Impact of a Bonded-Magnet Adoption on a Specific Fractional Motor Power and Efficiency

The problem of evaluating the impact on the efficiency consequent to the adoption of bonded magnets in substitution of ferrites in small permanent-magnet machines is faced. That is necessary for the development of the main object of this paper: The evaluation of the obtainable performances of a specific brushless dc motor fractional motor through simple substitution of bonded magnets proposed by the authors to the ferrite magnets used up to now. The final aim is to make clear the practical adoptability of the proposal. Several prototypes produced in the authors' laboratories have been tested, and a long experimental activity has been carried on. In particular, the focus of the work has been the identification and separation of the iron losses, both hysteresis and eddy currents, from the contribution of the bearings. The corresponding torques have been calculated, and the energetic behaviors of the original machine with ferrites and the prototypes with phenolic bonded magnets have been analyzed. The satisfactory impact on the efficiency and the improvement of the output power of the motor with bonded magnets let possible to consider the analyzed solution as realistically adoptable.