An Improved Transient Control Strategy for Active Magnetic Bearing Open-Circuit Fault-Tolerant

Active magnetic bearing plays an essential role in high-speed rotational machine. Due to the need for multiple coils, AMB system requires a significant amount of power electronics switches which increases the risk of switch failure. In previous studies, facing switch open-circuit, proper design of redundant devices and implementing current reversal to reconstruct electromagnetic force are necessary. However, fault-tolerant is not only the reconfiguration of circuit, but also the prevention of rotor colliding with the protective bearing. Hence, this paper analyzes the rotor dynamic characteristics during the transient of fault-tolerant. Through the analysis, rotor displacement fluctuation is closely related to the transient time necessary for current reversal. Thus, this article employs DPWM, suitable for multi-axis AMB system, to enhance dynamic response. In the multi-axis system, DPWM can nearly double the rate of current change and markedly reduce transient displacement fluctuations by means of the three-step switch algorithm. A series of fault-tolerant experiments verify the feasibility of the proposed method.