Influence of Aluminum Die-Cast Rotor Porosity on the Effi-ciency of Induction Machines

With the increasing demand for energy efficiency, the international legislative actions are enforcing motor manufacturers to produce motors that meet the mandated efficiency ratings [1], [2]. This makes it crucial to predict the motor efficiency with high accuracy in the design stage. Porosity in aluminum die cast rotors is inevitably introduced during the die casting process and causes the rotor fill factor (FF) to vary from motor to motor for a given design. This causes non-negligible variance in motor performance considering that rotor losses account for up to 20% of induction machine losses. However, the influence of porosity distribution in rotor bars and end rings is not properly considered in existing publications [3]– [5]. This makes it difficult for motor designers to predict the performance of motors accurately to guarantee that they meet the specified efficiency. In this paper, a method based on a combined 2 and 3 dimensional finite element analysis (2D/3D FEA) that takes the porosity level and distribution into account is proposed for accurate prediction of motor performance. The proposed method is verified through FEA and experimental testing.