Modeling and Control of a Nine-Phase Induction Machine With Open Phases

Multiphase machines have several advantages when compared to three-phase machines. Reliability is one of the most important of those advantages, since the multiphase machine can operate with one or more phases open-circuited. However, the traditional models and control of a balanced induction machine can no longer be used under such open-phase conditions. This paper addresses important issues in the modeling and control of nine-phase induction machines operating under open-phase faults. The development of the proposed model is presented in detail, including an algorithm to guarantee the proper representation of isolated neutral motors. Simulation results illustrate the postfault behavior of the nine-phase motor due to an open phase, including the elimi-nation of torque ripple by applying the proper control methods. Experimental results from a laboratory test setup illustrating the operation of a nine-phase induction motor under one open-phase fault are presented and used to validate the proposed model.