High-Speed PM Generators for Organic Rankine Cycle Systems: Reduction of Eddy Current Rotor Losses

In an organic Rankine Cycle system, the permanent magnet (PM) generator is directly coupled to high-speed turbine shaft, to increase system efficiency avoiding the gearbox introduction. Current time harmonics induce high-frequency currents in rotor parts, which cause temperature increase. PMs are strongly affected by the operating temperature, since both remanence and coercive force decrease. This article shows that rotor losses of a high-speed PM generator strongly depend on both winding arrangement and power electronic conversion system connected to the generator itself. Several analyses are carried out to compare different solutions.