Review of Segmented Stator and Rotor Designs for AC Electric Machines

Using segmented-cores for the production of electric machines provides several advantages like simplified winding process, ease of transportation, assembling the machine, ability to use different materials for stator and rotor, including oriented steel, while reducing the scrap or increase in reluctance torque. In literature different types of segmented stator designs were used for different operations, for example some operations may require better cooling of the machine, some require lighter weight machine and in some cases higher slot fill factors are desired. There are also some possible disadvantages of using segmented stators, like increase in cogging torque, increase in acoustic noise, decrease of average torque, higher saturation in the machine or increase in cut edges as compared to conventional whole stator. Punching leads to changes in the magnetic and loss characteristics of the region close to the cut edge of the steel. Accurate modelling of segmented stators, using FEA is challenging as segmentation leads to more cut edges as compared to whole motor. This paper reviews the information presented in literature for different types of segmentation in the permanent magnet synchronous machine (PMSM) or switched reluctance machine (SRM), effects of segmentation on the torque ripple and core losses, design modifications in segmented machines for improving the performance of the machine and modeling of segmented machine using FEA. This provides a stepping stone information to the machine designer for the design of segmented stators.