A modeling and design method of electrical drive and power converter applied to a powertrain for a heavy duty Series-Parallel Hybrid Electric Vehicle (HEV) is described in this paper. A Surface-Mounted Permanent Magnet Synchronous Motor (SMPMSM) is considered and the motor performances are validated with Finite Element Method (FEM) simulations. Moreover, the authors investigated an optimization strategy focused on multi-criteria optimization, taking into account electrical motor modeling, electromechanical behavior modeling and the overall losses modeling including motor losses and converter losses. The optimization of the powertrain is achieved realizing a compromise between the efficiency and the motor weight minimization.