Finite-element analysis of electrical machines for sensorless drives with signal injection

A challenge during the design process of an electrical machine is the characterization of the various parameters in a computational time as short as possible. To this purpose, the analysis strategies are manifold. In addition, it is more frequent to obtain parameters of the electrical machine that are necessary for the drive control. In this paper, a strategy to compute the high-frequency signal injection response of an electrical machine adopted in a sensorless electric drive is presented. It allows to determine the self-sensing capability of the machine directly during the design process. Such a capability is defined in any given operating points (for instance along the maximum torque per Amps trajectory). In addition, the computational time required to get such data is very short. After a magnetostatic field analysis, carried out so as to get the torque for a given current, the flux density distribution is stored and the differential reluctivity is evaluated in each element of the mesh. Then, a time-harmonic analysis is carried out in a linearized structure so as to compute the d-q parameters at the injection frequency. The proposed procedure is applied to different type of machines and validated by comparison with experimental results.