic gear was only 16 Nm reduced by the large end-effects. A systematic analysis of the loss components in the magnetic gear is also performed in order to figure out why the efficiency for the actual construction was only 81%. A large magnetic loss component originated in the bearings, where an unplanned extra bearing was necessary due to mechanical problems. Without the losses of magnetic origin in the bearings and less end-effects caused by relatively short stack, an impressive efficiency estimated at 96% can be obtained. Comparison with classical mechanical gears have shown that the magnetic gear has a better efficiency and a comparable torque per volume density. Finally it is concluded that the result in this paper may help to initiate a shift from mechanical gears to magnetic gears.