Design optimization for the adoption of bonded magnets in PM BLDC motors

The increment of the manageable power in machines where the normally adopted ferrites are replaced with bonded magnets can vary and can introduce saturation problems depending on the variations in the magnetic circuit design. The saturation of the magnetic circuit distorts the phase voltages, introducing undesired harmonics in the connection to the mains. Combined modifications of both stator poles and rotor ring of a Brushless DC motor are proposed to evaluate their impact on the increment of the manageable power and on the harmonic content. Several magnetic circuit modifications have been considered and the paper presents the results of the most reasonable solutions, obtaining significant increments of the power. The activity is still carrying on and will take into account also the magnetization directions.