Dynamic Mechanism and Active Suppression of Rotor Beat Frequency Vibration in a Magnetic Levitation Induction Machine

Abstract

This study focuses on the phenomenon of rotor beat frequency vibration (BFV) in a 2-pole magnetic levitation induction machine (MLIM), systematically investigating its dynamic mechanisms and subsequently applying an established method for its suppression. First, the BFV synthesis process is described. Subsequently, three primary disturbance sources in the magnetic bearing (MB) system are identified and analyzed, including rotor unbalance, unbalanced magnetic pull (UMP) and magnetostrictive effect. Through numerical solution of a four-degree-of-freedom (4-DOF) rotor dynamic model, the theoretical analysis reveals that MLIM -induced BFV consists of three spectral components: (i) rotor rotational frequency (RRF), (ii) electrical fundamental frequency (EFF), and (iii) the sum of EFF and slip frequency (EFF+SF). Building on these findings, we propose the adoption of a well-established notch filtering technique as an effective means to suppress the BFV. The experimental results confirm the correctness of the analysis of the BFV generation mechanism, and in particular of the EFF disturbance mechanism, and also demonstrate the effectiveness of the vibration suppression method.