Comparison of Outer- and Inner-Rotor Switched Reluctance Machines

In applications with high torque requirements an outer-rotor design has several advantages compared to an inner- rotor one. A feasibility study of both designs for an in-wheel direct drive application is presented. The torque density depending on slot area, fill factor and air gap radius is analyzed. The influence of cooling on the torque capability of the inner- and outer-rotor machine is shown. A comparison of the thermal behavior will show if the cooling of the outer-rotor machine is adequate for high torque applications. Finite element simulations, linked with analytical software are used to calculate and compare the torque of the machines.