Modeling and Control of an Axial Magnetic Bearing for a Prototype of Electric Motor Supported by Radial Magnetic Bearings

Research on magnetic bearings is being conducted in universities and research centers all over the world. Among the main advantages of the use of these devices are the reduction of friction losses and their corresponding necessity for maintenance. Magnetic bearings can already be found in rotating machines in medical, food, oil, and military industries. As to electric machines, the use of such electromagnets provides a natural instability to the system. Therefore, controllers become necessary to hold the rotor in an equilibrium position, without contact with the stator. In this work, modeling, implementation, and practical results of an axial position controller is presented. An axial controller has been designed to be implemented on an experimental prototype that consists of an induction motor, arranged in the horizontal position, already supported by radially controlled magnetic bearings. Different from other approaches, the experimental stiffness and damping observed along the axial direction, when only the radial magnetic bearings are acting, was taken into account for the controller design.