Measurement and modeling of temperature effects on magnetic property of non-oriented silicon steel lamination

Abstract

Non-oriented Silicon Steel is widely utilized as main core materials for electromechanical equipment, such as motors and generators used in civil power system, because of their attractive characteristics of high magnetic saturation point, good mechanical strength, little anisotropy, and low cost . But in the special cases of modern all electric ship (AES) [1], due to strict requirement on weight and volume, naval-based electromechanical devices are usually smaller than land-based ones . The increase of power density leads to high loss density, thus higher Celsius degrees in the iron core . On the other hand, few silicon steel manufacturer provides magnetic property with other temperatures except room temperature . A lack of coupled magnetic data of non-oriented silicon steel couldn't provide finite element method (FEM) software with reliable input, this fact may prevent researchers from precisely designing and analyzing high power density motor even though advanced analysis and optimization algorithm is adopted . A few papers focused on soft ferrites addressed this issue [2][3][4], literature [5] and [6] measured the thermal effect on magnetic property of silicon steel with the temperature up to Curie point, and the result shows a significant difference with the property we have observed in the ordinary condition . This paper aims to clearly quantify the thermal effect on magnetization and iron loss component, finally propose a temperature-dependent model based on loss separation theory . Considering local temperature where naval motor (high speed generator, propulsion motor) core operates may reach 200 . We customize a special Epstein frame for examining thermal effect on magnetic property of silicon steel, whose size is consistent with IEC and Chinese GB standard, but winding and insulation system can endure -20~200, illustrated in Fig . 1(a) . The size of specimen mentioned in this paper is 300mm length by 30mm width . Take non-oriented silicon steel 50DW465 as example, we maintained the heating oven operating at 26, 50, 100, 150, 200, respectively, then measured magnetization and iron loss performance . Fig . 1(b) shows that magnetization curve varies little with temperature . Iron loss of specimen at various temperature and various frequency (50, 100, 200 and 400Hz) is shown in Fig . 2, which shows that iron loss decreases with rising temperature, furthermore, the higher frequency is, the more sharply the iron loss decreases . When temperature reaches 200, iron loss P B>1 .0T,f=400Hz decrease rate exceeds 20% compared with that in room temperature 26, when B=1 .56T, iron loss decreases by 25% . According to original loss separation theory [7,8], iron loss is divided into static hysteresis, classical eddy current and excess loss . In this paper, we choose to combine the eddy current and excess loss into comprehensive eddy current loss for the same reason with literature [9] . To find out root cause of iron loss's decrease with rising temperature, we have studied the temperature dependence on each of loss com...

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