A Permanent Magnet Synchronous Motor Model with Core Loss

This paper presents an improved model of permanent magnet synchronous motors (PMSMs) considering core losses. The core losses of a surface mounted PMSM were measured at no-load and load, and the analysis on experimental results shows that the core losses in a PMSM can be attributed to the components produced by the rotor permanent magnets and the stator currents. The conventional equivalent circuit model of PMSM with core loss can account for the former but not the latter, and therefore, an additional core loss resistor is required to account for the additional core loss component due to the armature reaction. The nonlinear resistance for the no-load core loss is explained from the core loss model of magnetic materials. The method to determine these core loss resistances from the no-load and load tests is also presented. The relation between the core loss components and the corresponding resistors is clearly demonstrated by the analysis of experimental results. The permanent magnet synchronous motor (PMSM) can be a serious competitor to the conventional DC and induction motors in servo applications due to its high power density, torque to current ratio, and efficiency. The model of PMSM is concerned by many researchers because it is important in motor performance analysis and drive system design. In addition, the performance of a PMSM drive system is considerably influenced by the accuracy ofthe model. The core loss or iron loss, caused by the permanent magnet (PM) flux and armature reaction flux, is a significant component in the total loss of a PMSM, and thus, it can have a considerable effect on the PMSM modeling and performance prediction. This paper proposes a model of PMSM taking into account the stator core losses. No-load and load tests were carried out to determine the total core and mechanical loss of a PMSM, which was then separated by fitting the experimental results to their physical models. The relationship between the core loss resistor Rcl and the internal voltage Vi is estimated by the curve fitting of the no-load results. With the load test results, the conventional PMSM model is modified by adding an extra resistor, R c2, to account for the effect of armature reaction on the core loss. The values of Rc2 are determined by the