An applied control of PMSM is the flux weakening operation for extending the region over nominal speed on nominal voltage. This paper deals with these questions and its impacts. The proved method increases the torque angle and with this the d axis directed component of the stator current vector for reduce the main flux, but the loss developing in magnets became significant. These impacts and its reduction need several investigations. Our work indicates the possibilities and limits of flux-weakening for a given PMSM, and a usable control strategy.