Oscillations of rotor supported on magnetic bearings with impacts in retainer bearings

Dynamic properties of a rotor supported on two passive magnetic bearings are investigated by means of the numerical solution to the mathematical model of a prototype developed at the Institute of Thermomechanics ASCR. Magnetic supports always have to include the so-called retainer bearings in order to prevent the rotor from dangerous increase of oscillations due to damage in magnetic bearings. Retainer bearings are rolling bearings, the inner ring of which rotates after an oblique impact by the rotor journal. This rotation introduces an additional degree of freedom to the mathematical model of the rotor support. The main aim of this study is to gain the basic knowledge about the properties of such a system, therefore, a new model of impact motion with large amplitudes, introducing radial Hertz stiffness, material contact damping, tangential dry friction and viscous damping is developed. Dynamic properties of the system described by 6 differential equations containing strongly nonlinear terms are investigated, and the results are presented in form of response curves. Frequency intervals of periodic, quasi-periodic and chaotic motions are ascertained and effects of various parameters on the dynamic behavior of the studied system are determined.