In this paper a new complex dynamic model for multi-phase asynchronous motors has been presented using the Power-Oriented Graphs (POG) technique. This new model is obtained using a complex rectangular transformation that reduces the number of the used complex state space variables. The odd harmonic injection has also been considered in order to describe the most general dynamics of the machine by using a compact model. Finally some simulation results have been reported to prove the effectiveness of the new transformation and to show the contribution of the harmonic injection in terms of torque enhancement.