Symmetric Short-Circuit Model of Synchronous Machines based on Flux and Loss Maps

The peak current during a short-circuit is a crucial performance index for Permanent Magnet Synchronous Motors (PMSMs). This indicator is even more critical for propulsion applications since the Active Short-Circuit (ASC) is one of the most common reaction strategies triggered when a system failure is detected, both for terrestrial and aerospace systems. Because of the non-linear behaviors of high-performance PMSMs and the trend towards rare-earth free Permanent Magnets (PMs) for traction applications, the peak current during ASC must be accurately evaluated, avoiding excessive oversizing but still guaranteeing the health of the PMs after the fault. In this paper, a fast and accurate model to compute the instantaneous current and torque during ASC is presented. The proposal relies on flux and loss maps, directly accounting for saturation and cross-saturation phenomena and also the iron and AC loss, typically neglected in the existing models. The proposed methodology is exploited to assess the performance of a double three-phase PMSM designed for aerospace applications. The two AC loss components, namely iron loss and loss related to skin and proximity effect in the winding, are considered and the effect of each of them is highlighted. Then, the proposed maps elaboration is compared with the dynamic model in Simulink/SimScape and against dedicated Finite Element Analysis (FEA) simulations.