Direct torque control of three-phase PM brushless AC motor with one phase open-circuit fault

In this paper, direct torque control (DTC) of a three-phase permanent magnet (PM) brushless AC (BLAC) motor having one phase open-circuit fault is described. An extra inverter leg is employed to provide the current path during the fault operation. The new flux estimation algorithm for the faulty motor is presented. The simulation results show that the proposed DTC yields satisfactory torque and flux control. The performance of the developed system is verified by experiments on a prototype system. In addition, the influence of low pass filter, sampling time delay, as well as the unbalanced phase back-emf waveforms is investigated, while the difference in DTC performance between healthy and faulty systems is also discussed and corresponding simulated and measured results presented.