Thermal and mechanical design considerations for a switched reluctance motor

This paper describes mechanical and thermal design aspects of a 5 kW Switched Reluctance Motor. In Switched Reluctance Motor (SRM), the rotor neither has winding nor any permanent magnet in contrast to conventional Induction or permanent magnet machines. Although, this considerably simplifies the mechanical design, high current densities in the stator generate a substantial amount of heat. It is, therefore, imperative to drive this heat out of the motor for continuous and safe operation. Air cooling for the stator is preferred due to simplicity and cost considerations. The paper is divided into two parts; the first section describes the fin selection criteria for the stator housing. Here, three fin geometries are analyzed; plate, slotted and pin fins. For each geometry, a parametric study of temperature distribution inside the SRM with respect to fin dimension has been done numerically and presented so as to arrive at the optimum fin height. It is found that slotted fins offer the highest heat dissipation rate compared to pin and plate fins due to increased exposed surface area. The second section focuses on the mechanical design aspects of SRM with emphasis on design for manufacturability and component assembly. Aluminum fin arrays are proposed to be installed on the stator to facilitate heat transfer to the ambient air.