MODELO DEL MOTOR DE INDUCCIÓN INCLUYENDO EL EFECTO DE EXCENTRICIDAD

Abstract

The induction machine in the motor operation is one of the most used electrical machines in the petroleum, mining and steel industries. For this reason, the necessity of maintaining a continuous operation is indispensable to avoid enormous economic losses. Therefore, online and off-line diagnostic techniques have been developed in order to detect incipient faults in an early stage. A common fault which is presented in this type of rotating machines is the eccentricity, and it is mainly caused by wear and failure of bearings, unbalance of the rotor or misalignment. Besides, if eccentricity is not diagnosed properly it can cause several failures such as friction between stator and rotor, and as a consequence the destruction of the machine. In this work, an analysis considering the effect of eccentricity in the machine inductances is done as well as the impact on its dynamic behavior under no-load starting performance and during a 3-phase fault at the machine terminals. Mathematical models in different reference frames are presented. The induction machine abc reference frame model is used since it takes into account the inductances rotor position dependence. Also, the modified machine technique is proposed to include the external impedance in the induction motor model and the Winding Function Method is employed to calculate these inductances. In order to consider the effects of different sorts of eccentricity, an expression for the air gap distribution is used, which can include static, dynamic and the combination of both eccentricities. A program in Fortran 90 is developed to simulate the dynamic of the machine taking into account the different conditions mentioned above.