This paper presents a robust optimal design method using a hybrid response surface method (H-RSM) which directly finds an optimal point satisfying a target Z-value or a probability of failure. Through three steps, this paper achieves the goal that is to increase the open-circuit airgap flux (OCAF) in a surface-mounted permanent magnet motor and decrease its variation caused by variations of the airgap lengths including an additional one between permanent magnets and rotor back yoke. First, the OCAF equation is derived from the magnetic equivalent circuit (MEC) considering the additional airgap. Then, the equation is validated by comparing its results with those of the finite element method (FEM) modeled by the slotless stator. Next, the tolerance sensitivity analysis, using the partial derivative of the OCAF equation with respect to the airgap length, is performed to investigate the effects of design variables on the OCAF. It is shown that increasing the magnet thickness is effective for both increasing mean of the OCAF and reducing its variation. Finally, robust optimal design is performed using the H-RSM, in which all data are obtained from the FEM modeled by the slotted stator. The results of the robust optimal design are verified using the FEM.
The study compares the sensitivities of open-circuit airgap flux (OCAF) between a surfacemounted permanent magnet (SPM) machine and a spoke-type PM machine based on variations in airgap length including additional airgaps between permanent magnets and rotor core and between segmented stator cores to achieve high quality electric machines. Analytical equations deduced from magnetic equivalent circuits (MECs) are used to directly compare natural-born characteristics of the OCAF of the two machines. First, the MEC of each machine is modeled by considering two additional airgaps between the PMs and rotor core and between the segmented stator cores. Second, the OCAF equation of each machine is derived from the MEC to analyze the effects of the design variables on the OCAF. Subsequently, the partial derivative equation of the OCAF equation with respect to the airgap length is obtained for sensitivity analysis. A comparison of the equations of the two machines indicates that the spoke-type PM machine exhibits inherently higher sensitivity and average value of the OCAF when compared to that of the SPM machine. Finally, the results are validated via a two-dimensional finite element method (FEM) by considering the variations in airgap lengths.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.