Lumped-parameter-based thermal analysis of a doubly radial forced-air-cooled direct-driven permanent magnet wind generator

A lumped-parameter-based thermal analysis of a direct-driven permanent magnet wind generator with double radial forced-air cooling is presented. In the proposed thermal model, the thermal conduction and convection as well as the heating of the cooling fluid are modeled in terms of thermal resistances. The electromagnetic losses of the generator are calculated by a two-dimensional, non-linear, time-stepping finite element method. The developed thermal calculation model can be applied both to static and transient problems. The performance of the proposed thermal model is compared with the results calculated by using computational fluid dynamics. The presented modeling strategy is implemented into an analytical calculation tool, which is used in the design process of a 3.35 MW high-torque low-speed direct-driven permanent magnet synchronous generator. Experimental results for a 3.35 MW permanent magnet generator are presented.