Impact of Magnetic Nonlinearities and Cross-Coupling Effects on Properties of Radial Active Magnetic Bearings

The impact of magnetic nonlinearities and cross-coupling effects on the properties of the discussed radial active magnetic bearings (AMBs) is evaluated in the entire operating range. The characteristics of flux linkages and radial force are all determined by finite element computation, while the current and position dependent partial derivatives of the flux linkages are calculated by analytical derivations of the continuous approximation functions. Calculated current and position-dependent partial derivatives, as well as the radial force characteristics are incorporated into the proposed dynamic AMB model. The results presented show that the magnetic nonlinearities and cross-coupling effects can change the electromotive forces and the radial force considerably. These disturbing effects have been determined and can be incorporated into the real-time realization of nonlinear control in order to achieve cross-coupling compensations.