Study of the air gap magnetic field distribution of a nuclear magnetic resonance iron-core magnet

Many applications based on iron cores (as for instance electromagnetic actuators) are sized up calculating barely the magnetic force in the air gaps. However other applications exist, more specific, in which not only the flux density amplitude is important, but also the magnetic field distribution. The determination of the magnetic field distribution, based on analytical solutions, can become very complex. On the other hand, available computational tools (as for instance, some based in the finite element analysis) can provide the required results. Furthermore the electromagnetic behaviour, these computational tools allow, in general, to analyse additionally the thermal behaviour of such circuits (approach not followed in this work). In this paper, the generic characterization of the magnetic circuit according to the characteristics of a nuclear magnetic resonance field cycling magnet is done. A classical approach is presented in order to size the major parameters of the magnetic system. The 3D finite element analysis implementation of the magnetic core and the process used to perform the required study are also described. The results obtained are presented and discussed.