Enhanced Ventilation and Thermal Performance by Inclined Through Holes on Rotor Yoke in Permanent Magnet Synchronous Wind Generators

The cooling performance of medium-speed permanent magnet synchronous wind generators (MS-PMSWGs) is critically important, as it determines the sustained output power and reliability. This paper proposes a novel rotor structure featuring inclined through holes, which based on forced air-cooling method. On the one hand, the through holes provide additional flow paths for cooling air, effectively reducing flow resistance. On the other hand, as the rotor rotates, a pressure difference is created between the two ends of the holes, which generates the airflow independently. To accurately calculate the flow and thermal fields, three-dimensional (3-D) computational fluid dynamics (CFD) models have been established. Using the basic design of a 1.5 MW MS-PMSWG, a comparative analysis is conducted between the conventional structure and the proposed design. Under rated operational condition, the pressure required for the cooling fan to generate the same flow rate is significantly reduced by the adoption of the proposed holes, as well as the temperature rises of the windings and permanent magnets are reduced. Moreover, under the fault condition with the fan shutdown, the operational capability is greatly enhanced, attributing to the airflow generated by the rotating holes. Furthermore, reduced scale prototypes are built adhering to the principles of Reynolds similarity, and the effectiveness of the proposed structure is experimentally validated.