Analysis of a Current Biased Eight Pole Radial Active Magnetic Bearing Regarding Self-Sensing

In this work a current biased radial active magnetic bearing is investigated with regard to a possible self-sensing operation. The bearing is designed by the help of finite element methods. The force characteristic is investigated and bearing parameters are identified by simulation. Additionally, the position dependency of the coil inductances is evaluated which is the basis for self-sensing. The fundamental principle of the rotor position determination based on current slopes by using the differential open loop transformers approach is presented. Further, simulations are performed to analyze AMB current signals with regard to the rotor position. Finally, experimental tests with an AMB prototype are shown to verify the theoretical analysis. The measured rotor position at constant eccentricity confirms the functionality and represents the starting point for a future implementation of the self-sensing control to the prototype and detailed analysis of the self-sensing performance.