For conductors with high conductivity, the main loss is the ohmic loss. For low-conductivity materials such as insulators, the dielectric losses are usually modeled in the frequency domain. Difference dielectric loss models are available in the Constitutive Relation D-E section of the interface. The frequency domain equations model dielectric losses with the complex permittivity, which is expressed as

where ε' is the real part of εr, and all losses (dielectric and conduction losses) are given by ε''. The dielectric loss model can also single out the losses from finite conductivity (so that ε'' only represents dielectric losses) resulting in:

where tanδ is called the loss tangent.

The frequency domain equations allow for magnetic losses to be introduced as a complex relative permeability.

where μ' is the real part of μr, and all magnetic losses are given by the imaginary part μ''.

The complex relative permeability model is available as one of the Magnetization models in the Constitutive Relation B-H section.