Modeling and Analytical Calculation of a Multiphase Induction Motor in the Phase Loss Asymmetrical Transient Process

The multiphase independent winding induction motor (MIWIM) has wide application in AC drive systems of high control redundancy necessary to ships and coal mines. An accurate analysis of its phase loss transient process is a prerequisite for the phase loss fault-tolerant control. When a phase loss occurs, the internal magnetic fields of the MIWIM are asymmetric. In this case, conventional coordinate transformation or resultant space vector cannot be used to reduce the mathematical model of the motor phase loss to a lower order. Using a five-phase induction motor as an object of study, this paper presents a full-order mathematical model suitable for the asymmetric state in the α–β–z1–z2–z3 coordinate system. The factor analysis of the frequency domain and no consideration of its small value make it possible to reduce the order of the analytical model. According to the constraint relationship between voltage and current, an analytical analysis is made of the motor dynamic characteristics after a phase loss. The results are in agreement with those of numerical simulation and experiment, which verify that the phase loss asymmetric transient model and analytic method of the MIWIM are feasible and effective.