Three-dimensional Magnetic Properties Research Articles

Modeling and Measurement of Magnetic Hysteresis of Soft Magnetic Composite Materials Under Different Magnetizations

The soft magnetic composite (SMC) materials and their application in electromagnetic devices have undergone significant development due to their unique advantages, such as low eddy-current loss, quasi-isotropy of mechanical and magnetic properties, low cost, and low material consumption during the production process. However, the magnetic properties of the SMC materials are very different from that of the laminated SiFe materials, which are particularly challenging for the design and application of electrical machines. This paper presents the modeling and measurement of magnetic properties of the SMC materials under both alternating and rotational magnetic excitations. Based on the underlying magnetization mechanisms, a vectorial elemental operator with biaxial anisotropy is introduced, and the concept of distribution function is utilized to describe the density of operators in the specimen. To verify this proposed model, the magnetic hysteresis of the SMC material is simulated and compared with the experimental results obtained by the three-dimensional magnetic property measurement system. The good agreement shows the validity and practicability of this vectorial elemental operator.

Measurement of Three-Dimensional Magnetic Properties With Feedback Control and Harmonic Compensation

Three-dimensional (3-D) magnetic fluxes exist in rotating electric machines and T-joints of three-phase power transformers, and may cause local overheating in these devices. In this paper, 3-D magnetic properties of the core materials are measured by an improved 3-D magnetic property tester. First, the 3-D magnetization system is modeled by the voltage and flux linkage equations. Their parameters including the self and mutual inductances and nonlinear impedance are analyzed by the finite element analysis and measured by experiments. Second, a magnetic feedback method in the frequency domain is proposed to obtain the desired magnetization loci. Third, when the specimen is in deep magnetic saturation, the harmonics of magnetic flux density waveform would affect the shape of the corresponding magnetic field strength loci and the accuracy of loss computation. Thus, a waveform compensation method is proposed to eliminate the effects of harmonics. Fourth, the tensor effects of H coils are eliminated by averaging the results of clockwise and counterclockwise rotational experiments. Finally, the 3-D magnetic test system with feedback control, harmonics compensation, and automated data processing is developed. By using the 3-D magnetic tester, samples of nonoriented silicon sheet steel are measured with various excitation models and the results are more reliable than those obtained by experiments without feedback and harmonics compensation.

Comprehensive Magnetic Properties Analysis of the Silicon Steel Considering the Laminated Direction

Comprehensive magnetic properties of the laminated silicon steels are key factors in magnetic core design, which should be measured and modeled by using a new testing method. Comparing with traditional Epstein frame and single sheet tester, a new method of three-dimensional magnetic properties measurement is used for complex magnetic properties of the laminated silicon steels. The comparison of magnetizations between the rolling or transverse direction and the laminated direction are illustrated. Both magnetic hysteresis and core loss features of the silicon steels specimen are measured and analyzed considering the laminated direction. The hysteresis loss, classical eddy current loss, and excess loss are analyzed and compared in different directions. This study can provide dynamic and comprehensive data to design and evaluate performance of electrical machines and power transformers.

Rotational Core Loss of Silicon Steel Laminations Based on Three-Dimensional Magnetic Properties Measurement

Magnetic properties of silicon steel laminations are important features in power transformer and electrical machine design and manufacture. Conventional testing methods such as Epstein Frame and Single Sheet Tester may only consider one direction or one sheet, which may deviate from the real application, particularly in core loss calculation. A 3-D magnetic properties' testing method is proposed in this paper. By using the designed special surface B-H sensing coils, the dynamic magnetic hysteresis properties of a laminated non-grain-oriented silicon steel sample are accurately measured. The relationship between B and H in alternating, 2-D rotational, and 3-D spherical rotational excitations, from 50 to 200 Hz, is studied and analyzed. In order to control the B waveform better, the harmonics of B x and B y signals are analyzed at 50 Hz. The alternating core losses in the rolling, transverse, and laminated directions and the rotational core losses in the xoy plane of this sample at 50, 100, and 200 Hz are calculated and analyzed. Moreover, the core losses in the three directions are well predicted by means of total core loss separation theory.

A Novel Combined $B{-}H$ Sensing Coil in Three-Dimensional Magnetic Properties Testing System

A novel sensing structure with combined B (magnetic flux density) and H (magnetic field strength) sensing coils is used in three-dimensional (3-D) magnetic properties testing system with cubic specimen. In order to accurately calculate and analyze the 3-D magnetic properties from experiment, comprehensive calibration and compensation of the sensing structure must be systematically fulfilled. This paper presents the structure and calibration of the novel surface B-H sensing coils and the accurate expression of B and H calculation by means of coefficient matrix of the sensing coils. Based on the novel sensing coils and accurate coefficients, rotational magnetic properties of a soft magnetic composite material specimen have been measured and analyzed.

Design of a 3-D Rotational Magnetic Properties Measurement Structure for Soft Magnetic Materials

Three-dimensional magnetic properties of the soft magnetic materials should be considered and comprehensively analyzed in electrical engineering, compared with the traditional 1-D and 2-D testing method. A novel 3-D magnetic properties measurement structure with symmetrical “C-type” cores has been designed and modeled. To guarantee the experimental precision and accurately analyze the 3-D magnetic properties of the soft magnetic materials, especially for laminated silicon steel, a symmetrical 3-D magnetic flux path in the magnetization structure fit for given dimension of the cubic specimen has been calculated and modeled. Magnetic flux in each direction has been homogenized and concentrated on the top of the core poles by means of finite element analysis. Therefore, magnetic properties measurement in each direction of the specimen can become practical.

Three-dimensional magnetic properties of soft magnetic composite material at different frequencies

Due to their intrinsic isotropic magnetic properties, soft magnetic composite (SMC) materials are applied in electrical machines in which the magnetic energy can be transported in three dimensions (3-D). However, in real applications, complicated magnetic properties such as anisotropy and nonlinearity, are found, in particular, at ahigh frequency range. This paper studies the 3-D magnetic properties of SMC materials under complicated magnetizations, such as circular, elliptical, and spherical excitations. The magnetic flux density vector B loci, magnetic field strength vector H loci, and core losses at magnetization frequencies ranging from 50–1000 Hz were measured and discussed using an improved 3-D testing system. Experimental results show that rotational core losses are greater than alternating losses at the same magnitude of flux density. In addition, rotational loss increases sharply around the saturation point, but is not observed in alternating loss.

Three-dimensional magnetic properties of soft magnetic composite materials

A three-dimensional (3-D) magnetic property measurement system, which can control the three components of the magnetic flux density B vector and measure the magnetic field strength H vector in a cubic sample of soft magnetic material, has been developed and calibrated. This paper studies the relationship between the B and H loci in 3-D space, and the power losses features of a soft magnetic composite when the B loci are controlled to be circles with increasing magnitudes and ellipses evolving from a straight line to circle in three orthogonal planes. It is found that the B and H loci lie in the same magnetization plane, but the H loci and power losses strongly depend on the orientation, position, and process of magnetization. On the other hand, the H vector evolves into a unique locus, and the power loss approaches a unique value, respectively, when the B vector evolves into the round locus with the same magnitude from either a series of circles or ellipses.

Calibration of Sensing Coils of a Three-Dimensional Magnetic Property Tester

For electrical machines with three-dimensional (3-D) magnetic fluxes, the magnetic properties of magnetic materials under 3-D excitations should be properly determined and applied in machine design and analysis. This paper presents the construction and calibration of the H (field strength) and B (flux density) sensing coils of a 3-D magnetic property testing system, and the correction of measurement error due to the misalignment of sensing coils with excitation fields. The 3-D tester has been used to measure the magnetic properties of soft magnetic composite (SMC), a material specially developed for application of 3-D flux electrical machines. Some 3-D results have been obtained on a cubic SMC sample. The measurement errors caused by the misalignment of sensing coils and excitation fields are corrected by a rotational transformation of coordinates.

Three-dimensional magnetic properties of Bi2CuO4

Magnetic susceptibility and neutron diffraction measurements prove the 3D rather than the 2D or 1D character of magnetic interactions in Bi2CuO4. It has been shown that, at TN=44.6+or-0.3 K, Bi2CuO4 undergoes a transition to an antiferromagnetic state. The magnetic unit cell coincides with the chemical cell (k=0) and is of type I. The value of magnetic moment is either (0.53+or-0.1) mu B or (0.75+or-0.1) mu B depending on whether the magnetic moments are oriented parallel or perpendicular, respectively, to the c axis. The effective magnetic moment of the Cu2+ ion is (1.80+or-0.2) mu B. The results of theoretical susceptibility calculations for the BCT lattice model and for the SQ lattice model together with the molecular-field interactions have been presented and compared with the experiment.