Internal Ventilation and Thermal Characteristics of a New Ventilation System for a Large Offshore Permanent Magnet Wind Turbine Generator

The large offshore direct-driven permanent magnet wind turbine generator operates in complex and changeable operating environment. Once the overheating problem occurs, the generator will lose its magnetic field and burn down seriously. Therefore, it is very important to study the ventilation and thermal characteristics of the large generator. In this paper, an omnidirectional ventilation and cooling system with bevel arrangement of inlet and outlet is proposed by taking the 5MW direct-driven permanent magnet wind generator as an example. According to the structure and parameters of the prototype, a calculation method of coupling the generator global ventilation network model and 1/16 local fluid-heat transfer numerical model is proposed. Firstly, the global area ventilation network model of the rotating generator is established, and the operating point of the unit ventilation system is calculated. Secondly, a 3-D fluid and heat transfer coupling model of the generator in the full axial direction and 1/16 of the circumference is established. Based on the calculation results of the ventilation network, the temperature field of the 3-D local model is solved, and the accuracy of the calculation method is verified by tests. Finally, the temperature variations of the key components of the stator and rotor of the generator under different operating points of the internal ventilation system such as air volume and inlet air temperature are studied, which provides a theoretical basis for further improving the ventilation design of large offshore wind turbine generators.