Model and Control of a Six-Pole Magnetic Bearing

Mechanical Bearings are machine elements that support the rotating axes and promote smooth movement between contact surfaces. In order to eliminate friction between the parts and, consequently, the need for lubrication, Active Magnetic Bearings (AMB) were developed based on the generation of reluctance electromagnetic forces. Due to the unstable nature of this equipment, it is necessary to implement a control strategy to avoid displacements and keep the axis aligned. There are studies about different geometries of magnetic bearings regarding the number of poles they present. The eight and four-pole configurations are the most usual, although other alternatives are being studied, like the three and six-pole geometry. The main objective of this paper is to present a mathematical model for the six-pole magnetic bearing applied to a vertical rotor system, propose control strategies to stabilize the system and compare its performance to the four and eight-pole bearings. In addition, comparisons between rotational speeds are carried out to define low, medium and high rotational ranges, and a study on the system’s response to control designed for a certain rotational speed in the system operating at different speeds.