Design and analysis of a blade-embedded limited-angle torque motor for vertical-axis water turbines

Vertical-axis cross-flow tidal turbines suffer from alternating hydrodynamic loads, a consequence of dynamic blade stall. Intracycle blade pitching allows for mitigation of these effects, resulting in increased efficiency and lower structural loads. In this study, two designs for blade-embedded limited-angle torque motors are presented. Geometrical parameters of both structures were discussed for the required output torque and pitch angle range. According to the finite element analysis, the expected design parameters are mainly restricted by the saturation of the primary. Thus, placing the primary in the rotational part of the motor, where more space is available, allows for reaching the design parameters with a significantly reduced current density on the windings. The required induced voltage will be slightly higher for the structure with rotational primary, but shows greater potential in reducing its size due to the lower current density compared to the design with the primary placed in the stator part.