SIMULATION-BASED DESIGN METHOD OF ACTIVE MAGNETIC BEARINGS ACCORDING TOTHE CRITERION OF DYNAMIC STIFFNESS (DDS)

摘要

Applications of magnetically supported rotating machineryare expected to prove, that real loads can be controlledreliably by active magnetic bearings (AMB) during normaloperation and disturbances. The basis for the optimal designis firstly the knowledge about the rotor dynamic behaviorduring operation and secondly the specific load acting onthe rotor. Thereby, static and dynamic shares as well astheir superpositions must be considered, and also specificprocess demands (accuracy of rotor position, maximumallowable rotor displacement).Up to now it has ben usual to design active magneticbearings on the basis of the maximum static load, expectedfrom the application. Often, the dynamic stiffness (asfrequency-dependent ratio between disturbance input forceand output displacement) is considered only during thestart-up phase. At that time the used controller and poweramplifier are already determined. Adjustments are merelypossible in the setting range of the controller. The tuningof the loop components are not always optimal. In addition,the expenditures for start-up increase.The paper describes a simulation-based method for theAMB Design on the parameter Dynamic Stiffness (DDS).The method is also applicable to the theoretical proof ofthe reliability performance during normal operation anddisturbances.The simulation tool MLDyn was developed by IPM. Thedynamic stiffness is determined as a function of thefrequency of the real disturbance forces. A necessarydynamic stiffness is introduced as a criterion for thereliability performance and an allowable shaft displacementas the weighting criterion. The proposed DDS method ispresented for a process pump in a power plant.