Distribution on localized two‐dimensional magnetic properties of three‐phase induction motor core

Improving material characteristics and optimizing technical designs have been studied from the standpoint of efficiency improvement of electrical machinery and apparatus. Unfortunately, the local magnetic properties in actual cores are still not understood fully. On the other hand, there is understanding of the two‐dimensional magnetic property, that is, the relationship between the magnetic field strength vector H and the magnetic flux density vector B , which are not usually parallel but have a phase angle. Therefore, local magnetic properties in an actual constructed core should be measured as a vector relation. This paper presents the local magnetic properties in a three‐phase induction motor model core, which are measured with a two‐dimensional measurement sensor. © 2000 Scripta Technica, Electr Eng Jpn, 133(4): 34–40, 2000     

Spiral core made of grain-oriented electrical steel sheet

Spiral cores made of grain-oriented electrical steel sheets (GO) were developed to be used as a high performance motor core. All teeth directions are coincident with the GO rolling directions (easy magnetization axis) in the spiral cores. The GO spiral cores have excellent properties because the GO has very low iron loss and very high permeability in the rolling direction. In the GO spiral cores, the iron losses decrease to a quarter and the inductions are 0.2 T higher at 800 A/m as compared with conventional spiral cores made usually of SPCC. Because the thickness of conventional spiral cores generally varies, applications are limited to automobile alternator cores. The thickness of GO spiral cores changes little during a spiral deformation because the core sheets are deformed transversely to the rolling direction of GO, that is, <110>{011}; the <110>{011} deformation of Fe does not create sheet thickness. As the stiffness and packing factor of a GO spiral core are high in the order of no thickness change, GO spiral cores have high performance for motor cores. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (3): 58–66, 1997     

Phase Correction for High Precision Measurement of Iron Loss Using H‐coil Method

The accurate magnetic properties of electrical steel sheets are important for the development of high‐efficiency electromagnetic devices. In particular, the H‐coil method is a useful technique for accurately measuring magnetic field strength in a single sheet tester. Therefore, we developed a tester for magnetic field properties using the H‐coil method, referred to as the stress load type single sheet tester (S‐SST), and a problem was found in iron loss measurement at a high flux density of 1.6 T or more. In this paper, it is shown that the cause of this problem is the phase difference between the induced voltage in the H‐coil and the B‐coil. Because the phase difference makes the B–H loop slightly twisted near the tip point, the iron losses are evaluated low. Thus, we propose a method of determining the phase correction values. These values are measured in the absence of a specimen in the S‐SST measurement system, and the phase correction method for induced voltage in a coil is investigated. Finally, ideal results for the correction of iron loss in nonoriented electrical steel sheets are shown. The proposed method is effective for the calibration of a single sheet tester using the H‐coil method.     

Calculation of iron loss in rotating machines by direct consideration of eddy currents in electrical steel sheets

A method for calculation of iron loss in rotating machines is proposed. The calculation employs the finite element method while taking into consideration the eddy currents in electrical steel sheets. First, the electromagnetic field distribution and iron loss of several types of electrical steel sheets are calculated by the proposed method, formulated as a one‐dimensional model. The results are compared with those of experiments and the conventional method in order to verify the validity of the proposed method. The influence of the skin effect and magnetic saturation in the electrical steel sheets on the iron loss characteristics is also investigated. Next, the proposed method formulated as a three‐dimensional model is applied to several types of rotating machines. It is shown that the skin effect is significant in the case of high‐frequency harmonic fields and that direct consideration of eddy currents by the finite element method is indispensable in such cases. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(3): 69–80, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21053     

Effects of silicon content,thickness and heat treatment on iron loss properties of high silicon electrical steel sheets

The magnetic properties of high-silicon steel sheets ranging in thickness from 0.35 to 0.03 mm and silicon content from 3 to 7.5 percent is investigated. The minimum iron losses are obtained with the silicon higher than 6.5 percent at the high-frequency range over 30 kHz. The sheet thickness dependency index m is estimated. The heat treatment effects to soft magnetic properties also are studied.     

考虑谐波及集肤效应的电工钢片旋转异常损耗计算与测量

为了准确计算电工钢片的旋转异常损耗,根据谐波分析原理对建立的电工钢叠片有限元模型进行时步有限元仿真;基于旋转铁心损耗计算模型,通过考虑涡流集肤效应对旋转损耗系数的影响结合钢片在中低频率下的损耗测试获得叠片损耗计算的关键系数,间接求得电工钢片中旋转异常损耗的计算式。利用构建的新型三维磁特性测试系统对典型电工钢叠片样品进行椭圆形旋转与交变励磁方式下的宽频铁耗实验测量,并定量地进行了对比与分析。结果表明:2种励磁方式下叠片损耗的变化规律相类似,但其椭圆形旋转各损耗都要比交变时的对应损耗大,必须认真考虑谐波、集肤效应和旋转励磁等对材料特性的影响;所计算出的旋转异常损耗也是相对较小,在1 k Hz时也未占到旋转总铁耗的5%。从而验证了所推导出的计算式和测量手段的正确性与可行性。     

Measurement of the magnetic characteristics of oriented silicon steel in an arbitrary direction

The measurement method and the experimental results on the magnetic characteristics of oriented silicon steel in any direction are described in this paper. A single sheet tester of rotational loss has been used in order to simulate conditions existing in real devices. The flux of any direction is induced in the specimen by exciting from X and Y directions in the same phase. The flux density was measured by each search coil. The magnetizing force was measured by the double H-coil method. The outputs of the B-coils and the H-coils were treated by sending the outputs from the wave digitizer to the personal computer. The components of the magnetic characteristics in the X and Y directions for small values of B are the same. Only the saturation value changes, and it depends on the direction of flux.     

Analysis of electric field induced by ELF magnetic field utilizing fast‐multipole surface‐charge simulation method for voxel data

This paper presents a fast‐multipole surface‐charge‐simulation method for calculating three‐dimensional Laplacian fields in voxel models. This method treats a surface of a voxel that has different inside and outside conductivities as a surface element of the indirect BEM (boundary element method). The main features of the proposed method are as follows. (1) An O(D²) performance in the memory capacity and operation cost is provided by applying the diagonal form fast multipole method (FMM), when the number of voxels is about D³. (2) The boundary matching is imposed by the continuity of the total flux passing through each element, which guarantees the solution globally satisfying Gauss's law; therefore the solution is globally stabilized. This method is successfully applied to calculate the electric field induced by an applied homogeneous ELF (extremely low frequency) magnetic field in a human head model that has 1 mm ×1 mm 1 mm voxel size. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(4): 1–10, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20529     

Low‐resistive and transparent AZO films prepared by PLD in magnetic field

Al₂O₃‐doped ZnO (AZO) thin films have been deposited onto glass substrates using a split target consisting of AZO (1 wt%) and AZO (2 wt%) by pulsed laser deposition with an ArF excimer laser (λ = 193 nm, 15 mJ, 10 Hz, 0.75 J/cm²). By applying a magnetic field perpendicular to the plume, the lowest resistivity of 8.54 × 10^?5Ω·cm and an average transmittance exceeding 91% over the visible range were obtained at a target‐to‐substrate distance of 25 mm for approximately 279‐nm‐thick AZO film (1.8 wt%) grown at a substrate temperature of 230 °C in vacuum. From cross‐sectional TEM observations and the XRD spectrum, a reason why the low resistivity (54 × 10^?5Ω·cm) was reproducibly obtained was considered to be due to the fact that a disorder of crystal growth originating in the vicinity of the interface between the substrate and the film was suppressed by application of the magnetic field and the c‐axis orientation took preference, giving rise to the increase of mobility. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(2): 40–45, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20026     

Formation and properties of nitrogen‐rich phases in austenitic stainless steel by plasma‐based ion implantation

Surface modification of austenitic stainless steel by plasma‐based ion implantation at elevated temperatures below 450°C has been studied experimentally. The nitrogen depth profile at room temperature was similar to that obtained by TRIM code simulation, but the depth of nitrogen penetration increases with target temperature and reaches a few micrometers at a treatment condition of 450°C and an implantation time of 2 h. High‐dose nitrogen implantation exceeding 10¹⁸ cm^?2 at temperatures above 350°C results in the formation of expanded austenite phase (supersaturated f.c.c. phase) with little CrN precipitation, leading to remarkable enhancement of surface hardness without loss of corrosion resistance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(4): 9–16, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10340     

Magnetic characteristics analysis of permanent magnet motor by using complex approximation taking account of two‐dimensional magnetic properties

This paper presents a complex E&S modeling approach, which is developed with a complex approximation for conventional E&S modeling. Complex E&S modeling is used to analyze a permanent magnet motor and the validity of complex E&S modeling is demonstrated. The computation time of complex E&S modeling can be considerably reduced in comparison with conventional E&S modeling. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(2): 9–16, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21268     

Analysis of eddy currents in laminated silicon steel sheets of permanent magnet‐type MRI by 3d finite element method using multinode technique

We developed a method, called the multinode technique, that can take into account any electrical isolation of conductors using the multinodes of the electric scalar potentials. The eddy currents in the laminated silicon steel sheets can be calculated using this method without the mesh of the interlaminar air gap. It is quantitatively clarified that the eddy currents in the laminated silicon steel sheets in a permanent magnet‐type MRI system have effects on the time variations of the flux distributions. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 61–69, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20208