Mechanical design considerations of a double stage axial-flux PM machine

This paper evaluates the mechanical design and construction of a 300 kW, double-stage, axial-flux permanent magnet (AFPM) machine. Finite element simulations were used to determine the severity of the attraction force between the rotor discs. The huge attraction force also caused problems during machine assembly, because the closer the discs are brought in, the larger the force. The results obtained from the simulations suggested an increase in yoke thickness in order to withstand the attraction force on it. The simple lumped parameter thermal model was established to evaluate the effectiveness of the air-cooling, which is compared with measurements taken on a prototype AFPM machine