A New Method for RFOC of Induction Motor Under Open-Phase Fault

From an energy conversion point of view, most of electrical machines including Induction Motors (IMs) can be modeled by an equivalent 2-phase machine model (d-q model). A 3-phase IM, with one of the phases opened (faulty 3-phase IM), can also be modeled by an equivalent 2-phase machine. If a conventional Rotor Field-Oriented Control (RFOC) for balanced IM is used for this faulty machine, considerable oscillations in the torque and speed will result. In this paper, a new technique for vector control of faulty 3-phase IM is presented. In the proposed method, the supposition of L-qs/L-ds = (M-q/M-d)(2) = a(2), which is normally applied in other FOC of unbalanced 2-phase IMs, is not used. Results showed that considerable improvements in the torque and speed responses are achieved, specifically in the reduction of the oscillations.