Design and analysis of a toroidal tester for the measurement of core losses under axial compressive stress

Abstract

Electric machine cores are subjected to mechanical stresses due to manufacturing processes. These stresses include radial, circumferential and axial components that may have significant influences on the magnetic properties of the electrical steel and hence, on the output and efficiencies of electrical machines. Previously, most studies of iron losses due to mechanical stress have considered only radial and circumferential components. In this work, an improved toroidal tester has been designed and developed to measure the core losses and the magnetic properties of electrical steel under a compressive axial stress. The shape of the toroidal ring has been verified using 3D stress analysis. Also, 3D electromagnetic simulations show a uniform flux density distribution in the specimen with a variation of 0.03T and a maximum average induction level of 1.5 T. The developed design has been prototyped, and measurements were carried out using a steel sample of grade 35WW300. Measurements show that applying small mechanical stresses normal to the sample thickness rises the delivered core losses, then the losses decrease continuously as the stress increases. However, the drop in core losses at high stresses does not go lower than the free-stress condition. Physical explanations for the observed trend of core losses as a function of stress are provided based on core loss separation to the hysteresis and eddy current loss components. The experimental results show that the effect of axial compressive stress on magnetic properties of electrical steel at high level of inductions becomes less pronounced.

Magnetic Properties of Silicon Steel after Plastic Deformation

“…In order to facilitate useful modelling of these multi-directional effects, equivalent stress models were proposed [ 20 , 21 ]. The effect of compressive stress in the thickness direction was investigated similarily in [ 22 , 23 , 24 ]. Few reports where found by the authors on the effects of plastic deformation after the mechanical load was released.…”

Cross-Linking-Derived Synthesis of Porous CoxNiy/C Nanocomposites for Excellent Electromagnetic Behaviors

“…As already discussed in Figure 6, all three Co x Ni y /C samples possess hysteresis loss 47,48 at the applied field, which is helpful to the enhanced EM wave absorption. Eddy current loss 49,50 occurs in the three Co x Ni y /C composites, especially at high frequency. The developed microcurrent transforms more EM energy to joule heat as well as other forms of energy.…”

Investigation of the compaction process of electrical machines magnetic circuits and its detrimental effect on magnetic performances

“…According to the literature, mechanical stress applied in the plane of electrical steel sheets has a strong influence on their magnetic properties 1 : this can improve or degrade them depending on the nature of the stress (compressive stress or tensile stress), the level of stress and its direction with regard to the magnetic flux direction. However, for mechanical stress applied in the thickness direction of the lamination, few papers are found in the literature and the presented results vary significantly from one study to another 9 – 11 . Obviously, in this direction, one has to only consider compressive stress because tensile stress has no physical application and is against the objective of the compaction process.…”