1 Introduction - Finite Element Method Magnetics

If ”parallel” is selected, the current is split between all regions marked with that circuit property
on the basis of impedance ( current is split such that the voltage drop is the same across all sections
connected in parallel). Only solid conductors can be connected in parallel.
If ”series” is selected, the specified current is applied to each block labeled with that circuit
property. In addition, blocks that are labeled with a series circuit property can also be assigned a
number of turns, such that the region is treated as a stranded conductor in which the total current is
the series circuit current times the number of turns in the region. The number of turns for a region
is prescribed as a block label property for the region of interest. All stranded coils must be defined
as series-connected (because each turn is connected together with the other turns in series). Note
that the number of turns assigned to a block label can be either a positive or a negative number. The
sign on the number of turns indicated the direction of current flow associated with a positive-valued
circuit current.
For magnetostatic problems, one could alternatively apply a source current density over the
conductor of interest and achieve similar results. For eddy current problems, however, the “circuit”
properties are much more useful–they allow the user to define the current directly, and they allow
the user to assign a particular connectivity to various regions of the geometry. This information is
used to obtain impedance, flux linkage, etc., in a relatively painless way in the postprocessor.
By applying circuit properties, one can also enforce connectivity in eddy current problems.
By default, all objects in eddy current problems are “shorted together at infinity”–that is, there
is nothing to stop induced currents from returning in other sections of the domain that might not
be intended to be physically connected. By applying a parallel-connected circuit with a zero net
current density constraint to each physical “part” in the geometry, the connectivity of each part is
enforced and all is forced to be conserved inside the part of interest.
The dialog for entering circuit properties is pictured in Figure 15.
3.8 Exterior Region
Figure 15: Circuit Property dialog
One often desires to solve problems on an unbounded domain. Appendix A.3.3 describes an easyto-implement
conformal mapping method for representing an unbounded domain in a 2D planar
finite element analysis. Essentially, one models two disks–one represents the solution region of
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