In order to improve the internal-fault simulation of three-phase induction motors, the authors present the basic idea of the "bidirectional revolving magnetic fields" concept, i.e. each coil carrying AC current will produce a pulsating MMF that can be decomposed into two opposite-directional revolving MMFs. One can then synthesize the effects of all coil MMFs according to actual inner-faults in order to take the place of the symmetrical components method in solving the internal faults of induction motors. In addition, the motor parameters are influenced by internal faults, for example, the slot leakage reactances, even if referred to the same number of turns, are still unequal, and the same is true of the resistances, which have been considered in this paper. On the basis of these ideas, a new mathematical model and a corresponding computation program have been built, and simulation results have also been obtained. The simulation results are quite approximate to the measured data. This analysis method is accurate enough and simpler than other methods, such as the multi-loop method.
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