Material properties extraction of the stator core of a 50 kW permanent magnet synchronous machine (PMSM) by means of nondestructive testing method

In this research physical (e.g., density) and mechanical (e.g., Young’s modulus, etc.) properties are extracted via non-destructive testing (NDT) method for the stacked stator core of a 50 kW permanent magnet synchronous motor. Mechanical properties like Young’s modulus, Poisson’s ratio, etc. are essential parameters for the mechanical design of a component. As known, electric motors are comprised of two main parts, namely stator and rotor. In permanent magnet (PM) machines, the rotor of the electric motor includes some permanent magnets instead of windings; but the stator consists of windings to form the magnetic field. The stator core is made of a stack of coated electrical steel sheets or laminations, which are pressed together with tension bolts and tension bars or welded together in some cases. This matter causes different mechanical properties in axial and other directions. For electric machines such as induction and synchronous machines, the stacking pressure determination of the stator core is one of the major steps in machine design. The integrity of the stator core depends on the proper implementation of aforementioned step. The stacking process of the stator core of this type of electric (PM) machine comprises of three main stages including applying the stacking pressure, laminations welding under pressure, and releasing stacking pressure. These steps run as some static processes. In this study, the density and Young’s modulus of the stator core of a certain 50 kW PM electric machine in various directions are extracted using a non-destructive testing method. The non-destructive testing method utilized in this work is experimental modal analysis. Using the natural frequency obtained from modal test as the objective function and implementing the FEM optimization, the material properties are presented.