Epstein Square Research Articles

Measurement equipment and result analysis of B-H curve of current transformer core material under mixing frequency.

To examine the effect of mixed-frequency excitation conditions on the hysteresis and loss characteristics of ferromagnetic materials, this paper shows how to construct magnetic property test equipment for electrical steel using Epstein's square circle. Experiments were carried out to assess the hysteresis and loss properties of oriented silicon steel wafers under mixed-frequency sinusoidal operating conditions with different occupancy ratios. It used heterodyne extraction to investigate the effect of different occupancy ratios of industry and magnetization frequency on the hysteresis and loss characteristics of oriented silicon steel sheets.

Experimental and Engineering Simulation of Loss Characteristics of Silicon Steel Wafers Based on Levenberg-Marquardt Optimization Algorithm

Abstract The loss characteristics of 20WTG1500 silicon steel wafers are simulated and studied by using the Epstein square circle method. First, the loss-measured data are fitted based on the classical Bertotti loss model. When working, a Levenberg-Marquardt (L-M) algorithm is proposed to calculate the parameters of the loss model accurately. For the problem of significant calculation errors of hysteresis loss and stray loss in the classical loss separation model, a variable parameter closely related to the magnetic induction intensity is constructed by using the fixed parameter values of the classical loss model. Then, the loss improvement model is proposed. The accuracy of the improved model is proved by comparing the fitting results of the enhanced model with the measured data.

Analysis of the Magnetic Properties of Ultra-Thin Grain-Oriented Silicon Steel and Fe-Based Amorphous Alloys from Power Frequency to Intermediate Frequency

The magnetic properties of a 0.10 mm ultra-thin, grain-oriented (UTGO) silicon steel and an Fe-based amorphous (FBA) alloy under sinusoidal excitation were experimentally researched, and the magnetic field strength and iron loss of the two materials under different frequencies and magnetic densities were obtained. Based on the measured data, the magnetization and loss characteristics of the two materials were analyzed and compared. Furthermore, two Epstein square ring models of the same dimensions and different materials were designed, and the reliability of the models was verified. Then, the electromagnetic characteristics of the two Epstein square ring models at higher and lower frequencies were calculated using the finite element method, and the iron losses were obtained and compared. The results show that the FBA alloy has good application characteristics at low frequencies and low power, and the 0.10 mm UTGO silicon steel has good application characteristics at high frequencies and high power. This research provides important data, promoting the application of these two materials in new energy equipment.

Study on the influence of ultra-thin non-oriented silicon steel sheet on the performance of ultra-high-speed permanent magnet motor

The ultra-high-speed permanent magnet motor has the characteristics of high-power density, small size, and high speed, but there are problems with it, such as generation of local excessive heat and obvious vibration and noise. In order to reduce the loss and improve the efficiency of the motor, in this study, ultra-thin silicon steel sheets are used as the material of the iron core of the motor, and two non-oriented silicon steel sheets with different thicknesses—0.05 and 0.15 mm—were selected. First, we use the Epstein square ring electrical steel sheet magnetic properties test to determine the magnetic properties and the loss properties of the two ultra-thin non-oriented silicon steel sheets under working conditions. Then, we use electromagnetic simulation software to calculate the magnetic performance and the temperature rise performance of two kinds of motors with different materials. Finally, through the test of the prototype, we know the difference in the influence of the two kinds of silicon steel sheets on the performance of air compressors. We hope the outcome of the study will provide technical support for optimizing the design of ultra-high-speed permanent magnet motors for air compressors.

The nonlinear characteristics of transformer broadband

At present, the modeling of the transformer broadband nonlinear characters is based on the nonlinear features of 50Hz, so there are still some questions. In this paper, the magnetic hysteresis loop of the silicon steel in the the range of 50Hz to 100kHz is measured by using a measuring system composed of a 25cm Epstein square coil and an amh-1m magnetometer. The J-A parameters of the silicon steel core in the frequency wide range of the range of the optimized by using the hybrid means on the oneran fish swarm and L-M. Then, the nonlinear core model of transformer based on J-A parameters is set in PSPICE. Based on the model, the transformer simulation circuit is built. By applying sinusoidal voltage signal of the specific frequency to the nonlinear transformer model with the specific frequency, the non-linear characters of the transformer in wide frequency range areed. It is found the nonlinear characters of the transformer core change dramatically with the change of the frequency. Therefore, in the broadband nonlinear modeling of the transformer, using the nonlinear characters at 50Hz to nonlinear the broadband model will lead to large error. In the follow-up modeling research, scholars should consider the nonlinear characters of the transformer to the set the model, and try to use the nonlinear characters of the transformer under the frequencies for the broadbandlinear modeling.

Study on Magnetic Properties of Magnetic Materials with Multiple Factors

With the vigorous development of the power industry, the demand for electromagnetic equipment is also increasing. It is of great significance to accurately simulate the magnetic properties of the magnetic materials under the external conditions of different frequencies and pressures in the electrical equipment for the precise design and improvement of the performance of the equipment. First of all, this paper briefly introduces the research background of electrical magnetic materials. Since this paper is based on the practical application of engineering, the Epstein square method and the ring sample method are used to record and test the magnetic properties of the silicon steel sheet under the influence of frequency and pressure. Finally, based on the processed and analyzed experimental data, this paper summarizes the magnetic properties of magnetic materials, which theoretically analyzes and explains the possible reasons to serve for engineering application.

Comparison between measured and computed magnetic flux density distribution of simulated transformer core joints assembled from grain-oriented and non-oriented electrical steel

The flux distribution in an overlapped linear joint constructed in the central region of an Epstein Square was studied experimentally and results compared with those obtained using a computational magnetic field solver. High permeability grain-oriented (GO) and low permeability non-oriented (NO) electrical steels were compared at a nominal core flux density of 1.60 T at 50 Hz. It was found that the experimental results only agreed well at flux densities at which the reluctance of different paths of the flux are similar. Also it was revealed that the flux becomes more uniform when the working point of the electrical steel is close to the knee point of the B-H curve of the steel.

Identification of the Jiles-Atherton Model Parameters Using Simulated Annealing Method

This paper presents a method and the experimental measurement system for the determination of Jiles-Atherton model parameters of the 30ZH120 electrical steel sheet. The paper utilizes Epstein Square devices to proceed with the experiment and measurement on a group of hysteresis loops of some certain transformers which use the 30ZH120 electrical steel sheet under two different lap ways. The approach relies on the simulated annealing optimization method in order to minimize the error between the measured and modeled hysteresis curves and yield the best five Jiles-Atherton model parameters. A convenient program, based on the Simulink platform, that can identify the J-A model parameters automatically from the experimental saturated hysteresis loop which is used to model the nonlinear characteristics of the electrical steel sheet, is developed. Research shows that the simulated annealing optimization method gets satisfactory results.

Measurement Research on Magnetic Properties of Electrical Steel Sheet under DC Bias Conditions

In order to acquire the magnetic properties parameter of transformer core under DC bias conditions, also to reveal the accurate analysis and judgment on the operating characteristics of transformer under the DC bias, this thesis utilized two Epstein Square devices to proceed the experiment and measurement on magnetization curve of some certain transformer which used the 30ZH120 electrical steel sheet under four different lap ways. This paper provided the measure method of bias magnetic density under laboratory conditions, meanwhile it offered the bias magnetization curve and the loss curve. The measure consequence comparison between the electrical sheet steel and the transformer model showed that direct oblique way lap can be more realistically reflected the magnetization characteristic of transformer which worked in the DC bias conditions. For Large Transformer which was difficult to measure the magnetic properties provided a convenient measurement methods, and offered the experiment facts to the theory study of the DC bias transformers.

A computerised Rogowski-Chattock Potentiometer (RCP) compensated on-line power-loss measuring system for use on grain-oriented electrical steel production lines

A computerised on-line power-loss testing system has been developed, based on the RCP compensation method for use on grain-oriented electrical steel production lines. The system power-loss results have been correlated with Epstein square tests and agreement to within ±4.9% has been achieved.

Correlation between normal flux transfer from lamination to lamination during the magnetization process with static domain structures in grain oriented 3% silicon iron

Grain oriented 3% silicon iron is widely used as magnetic core material in power devices. It is usually assessed on the basis of its magnetic losses when magnetized as single strips or in the Epstein square. When material is built into cores and magnetized, some flux passes normal to the plane of the laminations and increases the losses of transformers and rotating machines. Pairs of strips were placed together and magnetized at 50 and 60 Hz at ac longitudinal flux densities from 1.0 to 1.8 T and the normal flux density, BN transferred between them was calculated from the emfs induced in search coils located between the strips. Static domain structures were observed using a colloidal technique. Values of BN have been correlated with the domain structures, grain size, and boundary effects. BN was found to be dependent on the static wall spacing in adjacent grains and varied between 0.5 and 3.0 mT with a repeatability better than ±5%. Most large grains had low surface magnetic charge at their boundaries and BN was low. The opposite was found where the flux was transferred between small, not so well oriented, grains. This large normal flux transfer between poorly oriented small grains causes small additional losses in laminated cores.

Determination of AC magnetic power loss of electrical steel sheet: Present status and trends

A brief survey of the status of work in the higher induction and frequency ranges is given and recent papers on the measurement of rotational losses are reviewed. The determination of the magnetic losses in alternating fields is considered, in partucular regarding the performance of those magnetic circuits most widely used in loss measurements. New and revised data contribute to the elucidation of the systematic errors of the Epstein square. The Epstein samples and plate samples, both of various materials, were used for measurements with single sheet testers, whereby the field strength was determined both from the magnetizing current by means of a precision resistor and direct, using field sensing coils. From these results conclusions for the appropriate value of the effective magnetic path length can be drawn. The electric power measurement particularly as regards digital procedures, calibration and uncertainties is briefly discussed.

Factors affecting localised flux and iron loss distribution in laminated cores

The paper reviews the increasing importance of iron losses in magnetic cores of transformers and rotating machines and shows how it can be better understood with an increased knowledge of flux distribution in the devices. The importance of an understanding of flux distribution in Epstein square testing is emphasized and some problems in Epstein measurement are discussed. The use of high permeability silicon-iron in transformer cores can cause a reduction of the building factor in some designs and it is shown how the flux distribution in such cores can be adversely affected and increase the building factor when high quality steel is used.

Building factor of a 100 KVA 3 phase distribution transformer core

The no load iron loss in laminated transformer cores is always greater than the nominal loss of the electrical steel laminations, as measured in an Epstein square or a single strip tester, by a factor known as the building factor. It is as important to improve the building factor of the transformer cores as it is to attempt to improve the basic properties of the steel since it is meaningless to build a transformer with a poor building factor using good quality steel. In this paper an attempt has been made to break down the measured loss of a 100 KVA 3 phase distribution transformer into several components to obtain a good indication of the most important parameters which affect the building factor. Forty two percent of the loss was found to occur in the limbs and yokes, whereas, the loss in the T-section areas accounted for only five percent. The losses due to the third harmonic circulating flux, the mean stress level and the stacking method were estimated to be 10%, 17% and 18% respectively. The unaccounted loss of eight percent could be partly attributed to the higher harmonics and possibly some errors in estimation.

Causes of some errors in measurements in grain-oriented silicon-iron using the epstein square

Measurements were made on grain-oriented silicon-iron in an Epstein square to show the importance of using the appropriate stacking method when the samples are not cut parallel to the rolling direction. The reason why one stacking method should be used is discussed.

Harmonic losses in a three phase transformer core

The iron loss of laminated cores is always greater than the nominal loss of the steel as measured in an Epstein Square or single strip tester. The extra loss is due to a number of factors. Flux harmonics have been measured locally in individual laminations of grain-oriented silicon-iron in a 3 phase transformer core and the loss associated with the harmonic components has been estimated. For the experimental core used, the loss associated with the harmonics in the yokes and limbs was 15% of the total loss, and corner loss accounted for 17% of the total. The calculated loss in the core accounted for over 80% of the measured loss, the difference being due to the effect of mechanical stress and also the errors in estimating the losses.

Effects of stacking methods on Epstein-square power loss measurements

The Epstein square is the standard loss-measuring apparatus for electrical steel laminations tested at power frequencies. Investigations have shown that, if laminations of grain-oriented 3.25% silicon-iron are cut at various angles to the rolling direction, the apparent powerloss depends on the type of stacking used. Two types of stacking were found to give loss values close to single-strip measurements, whereas another type, and a random stacking method, gave apparent losses as much as 50% less than single-strip values. The effect is greater with betteroriented material. The main cause of the difference in apparent losses stems from the flux transfer mechanism at the corners which cause the corner loss in some cases to be less than the limbloss, thus giving artificially low apparent losses.

Some aspects of effects of longitudinal and normal stress on power loss and flux distribution within a transformer core

An experimental 1.0 m Epstein square has been constructed in which all the limbs could be flattened to 1.5×105 N/m2 and two opposite limbs could be stressed longitudinally to ±13.8×106 N/m2 Power-loss measurements were made on cores of 46-grade and 56-grade grain-oriented silicon-iron subjected to combinations of longitudinal and normal stress. The power loss (at 1.5 T) increased by only about 10% owing to the normal compression, but linear stress increased the loss by up to 40% (at 9.65×106 N/m2 compression). When the applied linear stress was greater than about 5.8 × 106 N/m2, the normal stress restricted the power-loss increase. The effect of normal stress on a 45° mitred-overlap and a double-overlap joint were investigated. In the double-overlap joint, the flux did not deviate from the rolling direction of the laminations. Airgaps in the mitred-overlap joint and the length of the overlap were both found to have a pronounced effect on the corner loss. The lower-loss-grade material was found to have a lower stress sensitivity of power loss to both normal and longitudinal stress.

Measurement of the total loss of cold-rolled nonoriented 3% silicon iron using an Epstein square

Cold-rolled nonoriented magnetic sheet steel has better magnetic properties when magnetised along the rolling direction than when magnetised across it. For example, losses along the rolling direction are 15–20% below the mean. Owing to this difference in properties, values of core loss obtained when testing in an Epstein square may differ by as much as 4.5% according to the arrangement in the limbs of pieces cut along and pieces cut across the rolling direction. These differences have been investigated, and some of them have been explained on the basis of nonuniform flux and flux-waveform distortion. The best arrangement of the sample for testing is shown to correspond with that recommended in BS 601: Part 1: 1959.