Far field extrapolation from near field interactions and shielding influence investigations based on a FE-PEEC coupling method

Abstract

Regarding standards, it is well established that common mode currents are themain source of far field emitted by variable frequency drive (VFD)-cable-motorassociations. These currents are generated by the combination of floating potentials withstray capacitances between these floating potential tracks and the mechanical partsconnected to the earth (the heatsink or cables are usual examples). Nowadays, due tofrequency and power increases, the systematic compliance to EMC (ElectroMagneticCompatibility) becomes increasingly difficult and costly for industrials. As a consequence,there is a well-identified need to investigate practical and low cost solutions to reduce theradiated fields of VFD-cable-motor associations. A well-adapted solution is the shielding ofwound components well known as the major source of near magnetic field. However, thissolution is not convenient, it is expensive and may not be efficient regarding far fieldreduction. Optimizing the components placement could be a better and cheaper solution.As a consequence, dedicated tools have to be developed to efficiently investigate not easycomprehendible phenomena and finally to control EMC disturbances using componentplacement, layout geometry, shielding design if needed. However, none of the modelingmethods usually used in industry complies with large frequency range and far field modelsincluding magnetic materials, multilayer PCBs, and shielding. The contribution of thispaper is to show that alternatives regarding modeling solutions exist and can be used to getin-deep analysis of such complex structures. It is shown in this paper that near fieldinvestigations can give information on far field behavior. It is illustrated by aninvestigation of near field interactions and shielding influence using a FE-PEEC hybridmethod. The test case combining a common mode filter with the floating potentials tracksof an inverter is based on an industrial and commercialized VFD. The near fieldinteractions between the common mode inductance and the tracks with floating potentialsare revealed. Then, the influence of the common mode inductance shielding is analyzed.