Design for Manufacturability of a High-performance Induction Motor Rotor

A study is conducted on the state-of-the-art manufacturing practices of conventional industrial and research-and-development (R&D) firms manufacturing electric induction motors. It is found that current industrial processes cannot produce high-performance motors, and that current R&D processes are too costly. A new manufacturing process for fabricating the rotors of squirrel cage induction motors is developed. The new process addresses the issues raised by the study by delivering high performance at a reduced cost. The induction rotor manufacturing process presented involves using net shape processes to manufacture the parts which are manually assembled and subsequently joined. A squirrel cage of extruded chromium copper bars and end rings is used. Investment casting is used to fabricate a core of high-strength Aermet. It is shown that it is necessary to open the slots of the magnetic core of the motor in order to make effective use of investment casting and to ease assembly. The effect on motor performance of changing materials and opening slots is analyzed. The squirrel cage, impellers and shaft can be manually assembled to the core. The assembly is then joined using a diffusion bonding process. The feasibility of a Cr-Cu/Aermet diffusion bond is experimentally verified. A systematic method of designing and optimizing a manufacturing process is presented. It is based on the experience of designing the process for the rotor. Thesis Supervisor: Jung-Hoon Chun Title: Esther and Harold E. Edgerton Associate Professor of Mechanical Engineering