Abstr-acl: /'I dcsign pnl(;css comprising aspccts of modelling and analysis is dcvcloped, impkmenled and vcrificd for a Ikxihk rotor activc magnctic hcaring systcm. The system is specified to experience the first three critical frequencies up to an operating specd of 10.000 rpm. Rotor stahility at critical frequencics places specil'ic constr,linlS on the equivaknt stillncss and damping p,lrameters of thc active magnctic hcaring. /'In iterative design proccss is Ihen initiated hy an eleetromagnctic design of the r,ldial activc magnetic bearings resulting in paramcters used in the detailed modelling of the systcm. Stiffness and damping parameters as well as system dynamic response arc verified and used to design a Ikxible rotor. The magnctic hearing locations. displacemcnt sensor locations and rotordynamic response arc verified using finite elemel1l analysis. The design of the rotor stands central to thc iterative dcsign process since it impacts on the forces experienccd by the active magnetic hearings as well as thc critical frequencics of the active magnctic bearing system. Once constructed the actual activc magnetic bearing system stillness and damping parameters as well as dynamic rcsponsc arc compared to modelled results. Thc rolOrdynamic response is characterised by measuring thc rotor displacemcnt at pre-dcfincd locations as the rotor traverses the critical frcqucncies. Thesc results arc compared with the predicted rotordynamic responsc.

The object of the author’s experiments and investigations is stated to have been the production of an instrument that would, under all variety of circumstances, give a correct (magnetic) meridian direction, or in some way indicate the amount of its own error; and he considers that he has, at least partially, succeeded in the attainment of this object in the instrument described in this paper, and of which drawings accompany the communication. In order to determine the nature of the action of a mass of iron on a magnetic needle, the author constructed needles with the magnetic bar wholly on one side of the central support, counterpoised by an arm carrying a weight on the other.