The aim of this project is to study the LEM current transducer LAX 100-NP and to determine its dynamic performance using the finite element software Flux2D/3D. Firstly, the secondary impedance of the transducer is simulated, and the results are compared to the measurements. For Flux3D simulations, according to the strength of the diffusion effect in the magnetic circuit, two formulations are used depending on the frequency.