A Shared-bridge Converter with Reversed Current Direction for Active Magnetic Bearing Drive

Active magnetic bearing(AMB) is widely used in high speed rotating machinary, and the power electronic converter is a key technology of AMB [1]. A shared-bridge converter has been put forward for multi-axis AMB drive, which can make fully use of devices and reduce the cost [8]. However, the high current rating of shared-phase-leg brings challenge to the devices and the power losses of converter cannot be reduced by this topology. In this paper, a novel topology for AMB drive with reversed current direction is put forward. Comparing with the shared-bridge converter, the novel topology can significantly reduce the current stress of devices on the shared-phase leg by using one more power electronics switch and diode. Meanwhile, the power losses of the converter can be greatly reduced. The principle and the implementation method are introduced and compensation is applied to eliminate the effect of dead-time. Simulation results have successfully validated the feasibility of methods of modulation and dead-time compensation. Suspension and rotating tests have carried out on a 4-axis AMB test rig with the converter of novel topology. The experimental results have verified that the novel converter meets the requirements of AMB drive.