An automated design procedure for the power density optimization of IPM machines

This paper presents a multi-physics design procedure for the power density maximization for Interior Permanent Magnet (IPM) machines. This goal is pursued by increasing the mechanical speed as well as the electromagnetic torque capability. At this purpose an automated design procedure aided by an optimization algorithm is developed: both electromagnetic and structural problems are taken into account by means of fast Finite Element (FE) magneto-static simulations together with a simplified analytical model for the mechanical sizing. Since the magnets are placed within the rotor iron, retaining sleeves are avoided and the motor integrity against centrifugal forces is guaranteed by the proper sizing of the rotor structure. The procedure allows to automatically find the maximum output power obtainable for a given machine volume; moreover it outputs the maximum value of rotational speed above which no further improvements on output power can be achieved.