The optimal sizing of electrical machines for a given profile is an important issue in automotive industry to reduce volume and so to save scarce material and cost of actuator. Two phenomena limit this volume, i.e. the magnetic saturation and the increase of temperature especially in coils end turns and in permanent magnets. Consequently, an optimal sizing requires the use of multiphysics models, i.e. coupled electromagnetic-thermal. This paper proposes an original method for optimal sizing on a given profile by the use of two models: a fast electromagnetic model where the temperature is indirectly taken into account by the electrical current density in windings. This model is implemented in a SQP optimization method. And a coupled model electromagnetic-thermal model, which provides the time evolution of the temperatures during the given profile inside the machine. This second model, more complex than the previous model requires long time calculation especially for long profile. This article proposes a strategy using the two models in order to reduce the volume of the actuator. The two models will be described and the optimization results will be given and commented.