Wpływ efektu zbliżeniowego i naskórkowości na straty mocy w tworniku

W artykule przedstawiono analizę strat mocy w żelazie i miedzi przy zasileniu uzwojenia sygnałem sinusoidalnym o wysokich częstotliwościach. Straty mocy wyznaczone z modelu matematycznego silnika zweryfikowano z pomiarami jakie wykonano na zbudowanym prototypie rdzenia stojana silnika komutatorowego z nawiniętym uzwojeniem. W badaniach uwzględniono wpływ efektu naskórkowości oraz efektu zbliżeniowego na straty mocy w miedzi. Głównym zagadnieniem w pracy było zbadanie wpływu pola magnetycznego połączeń czołowych uzwojeń na straty mocy, poprzez porównanie obliczeń na modelach dwuwymiarowych (2D) i trójwymiarowych (3D) opartych na metodzie elementów skończonych (MES).

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Accurate prediction of power loss distribution within an electrical device is highly desirable as it allows for thermal behavior to be evaluated at the early design stage. This paper focuses on the ac copper loss caused by circulating current effects in electrical machines. Two different phenomena lead to additional ac losses: skin effect and proximity effect. Skin effect is the tendency for high frequency currents to flow on the surface of a conductor and can be mitigated through the use of small conductor strands. The proximity effect is the tendency for current to flow in other undesirable patterns that form localized current loops or concentrated distribution due to the presence of a magnetic field generated by nearby conductors. To evaluate the ac copper loss within the analyzed machine a simplified approach is adopted utilizing the segmented stator topology. To minimize and show an effect of proximity and/or end-winding on the ac copper loss at presented electrical machine a number of winding arrangement are investigated. Three-dimensional and two-dimensional finite element analysis was applied to calculate a ratio of ac to dc resistant at high frequency sinusoidal current. This resistant ratio demonstrates the amount of copper loss which is increased by high frequency. The resistant ratio is strongly dependent on frequency, temperature and shape of slot and size of slot opening. The theoretical finding is compared against the experimental data of total power losses.