Design and Experimental Investigation of an Additively Manufactured PMSM Rotor

This paper describes the design, construction and manufacturing process of an additively manufactured (AM) permanent magnet synchronous rotor with interior magnets. After this, the AM rotor is mounted into a conventional stator and tested under load and no-load. The rotor active part is manufactured from soft-magnetic ferro-silicon alloy using the powder bed-based AM technology of laser beam melting (LBM). The so-called AM functional rotor model is both designed with extended functionality and with an increased lightweight level. Therefore, the functional model is continuously skewed and its performance is compared to a non-skewed and a step-skewed rotor. In order to reduce eddy current losses, the surface of the functional model was grooved. Furthermore, a new design of the rotor end section is presented. The weight and the inertia of the rotor are reduced by implementing lightweight AM structures, a hollow shaft and a new conical transition region between the active part and the bearings. The building process and design adjustments in order to ensure a robust additive manufacturing process are presented, too. Finally, measurements show that this new design significantly reduces the amplitude of the torque ripple. In summary, the torque of the motor is increased and the mechanical time constant is decreased by inertia reduction.