This paper presents an optimization design and experiment of a high speed motor (HSM) for underwater thrusting systems by using magnetic flux density distribution (MFDD) of the stator, based on finite element
analysis (FEA). The MFDD in the HSM is closely related to the electro-magnetic loss. This is an important factor when considering increasing efficiency, miniaturization, and reducing overall weight. To this end, a volumetric design of the rotor, which directly affects the magnetic flux density (MFD), was carried out using torque per rotor volume and a design line of electro-motive force. Calculation of the MFDD of the stator was derived from the area of the triangular element by the 2-D finite element method using the element node and the center of gravity. The flux density inside the element was derived by FEA. The maximum density distribution (MDD) and average density distribution (ADD) of the MFDD for the variable area (yoke, tooth, and shoe) of the stator core are presented. Efficiency optimization was performed by calculating the iron loss and efficiency reduction ratio using the ADD. On the basis of the manufactured 2.5 [kW] HSM, the optimal design of the MFDD was verified by comparing the FEA results with the experimental results at the rated operating point.