Design Comparison of Wrapped and non-Wrapped Interior Permanent Magnet Synchronous Machines

Wrapped Interior Permanent Magnet (IPM) synchronous motors represent a recent breakthrough in the domain of high-speed IPM machines. This innovative rotor design 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 or ribs, typical in conventional IPM rotor configurations. Nevertheless, the design and analysis of retaining sleeves are essential for enabling safe and efficient high-speed operation. This paper proposes an analytical model for the retaining sleeve design, introducing a graphical pre-design tool to forecast the dimensions and characteristics requisite for the carbon sleeve, given the target maximum speed. A comparative analysis is then conducted between standard IPM motors with ribs and wrapped IPM motors at different maximum speed speeds, highlighting the benefits of the wrapped IPM design and the possible drawbacks.