Mathematical sizing and design analysis of permanent magnet vernier machine for contra-rotating wind power applications

Over the years, wind energy technology has vividly made progress, as it is economical and cleaner against fossil-fuel alternatives. With the rapid upsurge in turbine ratings up to the MW-power generation level, an unceasing effort is crucial to increase the torque/power density and power factor of the wind-powered machines. Amongst wind-powered machines, the permanent magnet vernier machine (PMVM) is renowned for its high torque density. This paper discusses the detailed design flow of a novel contra-rotating PMVM including sizing equation, geometric relationships, and FEA-based electromagnetic performance analysis compared to the conventional PMVM. The proposed contra-rotating PMVM is analysed with two different winding configurations that is, first with crossed-toroidal and later with concentrated winding configuration, and a comprehensive comparative analysis is made between proposed and conventional PMVM topologies. The contra-rotation of rotors provides more torque/power than the co-rotation within the given machine's size. This comparative analysis provides noteworthy insights into the superior performance of the proposed contra-rotating PMVM topologies regarding torque/power, power factor, and efficiency. A superior torque/power of value 538.23 Nm/1.6 kW is achieved in the case of the design with crossed-toroidal winding configuration with an efficiency of 97.82% whereas, a high-power factor of 0.98 with an efficiency of 91.36% is achieved in the case of the design with concentrated winding configuration.