Comparison of a solid and a laminated rotor for sensorless control of radial active magnetic bearings

This paper presents a method for sensorless control of radial active magnetic bearings. Self-sensing methods are based on position estimation by electrical parameters as current and voltage signals. A novel bearing design which has only three stator coils in star connection for high economic manufacturing and permanent magnet biasing for low operational costs is used. Combining a standard three phase voltage inverter and a sensorless control method a cost-effective magnetic bearing system can be realized. For a general simplification of the system all hardware components will be optimized and therefore also the rotor of an active magnetic bearing usually constructed of laminated steel can be reduced to a solid steel rotor. Hence, the influence of the different rotor types on the presented sensorless position detection method is field of interest of this work. A finite element analyses is used to verify differences between the solid and laminated rotor. The implementation of the sensorless method is described and measurement results are presented. Statistical methods are used for comparison of both rotor types with same geometric properties. Finally a conclusion shows the capability for sensorless control of both rotors in principle.