Efficiency estimation of an air-cored permanent magnet synchronous generator using finite elements and equivalent circuit modelling

The power electronic rectifying stage (DC to AC) in a variable speed generator compromises the generator efficiency and its lifetime. However, this effect in a PMSG might need to be quantified in a design stage for energy output yield calculations. We have conducted an in-depth efficiency analysis of a 20kW direct drive PMSG by the implementation of an equivalent circuit aided by a 2D-Finite Element Model. Copper and core losses due to non-sinusoidal currents have been analyzed when two options of common rectifier topologies are used in the AC to DC power stage: a diode and an active (PWM) rectifier. Simulation results show that the active rectifier does not exhibit a considerable advantage in terms of energy output. So far, for medium-power applications, a diode rectifier can be a cost-effective solution.