Verification of Load Angle Characteristics of a Novel Counter-Rotating Twin Harmonic PM Machine Using Locked-Rotor Measurements

Recently, three-port machines having one set of electrical connections and two mechanical shafts have received some academic interest due to the possibilities they offer. Using specific magnetic field harmonics, these two shafts can be made to counter-rotate. Counter-rotating turbines can, for example, be used in applications such as low-pressure hydropower pumps, in aviation propulsion using counter-rotating propellers, or similarly in marine propulsion, where they can improve the system efficiency compared to one turbine. Additionally, using a three-port machine can improve the economical feasibility of such applications by only requiring one stator and one power electronic converter compared to using two traditional two-port machines. In this paper, a 2 kW three-port machine with counter-rotating shafts is presented. First, its load angle characteristics are described using analytical equations only. Then, FEA models of the three-port machine are presented, and a numerical locked rotor test is performed to describe the load angle characteristics. Finally, measurements from locked rotor tests on a lab setup are presented. It can be concluded that these three methods produce similar results, verifying that the technology demonstrator can indeed be accurately modeled by two 2D numerical models.