Design, construction and measurements of a permanent magnet axial flux machine

The results of the design, the construction and first measurements of an axial flux permanent magnet (AFPM) machine are summarized. The goal of this project was to build an axial flux machine with surface mounted magnets in the simplest possible way to use the machine as a demonstrator for small wheel hub drives with a reduced torque demand. Therefore the machine was designed as double-sided motor with internal stator and tooth-coil winding to enable a modular structure and two rotor discs. For the ease of a simple integration of the machine, the outer diameter was limited to a certain value. Therefore the design yield to a machine with 12 poles and 18 stator teeth (number of slots per pole and phase q = ½). 3D-electromagnetic and 3D-thermal studies with the finite-element-method (FEM) software JMAG were carried out. After the design of the active elements, the construction of the prototype was done. The machine was build up on a test bench and coupled with a load machine to compare the simulation results with the measurements. The measurements show that the electromagnetic properties (torque, efficiency) fit with the simulation results, but due to the open ventilation motor design the thermal behavior of the machine is better than assumed for the simulations. With the results it is possible to estimate also the behavior of bigger wheel hub drives.