Vector control of unbalanced 3-phase IM using forward and backward components

In some industries, continuous operation of 3-phase induction motors (IMs) even under faults until the scheduled maintenance time is essential. Conventional control techniques such as field-oriented control (FOC) cannot be used to control faulty IMs since this will result in significant oscillations in the speed and torque. Consequently, a new control approach must be developed for improving IM performance during fault conditions. This paper presents a method for vector control of 3-phase IMs under open-phase faults. The main advantage of this control scheme is its ability to handle not only one phase but also two phases of open-phase fault conditions. When applying this control technique to a faulty machine, only minor changes to the parameters used in the equations are needed and the conventional FOC algorithm used for healthy 3-phase IMs can still be used. In this paper, simulation and experimental results are presented to study the effectiveness of the proposed technique to control both healthy and faulty 3-phase IMs. The results show that the proposed technique reduces electromagnetic torque pulsations during open-phase fault conditions.