Influence of electrical steel grade on the temperature distribution in direct-drive PM synchronous generators for 5 MW wind turbines

The effect of the magnetic and thermal properties of 4 electrical steel grades were compared for a Permanent Magnet Synchronous Generator (PMSG). The low loss grades are expected to have less iron loss in the stator lamination, but their thermal conductivity may be lower. Therefore, the evacuation of the heat may be less effective. This has an influence on the temperature distribution, which is crucial in case of PMSG. The investigated generator is a 5 MW, radial flux machine designed for direct drive wind turbines. A thermal Finite Element Model was used to simulate the temperature distribution in the generator. The influence of the steel grade on the thermal distribution was compared for three geometries of PMSG with air gap diameter equal to 4, 6 and 8 meters respectively. In conclusion, for all three geometries, the thermal distribution is not dependent on the electrical properties, but mainly on the thermal conductivity of the steel.