DYNAMIC BEHAVIOR OF ACTIVE MAGNETIC BEARINGS IN PRESENCE OF ANGULAR MISALIGNMENT DEFECT

Abstract

Active magnetic bearings (AMBs) is a device using controlled electromagnetic forces to support a shaft without mechanical contact. One of the primary techniques of condition monitoring of rotors is that of vibration control. Rotating machinery is facing some problems caused by shaft misalignment. This defect leads to a premature failure of the shaft, the coupling and the bearing because of the important vibrations and overloads generated. In this paper, the nonlinear dynamic behavior of a shaft supported by two identical AMBs with eight-pole legs is investigated in the presence of an angular misalignment defect. Thus, the electromagnetic forces, acting on the bearing in horizontal and vertical directions are computed. They are modeled by stiffness and damping matrices. The effects of air gap distance between the stator and the shaft, as well as rotor speed level on the electromagnetic forces are presented. To survey the vibratory response of a misaligned rotor, a numerical simulation of a theoretical model with an angular misalignment defect is studied. All results are presented and discussed in this work.