Model development and synchronous current suppression in active magnetic bearing systems with rotor imbalance

In order to realize model development and synchronous current suppression in active magnetic bearing (AMB) systems with rotor imbalance, a comprehensive model of the AMB system is analyzed, and a suppression method of synchronous current is proposed. First, the way synchronous current, force and torque are induced by both the static and dynamic rotor imbalances through the controller, power amplifier system and motion is described in detail. Next, the model of the AMB system in the four radial freedoms is developed, analyzed and solved. Then, a suppression method based on generalized notch feedback block with a phase shift is proposed to attenuate the synchronous current resulting from the controller, power amplifier system and motion induced voltage. Finally, the validity of the AMB system model and the proposed method are verified through simulation and experiments. The proposed suppression method, which can attenuate the synchronous current caused by the motion induced voltage, is superior to the series method of notch filter and the controller, with a further suppression ratio of 8.8 dB.