Thermal analysis of direct-drive offshore permanent magnet synchronous generator with peak–valley heat sinks

Aiming at the heat generating problems of high-scale offshore wind generator with diagonal-axial ventilation structure (DA-VS), an offshore inner rotor permanent magnet wind generator (OIR-PMWG) with a 5MW rated power is taken as the research object. Firstly, based on the basic theories of fluid dynamics and heat transfer, a three-dimensional physical and mathematical model of fluid–heat-coupled for offshore inner rotor permanent magnet wind generator (OIR-PMWG) with diagonal-axial ventilating structure is established which is solved by the finite volume method. In this paper, in order to improve the thermal performance of offshore wind generator, two alternating peak–valley heat sink structures, PartB and PartC, are proposed. The effects of the alternating peak–valley heat sink schemes on the velocity distribution of the fluid between the fins and the temperature rise of the important generator’s parts are investigated. Among them, the PartC scheme is able to increase the fluid velocity between the fins by 11.5% and reduce the winding temperature by 9.6 °C. The alternating peak–valley heat sink schemes proposed in this paper can redistribute the flow rate and air velocity between the heat sink, improve the efficiency of the ventilation system, and provide a reference for the design of ventilation and cooling structures for offshore wind generator.