You can use the SOLID96 element to represent all interior regions of your model: saturable regions, permanent magnet regions, and air (free space). For current-conducting regions, you need to use current source primitives represented by the SOURC36 element. See Modeling Current Conduction Regions for more details.

At the exterior of air elements, use of INFIN47, the four-node boundary element, or INFIN111, the 8- or 20-node boundary element, is recommended. INFIN47 and INFIN111 can model the far-field decay in the magnetic field, and usually give better results than a flux-parallel or flux-normal condition. Of the two elements, the INFIN111 element more accurately models the exterior domain.

When using SOLID5, SOLID96, or SOLID98 elements with SOURC36 elements, the source elements should be placed so that the resulting Hs field fulfills boundary conditions for the total field, that is, the source field created by SOURC36 elements should closely match the boundary conditions on the meshed domain. For example, at unconstrained surfaces of the model where the total field will be parallel, the source field should be approximately parallel.

The phenomenon is similar to the treatment of symmetry conditions. Even if the studied domain is only a fraction of the full size problem, you should extend the SOURC36 geometry to the full model to obtain a good solution.

The default system of units is MKS (meter-kilogram-second). You can change this to any other system you prefer using one of the methods shown below. Once you choose a system of units, all input data must be in that system. For convenience, you may create your geometry in other units (for example, millimeters or inches) and then scale it to the appropriate analysis units.

Based on the input units you specify, the free space permeability  μ_o is determined automatically as follows: