Discussion About the Magnetic Field Produced by Cylindrical Halbach Structures

Abstract

Abstract-This paper uses a three-dimensional analytical approach based on the Coulombian model for studying the magnetic field produced by cylindrical Halbach structures.Such structures, commonly used in magnetic couplings or in electrical machines, are composed of tile permanent magnets with rotating magnetizations. Such assemblies of tile permanent magnets allow one to easily optimize the radial field shape in the air gap of electrical machines. In addition, Halbach structures can be used in magnetic couplings for improving the torque transmitted between the two rotors. Analytical studies dealing with the optimization of such structures generally use a twodimensional analytical approach for calculating either the magnetic field produced by tile permanent magnets or the forces exerted between them. These two-dimensional expressions are useful because they have a very low computational cost. However, their accuracy depends greatly on the structure dimensions. We propose in this paper to use a three-dimensional analytical model based on the Coulombian model for determining the exact shape of the magnetic field produced by a Halbach structure. Such an approach also allows one to determine the demagnetizing magnetic field inside the tile permanent magnets. This element of information is important for the design of tile permanent magnets. In addition, we show that some effects cannot be predicted with the linearized analytical model. This implies that a linearized dimensional optimization is not accurate. This study has been carried out without any simplifying assumptions. Therefore, the calculations of the three magnetic field components are exact for all points in space, whatever the magnet dimensions. We can say that such a three-dimensional analytical approach is a good alternative to a finite element one because it has a lower computational cost and is more accurate.

Magnetic Field in Mri Yokeless Devices: Analytical Approach

“…All these studies deal with the optimization of the static field produced by permanent magnets or currents in coils. In the case of MRI made of permanent magnets, this static magnetic field is generated by tile permanent magnets with uniform polarizations [17,18]. However, most of the studies dealing with the magnetic field produced by MRI structures assume that the magnetic field is produced by a ring permanent magnet with a rotating polarization.…”

Modeling the Dynamic Electromechanical Suspension Behavior of an Electrodynamic Eddy Current Maglev Device

“…The rotation of the magnets can create both a propulsion force in addition to suspension force [4,5]. In order to create a large lift force a flux-focusing Halbach rotor [6][7][8], as shown in Figure 2, can be used.…”

Performances and design of ironless loudspeaker motor structures

“…Many solutions 40 have been imagined and studied to create homogeneous fields in closed cavities or open spaces and we 41 meet here the same problematic [10]- [14]. Some of these structures were also applied to other purposes 42 in electrical machines [15]- [17].…”