Inter-laminar short-circuit faults between the laminations of electrical machines, and other magnetic devices, have been one of the major challenges for the suppliers and customers of electrical steels. Extra power losses caused by inter-laminar faults depend on many factors including the location of the fault points. In this study, fundamental definitions and concepts of inter-laminar short-circuit faults, effect of inter-laminar faults on configuration of the magnetic cores and FEM verification are presented. Experimental works were performed to study the effect of interlaminar faults with different configurations on the total power loss to distinguish and locate the critical and destructive faults. In the relevant studies, artificial short circuits of different configurations were applied between laminations of packs of four Epstein size laminations of 3% grain oriented silicon steel. Extra power losses caused by the inter-laminar faults were measured and the results were analysed.

Cutting and punching of the electrical steel can cause edge burrs which lead to interlaminar short circuits between the laminations. In this paper, based on an equivalent electric circuit of the eddy current path, an analytical method has been developed to estimate the eddy current power loss of the magnetic cores, caused by the interlaminar faults, in a wide range of flux density and magnetizing frequency. Important factors, such as skin effect, nonuniform flux density distribution, complex relative permeability, and the nonlinear relation of , which are often neglected in the literature, are highlighted. Fundamental concepts of the interlaminar fault and its consequences, the effect of interlaminar faults on the configuration of magnetic cores, and finite-element method verification are presented in this Part I paper. Modeling of eddy current, together with experimental results of eddy current measurements of packs of shorted laminations, are reported in Part II. Index Terms-Complex relative permeability, eddy current power loss, edge burr, finite-element method (FEM) modeling, high frequencies, interlaminar fault, skin effect.

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.

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and Fox, David (2013) 'Eddy current loss estimation of edge burr-aected magnetic laminations based on equivalent electrical network-part II: analytical modeling and experimental results.', IEEE transactions on power delivery., 29 (2). pp. 651-659.

This paper investigates the influence of a wide range of magnetising frequency and peak flux density on the magnetic properties of the electrical steels. In the relevant studies some important factors and operational properties, e.g. skin effect, nonuniform flux density distribution, complex relative permeability and magnetisation characteristic of the material, which are often neglected in the literature, are highlighted. Analytical modelling and experimental works were performed for 3 % grain oriented silicon steel. In order to show the impact of peak flux density on the magnetic properties, two peak flux densities 1.3 T as a high permeability point and 1.7 T as a low permeability point were considered. The results highlighted that magnetising frequency and peak flux density are two determinant factors with significant effect on the magnetic properties of electrical steels.

Inter-laminar faults between laminations of the magnetic cores increase core losses and could cause major damage to electrical machines. A system has been developed to detect inter-laminar fault between the laminations of the magnetic cores by means of Flux Injection Probe (FIP). Experimental work was carried out to calibrate the measuring system and qualify its accuracy over a wide measurement range. Application of a prototype FIP to quality assessment of transformer laminations was investigated in two stages: inspection of stack of laminations with known inter-laminar faults applied by artificial shorts and inspection of stack of laminations with unknown quality. The experimental results show that the developed system is capable to detect inter-laminar fault between as few as 2 laminations.

Hamzehbahmani, Hamed (2019) 'Development of a new approach to core quality assessment of modern electrical machines.', IET electric power applications., 13 (6). pp. 750-756.The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.Abstract-Hysteresis behavior of the magnetic materials is an interesting physical concept and has important practical applications in physics and engineering. In this paper a new approach is developed to evaluate the quality of magnetic cores, based on the measured dynamic hysteresis loop. In this study, artificial inter-laminar faults of different configurations were applied on stacks of four standard Epstein size laminations of 3 % grain oriented silicon steel. Dynamic hysteresis loop of the samples were measured and analysed over a range of magnetising frequency and flux density, to calculate the extra power losses caused by the artificial faults. The results shows an accurate evaluation of the extra power loss compare to the bulk measurement, with a maximum difference of less than 4 %.