Comparison of long cable impedances using multiphysics and equivalent circuit models

When a long cable is included in power conversion systems, it causes adverse effects, such as voltage spikes and ringing at load terminals. These nonideal voltages can break the insulation of electric machines, such as transformers and motors, and reduce their lifespan. To estimate such voltage characteristics, cable impedance should be modeled on the basis of the cable length. In this paper, two cable impedance models, a multiphysics model and an equivalent circuit model, are introduced. The multiphysics model using Ansys Q3D Extractor is suggested in consideration of the structure, material, and length of a practical cable. Meanwhile, the equivalent circuit model can be quickly utilized to examine voltage spikes and frequency. The accuracy of the proposed models is verified through simulation and the experimental results based on a motor drive system equipped with 30 and 100-m cables.