Multi-objective optimization of stator direct cooling for direct-drive permanent-magnet wind generators

In order to make full use of the heat dissipation advantage of the evaporative cooling technology under the high heating load for electrical machines, the analysis and multi-physics coupling optimization for a 10MW direct-drive surface-mounted permanent-magnet (PM) wind generator with stator direct cooling method are proposed in this paper. First of all, the interrelation between multi-physics fields in evaporative cooling wind generators (ECWGs) is studied. Then the heat convection performance of hollow conductors under the influence of fluid-thermal coupling is studied based on the small inclination angle self-circulation cooling experiment. Next, the multi-objective optimization model with two different stator inner direct cooling modes is proposed to achieve the lightweight and cost reduction design of ECWGs. The optimization of a 10 MW direct-drive PM wind generator is carried out and the electromagnetic and cooling performance are investigated by the FEA module to verify the correctness of the results in this paper. Finally, the optimization results with single in-winding cooling and hybrid in-iron and in-winding cooling are compared and analyzed based on the weight, price, cooling, and electromagnetic performance to demonstrate the advantages of the hybrid cooling method in lightweight design optimization of ECWGs.