Due to present-day challenges for the improvement of the operating characteristics of rotating electrical machines, the core material is regarded as increasingly important. Non-oriented (NO) electrical steel sheets are conventionally used for the construction of magnetic cores of rotating electrical machines. The most appropriate choice of material and machine design is based on standardized material data obtained from Epstein frames or single sheet testers. Both, low losses as well as good magnetizability in any spatial direction of the sheet plane are requested. Despite their name, NO electrical steels do show a magnetic anisotropy. A significant increase of loss and decrease of permeability can additionally be induced by mechanical cutting processes to shape the magnetic circuit. Magnetic anisotropy and induced mechanical stress can affect the local iron-loss distribution, magnetizability, acoustic behavior and therefore, have to be considered in numerical simulations of electrical machines. In this paper, the interdependency of the magnetic anisotropy with the effect of cutting is studied in order to improve the necessary understanding of the material behavior.
Słowa kluczowe: electrical steel, magnetic anisotropy, cutting effect.
I. W procesie mechanicznego cięcia blchy elektrotechnicznej mogą ulec degradacji podstawowe jej parametry – straty I przenikalność. Indukowane w procesie cięcia naprężenia wpływają na anizotropię I rozkład strumienia. W artykule W artykule analizowany jest wpływ procesu cięcia na właściwości niezorientowanych blach elektrotechnicznych.
Keywords: blachy elektrotechniczne, anizotropia, cięcie blach, naprężenia mechaniczne
Introduction Machine modeling is the standard tool to design electrical machines. Accurate modeling enables the possibility to achieve high power densities and low losses without unnecessary oversizing, at compact geometries. The potential for improvement by constructive measures is largely exploited and subsequently, the focus for future progress is laid on material design and optimization. In order to incorporate actual material behavior in the design stage of the electrical machines, i.e., during the finiteelement (FE) machine simulations or post-processing, advanced material models have to be developed, which are able to portrait the most relevant occurring effects. These relevant effects include, amongst others, the anisotropy of non-oriented (NO) electrical steels as well as the strong local material deterioration due to mechanical processing. To maximize the energetic efficiency of the electrical machine, iron losses have to be minimized. The mechanical processing of electrical steel components is generally disregarded in machine design, because data from material testing, is standardized for single sheet tester (SST) or Epstein frame (EPF) measurements. In this case gentle processing of samples according to international standards, e.g. IEC60404-3 is required for fixed geometries. However, the geometry and processing majorly affect the properties of the NO in its application and are ideally incorporated already during the design stage . Cutting is highly detrimental to the magnetic properties of the steel sheets, e.g., losses and magnetizability . -2.0 -1.0 0.0 1.0 2.0 -2000 -1000 0 1000 2000 Magnetic polarization J1.5 T, 50 Hz in T Magnetic field strength H in A/m a) Influence of cutting Water jet, uncut Water jet, cut Guillotine, uncut Guillotine, cut 0.0 0.5 1.0 1.5 2.0 1 100 10000 Magnetic polarization Jmax, 50 Hz in T Magnetic field strength Hmax in A/m b) Effect of magnetic anisotr [...]
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