Open-Circuit Fault-Tolerant Control Strategy of Five-Leg Drive in Active Magnetic Bearing

Active Magnetic Bearing (AMB) is widely used in high-speed rotating machinery, which has high requirements for safety and reliability. Power electronic drive working with high voltage/current stress in switching mode is one of the most vulnerable parts of the AMB system. This article proposed a strategy that can achieve the open-circuit fault tolerance for AMB drive, including fault detection, fault location and fault tolerant mode switching for a novel five-leg drive. This strategy ensures that the magnetic bearing rotor maintains stable suspension when failure happens, making the whole system without stopping operation. Firstly, the control method of the five-leg drive and the fault-tolerant mode are proposed. The nature of AMB force makes the reversed current suspension to be possible in backup mode. Then, the failure characteristics are analyzed to develop fault detection strategies. Once the device's open circuit fault happens, the controller will quickly detect the failure and switch the AMB to backup mode. Results of simulation and experiments show the effectiveness of fault tolerance by the proposed fault-tolerant strategy.