Tolerance Analysis for Electric Machine Design Optimization: Classification, Modeling and Evaluation, and Example

Electric machine design optimization is a popular topic in electrical engineering. Thanks to major accomplishments in Mathematics and Computer Science, nowadays the investigation of thousands of designs for particular optimization tasks is possible. Huge effort is made for developing evermore complex multi-physics simulation models including, e.g., thermal or mechanical aspects besides electromagnetic performance investigation. The impact of tolerances is often disregarded. This paper gives an overview of recent activities in machine design optimization. Consequently, the implementation of tolerance analyses for machine designs is explained. A categorization based on mathematical tolerance representations, typical tolerance-affected parameters and their respective modeling effort, as well as measures for evaluating the impact of tolerances, i.e., the design's robustness, are discussed. An exemplary sensitivity analysis featuring an interior permanent magnet synchronous machine with spoke-type rotor structure is introduced. The performance of two different designs in the presence of uncertainties is investigated. Results reveal the importance of incorporating tolerance analyses to electric machine design optimization.