Abstract
Multi-phase machines have several advantages when compared to three-phase machines. Reliability is one of the most important of those advantages since the multi-phase machine can operate with one or more phases open-circuited. However, the traditional models and control of a balanced asynchronous machines can no longer be used under such open-phase conditions. This dissertation addresses important issues in the modelling and control of nine phase asynchronous machines operating under open-phase faults. Finite Element Analysis (FEA) is used in this dissertation to analyse the electromagnetic performance of the nine-phase squirrel cage induction motor (NPSCIM) under healthy and faulty condition. To analyse the dynamic performance of the nine-phase squirrel cage induction motor drive, a set of mathematical equations are established, and validated using Matlab/Simulink. The simulation results illustrate the post fault behaviour of the nine-phase motor due to an open phase without applying remedial strategies. To validate the numerical and computational methods, a testbed has been set up for practical measurements. A customized sensor-less nine-phase voltage source inverter (NPVSI) was constructed. The prototype of the nine-phase induction motor drive was tested for open phase faults (One Open Phase, two Adjacent open phase and two non-adjacent) operations. The results obtained from experimental measurements corroborate with results from numerical and computational method. The results further evidenced the fault tolerance capability of a nine-phase induction motor drive. The latter has positioned itself as strong candidate in applications that require fault tolerance capabilities.