Investigation of a Low-Speed High-Torque-Density Direct-Drive External-Rotor PMSM for Belt Conveyor Application

Aiming at the shortcomings of complex mechanical transmission structure and low efficiency of the existing belt conveyor driven by asynchronous motor, this paper focuses on the investigation of a new type of low-speed high-torque-density direct-drive permanent magnet synchronous motor (LHDPMSM) for driving the belt conveyor. The proposed LHDPMSM utilizes external rotor structure to achieve the goal of fully direct drive of the belt conveyor. First, the topology and advantages of the straight-shape external-rotor LHDPMSM is introduced. Then the selection rules of the pole-slot combination are studied. Furthermore, an improved subdomain model is established based on the idea of segmentation for fast calculation of the no-load magnetic field of the proposed straight-shape external-rotor LHDPMSM. Moreover, the operating performance of the proposed LHDPMSM with load fluctuations was verified by FEA. In addition, an efficient cooling system based on $Z$ -shape water channels and hollow shaft was designed, and a LPTN model was established for temperature fast calculation. Since the cooling system has a negative impact on the shaft mechanical strength, the mechanical strength of the shaft and other fragile components of the LHDPMSM was analyzed to ensure the safe operation of the motor. Finally, a prototype is manufactured and tested to validate the design concept introduced in this paper.