High frequency electromagnetic emissions of cylindrical laminated cores

Abstract

PurposeThis paper aims to propose a high‐frequency (HF) model able to compute the flux density in the vicinity of the laminated stator core of an AC machine.Design/methodology/approachExperiments form the main approach. Analytical results previously obtained with a simplified rectangular laminated structure are confirmed with a standard cylindrical magnetic core.FindingsThree frequency domains are defined, depending on the skin depth relative to the thickness of the magnetic sheets. A methodological approach is proposed for each domain. For higher frequencies, the magnetic core can be considered as transparent for external field computation.Research limitations/implicationsThe HF model is valid for skin depths much lower than the thickness of the magnetic sheets.Practical implicationsThe proposed HF model provides a link between the weak field measured in the natural void existing between the stator core and the housing of large electrical machines. With such a link, it is possible to develop a new monitoring system able to detect and to localize the partial discharges in the stator winding of a large machine.Originality/valueThe low‐frequency limit of the model has been measured. It corresponds to a ratio of 1/40 between the skin depth and the magnetic sheet thickness. Therefore this model offers a new perspective for maintenance applications.