This paper presents the operating characteristics of surface-mounted permanent magnet synchronous machine taking into account the influence of stator resistance and inductance variation at high frequencies, whose effect are always neglected in the previous research papers which deal with the operating limits during the flux weakening. First, the machine dynamic equations in d-q reference frame considering the effect of high operating frequency on stator resistance and inductance is discussed based on experimental data. Then, the stator voltage constraint is deduced in the current plane as a function of the stator resistance to study the influence of parameters variation on the operating characteristics. Finally, results are compared with the case of neglecting the resistance and inductance variation at high frequencies.