Continuidade de operação de acionamentos multifásicos frente afalhas de circuito aberto

Abstract

Multiphase machines have several advantages when compared to their three-phase counterparts and are attractive for some applications. Fault-tolerance is one of the most important of those advantages, since interruption of service can be costly and dangerous. Faults commonly occur in inverter switches and stator windings. However, a great advantage of multiphase induction machines is the capability to start and keep working even with one or several of its many stator phases open or short circuited. The purpose of this dissertation is to analyze the post fault operation of a nine-phase induction machine under several fault conditions in the machine itself, its terminals and in the inverter switches. Initially, an embrancing literature review is realized. Two methods are developed here to eliminate the torque pulsation which appears in the situation of one or more open phases by maintaining the same balanced magnetomotive force. The first method provides the lowest stator copper losses. The second one produces the same current magnitudes for all the remaining phases. Both methods exempt extra connections or equipment. A model of the nine-phase induction machine with multiple open phases was also developed here. With this model, the speed, flux linkage and torque pulsations can be analyzed when some phases are opened. This model can also be used to validate the proposed methods. The new stationary reference frame stator currents can be calculated to overcome the torque pulsation, with up to 7 open phases. Simulation results show the elimination of torque pulsation by applying the proposed methods, when the machine has an open phase. Experimental results, comparisons and analysis of several types of inverter and machine faults are performed: one, two and three adjacent open phases, phase-neutral fault, phase-phase fault and IGBT short-circuit. Experimental results are included as a support for further work on multiphase induction motor drives modeling and validation.