High-speed IPM motors for traction application

Wrapped interior permanent magnet (IPM) synchronous motors represent a recent breakthrough in the domain of high-speed IPM machines. This innovative rotor design, pioneered by Tesla, Inc. in the Model S Plaid electric vehicle, introduces buried permanent magnets (PMs) and a carbon-fiber (CF) sleeve to secure the magnets against centrifugal forces, obviating the need for traditional iron bridges typical in conventional IPM rotor configurations. Inspired by surface-mounted PM (SPM) rotors, this wrapping technique has the potential to transcend existing speed limitations, as Tesla attests to achieving speeds surpassing 20,000 RPM with this cutting-edge motor. Nevertheless, the design and analysis of retaining sleeves are essential for enabling safe and efficient high-speed operation. This thesis embarks on a multifaceted exploration. Firstly, it delves into a comprehensive analysis of the advantages associated with employing high-speed electric motors in powertrains, endeavoring to substantiate the pursuit of elevated rotational speeds. Following an overview of conventional technologies, the thesis scrutinizes the benefits of the wrapped rotor design, unveiling its practical advantages. Secondly, the thesis meticulously formalizes and parametrizes the rotor design. Employing an analytical model for the retaining sleeve, already validated in the literature through finite element analysis (FEA), the thesis introduces a pre-design tool for forecasting the dimensions and characteristics requisite for the carbon sleeve to facilitate motor operation at specific speeds. A comparative analysis is then conducted with the Model 3 IPM motor, which employs iron ribs for rotor retention, to investigate disparities in performance and efficiency. Finally, an attempt is made to establish a scaling law for sleeves and ribs. The fruits of this research effort are envisioned to be seamlessly integrated into the open-source motor design and simulation tool, SyR-e. Within this thesis, SyR-e serves as an essential platform for executing comparative performance analysis between the wrapped IPM motor and traditional designs, offering invaluable insights into the real-world potential of this high-speed motor in various applications. This work has the the aim of helping the continuous evolution of advanced electric motor technology, particularly within the sphere of high-speed traction applications.