What is considered "low frequency" for EM LF Simulations?

Hi, I'm wondering how low the frequency has to be to be considered "low frequency" in the EM LF Electro Simulations. At what frequency level (eg 1kHz, 10kHz, 100kHz, 1MHz?) does it become unreliable and we should use the EM FDTD instead? Is there a method for proving that a certain frequency is within the LF range (as justification for why this type of simulation was chosen)? Thanks! 🙂

See the Sim4Life Manual (2.6.1 EM LF - Simulation Theory)


The quasi-static conditions are sufficient conditions for the quasi-static approximation to hold. In practice, there are cases where the quasi-static approximation still yields accurate results even when the quasi-static conditions are not satisfied. The guideline for this type of cases is to compare to results from full-wave simulations.

A table of the quasi-static approximation criteria for every simulation is written in the log file:
Solid settings: frequency = x Hz, characteristic length (worst case domain diagonal) x
Epsilon Mu SigmaE QS Approx. Quality Static Magn. Field SigmaE/wEpsilon Solid name
The column QS Approx. Quality and Static Magn. Field refers to quasi-static conditions. The column SigmaE/w
Epsilon indicates whether the displacement current ( ≪1 ) or the ohmic current dominates ( ≫1 ). Choosing the Appropriate Low Frequency Solver has further details