Axial active magnetic bearing design

The purpose of this paper is to propose a useful method to implement active magnetic bearings (AMBs) on an existing rotating shaft which rotates on conventional bearings. This is feasible if AMBs can produce the same reaction loads of conventional ones and if the size of the vane is large enough to host an AMB. As this substitution could give some difficulties due to the different size between magnetic bearings and conventional ones, a set of equations are performed to show that a variation of some parameters can solve this problem. The coil ratio is the geometrical parameter introduced to develop the present analysis. The variation of coil ratio does not produce a variation of the pole’s surface so that the reaction load does not change. The results are analyzed by numerical analysis by mathematical relationships involving the design parameters, magneto-static simulations and dynamic simulation on the shaft when it is tested by a step response and performing frequency response parameterized with coil ratio. Results show that the displacement carried out by the step response is always the same, when the journal ratio and frequency response are varied, confirming that the reaction load, produced by pole expansion, remains the same when the coil ratio varies. The simulations and results are performed by finite element method magnetic and MATLab software.