Accurate Coil Voltage Calculation
This functionality improves the accuracy of the computation of the lumped coil voltage in time dependent and frequency domain studies, in 3D, when using the Homogenized multi-turn conductor model. Other lumped parameters computed from the voltage using Ohm’s Law, such as the coil impedance, inductance, and power, also benefit from the improved accuracy. The functionality is enabled by default in time dependent and frequency domain studies, and can be manually controlled using the corresponding check box in the Coil Settings window, Stabilization section. The Stabilization section can be shown by clicking the Show More Options button () and selecting Stabilization in the Show More Options dialog box. It is only available when the Conductor model is set to Homogenized multi-turn.
For domain coils1, the Accurate coil voltage calculation functionality performs a filtering of the external current density applied by the coil to obtain a current density vector field that is numerically divergence free. The filtering is performed by introducing an additional scalar degree of freedom Vf (the filtering variable) and solving the equation
in the coil domain, where Ju is the unfiltered external current density applied by the Coil feature. The filtered current density
is then applied as right-hand side in the magnetic equations. This filtering reduces the spurious electric fields in the solution, in turn improving the accuracy of the induced voltage (which is computed by integrating the electric field in the coil domain).
The filtering equation requires appropriate boundary conditions for the filtering variable, in particular, on the inlet and outlet boundaries of the coil, where the external current density is orthogonal. The approach used to set up these boundary conditions vary according to the coil geometry:
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For Linear and Circular coils, the geometry analysis algorithm automatically detects the inlet/outlet boundaries from the geometry. If this detection fails, use the Override Coil Inlet/Outlet subnode to manually select the inlet/outlet boundaries. Right-click the Coil node to add this subnode.
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For Numeric coils, the subnodes of the Geometry Analysis node are used to identify the inlet/outlet boundaries.
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For User defined coils, use the subfeatures of the User Defined Coil Geometry subnode — Input and Output — to select the coil inlet/outlet boundaries.
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For boundary coils, the filtering turns into a local in-plane 2D formulation. Apart from that, it is mathematically equivalent to the domain coil case.