Default Boundary Conditions (Natural and Neumann)

Field behaves as follows:

• Natural boundaries – H is continuous across the boundary.
• Neumann boundaries – H is tangential to the boundary and flux cannot cross it.

Ordinary field behavior. Initially, object interfaces are natural boundaries; outer boundaries and excluded objects are Neumann boundaries.

Zero Tangential H Field

Flux is perpendicular if tangent components are zero or if a zero tangential H-field boundary condition was applied.

External AC magnetic fields.

Tangential H Field

The tangential components of H are set to predefined values.

External AC magnetic fields

Integrated Zero Tangential H Field

For applications such as a motor with the shaft excluded, there remains a hole in the middle. In such cases, on the hole's boundary, neither the Tangential H Field boundary (where integration of the tangential H field is non-zero), nor the Zero Tangential H Field boundary (where the tangential H field is zero everywhere) can be applied because – for the hole boundary case – integration of the tangential H field is zero, but the tangential H field is not zero everywhere. Integrated Zero Tangential H Field can be used for such applications.

Cases such as the boundary around the hole left when a motor's shaft is excluded.

Insulating

Same as Neumann, except that current cannot cross the boundary.

Perfectly insulating sheets between conductors.

Symmetry

Field behaves as follows:

• Odd Symmetry (Flux Tangential) – H is tangential to the boundary; its normal components are zero.
• Even Symmetry (Flux Normal) – H is normal to the boundary; its tangential components are zero.

Planes of geometric and magnetic symmetry.

Matching
(Independent and Dependent)

The H-field on the dependent boundary is forced to match the magnitude and direction (or the negative of the direction) of the H-field on the independent boundary.

Planes of symmetry in periodic structures where H is oblique to the boundary.

Radiation

No restrictions on the field behavior.

Unbounded eddy currents.

Impedance

Includes the effect of induced currents beyond the boundary surface.

Conductors with very small skin depths.

Resistive Sheet

When two conductors are in contact within a conduction path, a voltage drop normally exists across the contact surface due to the imperfection of the contact between the two conductors. This boundary condition assigns a resistive sheet to consider the impact of this kind of voltage drop. The resistive sheet is defined by a lumped resistance in ohms.

Voltage drop and loss on the contact surface between two different objects within a conduction path.

Thin Layer

This boundary creates a field discontinuity between the two sides of the selected surface based on its thickness and the given electric and magnetic material proprieties. When the air gap option is selected, the conductivity is assumed to be zero and the relative magnetic permeability is assumed to be equal to one.

Thin conductors and ferromagnets, and narrow air gaps