This paper investigates the influence of the rotor structure on torque and flux weakening region of V-shape IPM (interior permanent magnet) machine from TOYOTA PRIUS type. More specifically, always keeping the same magnet volume, the effect of the open angle between the two magnet segments of each V-shape pole on the machine performance is studied. Moreover, in order to examine the impact of phase number on the machine characteristics, PRIUS structure is transformed into 5-phase machine of the same type and dimensions. As well, an optimization procedure is carried out to determine the optimal open angle according to main characteristics. The previous investigation is done by using a free FEM (finite elements methods) program coupled with another optimization program. Using this obtained methodology, the study analyzes for 3-phase and 5-phase machine the average and pulsation of torque, cogging torque, phase EMF (electro-motive force), constant power operating capability.