Study of the Effect of a Shielding Cylinder on the Torque in a Permanent-Magnet Synchronous Machine Considering Two Torque-Producing Mechanisms

Despite an ever-growing interest, a lot of questions related to the design and operation of high-speed permanent-magnet synchronous machines remain unanswered. One aspect of such high-speed machines that requires special attention is the effect of the shielding cylinder (SC), a conductive sleeve that is wrapped around the magnets and which' goal is to reduce the rotor losses and/or retain the magnets. Therefore, this paper aims at theoretically studying the effect of the SC on the torque production. The study is performed using a 2-D analytical subdomain model that accounts for slotting and the eddy-current reaction field. The torque is divided in two components, the classical torque due to interaction between the magnets and the stator currents and the torque due to interaction with the eddy currents in the SC. This approach is unique and results in a better insight in the machine's physics.