Electromagnetic and Structural Trade-Offs of V-Position Magnet Embedding in Outer-Rotor PMSMs

V-position magnet embedding is widely used in interior permanent-magnet synchronous machines (IPM-PMSMs) to improve field-weakening capability, with its design principles largely established for inner-rotor topologies. In outer-rotor permanent magnet synchronous machines, however, magnet embedding directly interacts with rotor structural constraints, fundamentally altering its design implications. This paper investigates the influence of V-position magnet embedding in an outer-rotor PMSM through a controlled study in which a reference surface-magnet design is transformed into a V-position interior-magnet configuration while preserving stator geometry, pole arc, magnet height, and comparable voltage–speed operating conditions. Magnet embedding is parameterized using a geometric variable termed V-depth, defined as the radial distance from the air gap to the magnet edges at the pole center. The results reveal that, in contrast to inner-rotor machines, adjustments to V-depth in outer-rotor PMSMs introduce a pronounced interplay between electromagnetic performance and mechanical constraints. Any increase in magnet embedding depth necessitates corresponding changes in rotor yoke thickness and overall dimensions. This coupling governs not only the achievable torque and field-weakening characteristics, but also introduces tangible trade-offs in structural mass and packaging. Consequently, electromagnetic torque and specific torque follow different trends: while torque may partially recover at larger V-depth values due to increased magnet width, the concurrent increase in structural mass prevents a corresponding recovery in specific torque. These findings demonstrate that magnet embedding in outer-rotor PMSMs cannot be treated as a purely electromagnetic design variable, but must instead be considered as a coupled electromagnetic–structural problem. A moderate V-depth range provides the most favourable compromise between torque capability, mass, and field-weakening performance.