Radial Force Minimization Control for Fault Tolerant Switched Reluctance Machines with Distributed Inverters

Switched reluctance machines (SRMs) are known for their simple and robust mechanical design, low magnetic pole, and phase coupling as well as low short-circuit current and open-circuit voltage during a fault condition. These advantages make the SRM a suitable candidate for applications, which requires high-reliability and fault-tolerant operation. This article addresses the challenge of minimizing the unbalanced magnetic pull (UMP) caused during a single-pole failure, which is the most common electrical fault found in SRMs. In fault-tolerant SRMs, usually, the entire faulty phase is turned off to continue operation. To minimize the loss of torque production during a fault, a distributed inverter (one inverter module per coil) is introduced enabling the SRM to continue operation with all remaining healthy poles. Furthermore, a fault-tolerant control strategy utilizing the advantages of the distributed inverter, namely, radial force minimization control (RFMC), is proposed. This control allows a considerable reduction in the UMP while maintaining constant torque control during faulty operation. A four-phase 1-kW 16/12 SRM with a distributed inverter is used to present the theoretical approach and simulation results of the proposed control algorithm. Furthermore, experimental measurement results for the RFMC are shown to validate the effectiveness of the introduced algorithm.