The paper discusses the methods for calculating the power parameters of a line start permanent magnet synchronous motor (LSPMSM). The calculations have been performed using the author’s specialized FEM software and professional FEM packages, ANSYS Maxwell and COMSOL Multiphysics. The author’s algorithm for solving equations of the electromagnetic field based on the FEM has been presented. The in-house software developed on this algorithm and professional software have been used to analyse the power parameters of the LSPMS motor. In addition, both calculation time and accuracy were analysed. The calculation results were compared to the measurement results.