Double Five-Phase-Four-Leg Topology Converter for Five-Axis Active Magnetic Bearing With Optimized Current Control

Active magnetic bearing (AMB) is a kind of contactless bearing system for high-speed rotational machines. Power electronics converter is the key conversion unit for the electromagnetic force generation. However, there is no such kind of integrated power electronics converter to drive a typical five-axis magnetic bearing by considering the global optimization of power electronics devices. In order to cut the cost and increase the power density of AMB converter, this article analyzes the development status of topology of AMB drive and proposes a novel converter with double five-phase-four-leg topology. The novel converter could control all the ten winding currents of five-axis AMB with only eight switches while the conventional topology needs twenty switches by further utilizing the freedom degree of the AMB control. Also, compared with the conventional topology, the switches of novel topology have same maximum voltage and current. Furthermore, this article proposes the optimized current control methods to minimize the bias current of the active magnetic bearing and applies it to the double five-phase-four-leg topology converter. With the optimized current control, actual current of each coil is decreased and difficulty of thermal design is reduced. The proposed double five-phase-four-leg topology can suspend the five-axis AMB by only using eight switches and eight diodes, which is the minimum compared with the state of the art.