Ventilation and heat transfer in Axial Flux Permanent Magnet Generators

Axial flux permanent magnet generators are used in various applications due to their compactness and high torque/weight ratio. The possibility of accommodating a large number of poles makes them the ideal option for low speed applications. Due to the relatively recent interest in this kind of machines, efforts have been concentrated in the electromagnetic design, whereas the thermal aspect has not been completely investigated yet. Cooling of an AFPM generator is generally provided by forced convection: fresh air enters the generator axially and leaves it radially through the cavities between the magnets and the stator windings. Heat generated in the stator windings is therefore dissipated by the air flowing through the machine. 2. Why? Thermal analysis of the AFPM machine is important not only to foresee the operating temperature of critical components such as insulating materials, lubricants and permanent magnets to guarantee their correct operation, but also because the generators efficiency depends on these temperatures. Cummings Generators Technologies (CGT) are currently manufacturing various types of AFPM generators and they are interested in a fast and reliable method to predict the heat transfer inside their machines. For this purpose a Lumped Parameter model will be built to calculate heat transfe