Diagnosis of stator, rotor and airgap eccentricity faults in three-phase induction motors based on the multiple reference frames theory

This paper describes the use of multiple reference frames for the diagnosis of stator, rotor, and eccentricity faults in line-fed and direct torque controlled (DTC) inverter-fed induction motors. The use of this new technique, which was proposed by the authors for the diagnosis of inter-turn short circuits, is extended for the detection and classification of different types of faults. Each fault causes a different disturbance or introduces different components in the motor supply currents. Based on the multiple reference frames theory, by choosing a proper reference frame, it is possible to transform each one of these current components to a d-q frame. In these d-q reference frames, those current harmonics will appear as constants, thus being easily measured, extracted or manipulated. Because each fault causes a different disturbance, the multiple reference frames technique can easily discriminate between different faults. Simulation and experimental results demonstrate the effectiveness of the proposed technique for the diagnosis of stator, rotor, and airgap eccentricity faults in three-phase induction motors. Moreover, due to the operating philosophy of the multiple reference frames technique, its integration into the control system of a DTC induction motor drive is a straightforward task and is briefly addressed at the end of the paper.