1 A practical approach to modelling induction machines saturation M.E.H. Benbouzid 1 , M. Zerikat 2 and M.S. Naït-Saïd 3 1 CREA – EA 3299, University of Picardie “Jules Verne”, Amiens, France 2 ENSET, Oran, Algeria 3 University of Batna, Batna, Algeria SUMMARY This paper deals with a new approach for saturated induction machines modelling based on the so-called H-G diagram. This allows the description of the saturation in the machine using only three parameters that are instantaneously determined by a plotted circle (H-G diagram) for each saturation point. Furthermore, this approach can be extended to induction machine modelling taking into account other phenomena such as temperature and skin effects. The proposed approach has been compared to the conventional induction machine modelling with and without cross-saturation. Simulation results have shown that the proposed approach has some advantages over cross-saturation such simplicity and accuracy, especially during the induction machine starting-phase and also when it is sufficiently loaded. KEY WORDS: Induction machine; modelling; saturation; cross-saturation; H-G diagram. 1. INTRODUCTION When induction machine saturation is neglected, especially at rated condition, its transient is erroneously analyzed when using constant Park model parameters. In fact, the machine inductances could widely vary depending on the flux inside the machine, which is greatly depending on the absorbed currents. Therefore, it becomes necessary to use an induction machine nonlinear time-varying inductive parameters model. The induction machine parameters are in this case derived from the magnetization characteristic [1-5]. Moreover, the machine saturation could change very quickly, leading to very quick change of rotor inductance, which could affect the drive dynamic when the induction machine is vector controlled [6-7]. The induction machine model taking into account saturation is represented in the orthogonal d-q axis system. The orthogonal d- and q-axis are greatly coupled by time- varying terms introduced by the saturation effect. The existence of such coupled terms, defining the so-called cross-saturation phenomena, is up to now the subject of a controversy. In fact, some researchers have argued that the presence of cross-saturation in saturated induction machine modelling is the pure consequence of a mathematical derivation [8]. *Correspondance to: M.E.H. Benbouzid, CREA, University of Picardie “Jules Verne” – 7, Rue du Moulin Neuf, 80000 Amiens, France. Phone: +33 3 22 82 76 80, Fax: +33 3 22 82 78 22, E-mail: m.benbouzid@ieee.org.