Core Loss Estimation Research Articles

Core Loss Estimation of Various Materials Magnetized With the Symmetrical/Asymmetrical Rectangular Voltage

Core losses were estimated for various magnetic core materials magnetized with a duty-cycle-changed symmetrical and asymmetrical rectangular voltage. Each voltage waveform is applied to a transformer and a dc reactor in a dc/dc converter, respectively. Core losses were measured for the four typical magnetic core materials often used in power electronics: 3% grain-oriented silicon steel sheet, 6.5% silicon steel sheet, amorphous material, and nanocrystalline material. Measurement results were evaluated by the loss separation model. An approximation method was proposed for the core loss magnetized with asymmetrical rectangular voltage that divides the total core loss into the core loss of the magnetization from <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-B_{m}$</tex> </formula> to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$B_{m}$</tex></formula> and that of the magnetization from <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$B_{m}$</tex></formula> to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-B_{m}$</tex> </formula> . This method was confirmed to approximate the core loss accurately except for silicon steel sheet in an extreme duty cycle condition. However, it was demonstrated experimentally that dc component of the magnetic field strength caused this error.

The Minor Hysteresis Loop Under Rotating Magnetic Fields in Machine Laminations

In rotating ac machines, the saturated flux density waveforms contain harmonics, which create minor hysteresis loops. The minor hysteresis loops in machine laminations constitute an additional loss which requires modifications in traditional core loss formulas. This causes a serious challenge in core loss estimation. The task becomes more competitive under rotating magnetic fields, where the minor loop behavior has not been investigated yet. This paper highlights the problem of harmonics in rotating fields and its effect on the core loss estimation. In addition, the behavior of minor loops under rotating fields is compared with the minor loops under pulsating fields. Measurements were carried out on a nonoriented silicon steel sample of M36G29 with different fundamental frequencies of interest to the industry, 60 Hz and 400 Hz, with consideration of the third harmonic at each frequency. A design of magnetizing test fixture based on an electromagnetic Halbach array is used to perform these measurements. Results are presented and discussed.

Magnetic Circuit Model Considering Magnetic Hysteresis

SUMMARY Quantitative estimation of core loss considering magnetic hysteresis property is strongly required to develop high-efficient electrical machines. This paper presents a novel magnetic circuit model considering magnetic hysteresis. In the proposed model, dc hysteresis loss is calculated by the Landau–Lifshitz–Gilbert (LLG) equation, while classical and anomalous eddy current losses are calculated in the magnetic circuit. It is demonstrated that the hysteresis loop under PWM wave excitation can be expressed by the proposed model. The validity and effectiveness of the method are proved by comparing with measured values.

Core Loss Prediction in Electrical Machine Laminations Considering Skin Effect and Minor Hysteresis Loops

This paper presents a method for the estimation of core losses in electrical machine laminations exposed to high-frequency and nonsinusoidal excitations by using only low-frequency measurements. The developed model takes into account the nonuniform distribution of the magnetic field inside the lamination. Accurate core loss prediction in the presence of minor loops is achieved using the energetic model to calculate the quasi-static hysteresis loops. The results are verified experimentally by comparing to the measured core losses in laminations exposed to the flux waveforms in different sections of an inset permanent magnet machine. The comparison between measured and calculated core losses shows excellent agreement, confirming the validity of the model.

Estimation of Core Losses on Electrical Steel Laminations in Wind Generators Using Epstein Frame and Expanded GSE Method

The paper intends to study the core losses of non-oriented electrical steel laminations under high frequency voltage excitations. The measurement of core losses of the electrical steel laminations in Epstein Frame is implemented step by step from 50 Hz to 5000Hz. The accuracy of results evaluated from Expanded GSE method is compared with those tested by Epstein Frame. The core loss database for three different kinds of medium, medium-high and high quality electrical steel laminations (50CS350, 50CS470, 50CS600) is completed in the paper. Also, 85 test points of core loss data are established in the flux density ranging from 0.3T to 1.8T and in the power supply frequency ranging from 50Hz to 5000Hz. Maximum core loss value is close to 443W/kg. The tested core loss data and the Expanded GSE models are useful and may cover for the applications of large-scale wind-driven generators and general motors. They also enough provide designers with the accurate information to minimize the core losses of wind turbine generators.

Investigation of GIC effects on core losses in single phase power transformers

Investigation of GIC effects on core losses in single phase power transformers This paper presents a method for estimation of core losses in banks of single phase power transformers that are subjected to an injected DC current such as geomagnetically induced currents (GIC). The main procedure of the core loss calculation is to obtain a magnetic flux density waveform in both time and location by using a novel algorithm based on 3D FEM inside the core and then to calculate the loss distribution based on loss separation theory. Also, a simple and effective method is proposed for estimation of losses of asymmetric minor loops by using combination of symmetric loops. The effect of DC biasing on core losses in single phase power transformers is investigated and the sensitivity of core type and material is evaluated. the results shows that DC current biasing could increase core losses up to 40 percent or even more.

Power Transformer No-Load Loss Prediction with FEM Modeling and Building Factor Optimization

Estimation of power transformer no-load loss is a critical issue in the design of distribution transformers. Any deviation in estimation of the core losses during the design stage can lead to a financial penalty for the transformer manufacturer. In this paper an effective and novel method is proposed to determine all components of the iron core losses applying a combination of the empirical and numerical techniques. In this method at the first stage all computable components of the core losses are calculated, using Finite Element Method (FEM) modeling and analysis of the transformer iron core. This method takes into account magnetic sheets anisotropy, joint losses and stacking holes. Next, a Quadratic Programming (QP) optimization technique is employed to estimate the incomputable components of the core losses. This method provides a chance for improvement of the core loss estimation over the time when more measured data become available. The optimization process handles the singular deviations caused by different manufacturing machineries and labor during the transformer manufacturing and overhaul process. Therefore, application of this method enables different companies to obtain different results for the same designs and materials employed, using their historical data. Effectiveness of this method is verified by inspection of 54 full size distribution transformer measurement data.

Core loss estimation in three‐phase transformer using vector hysteresis model and classical loss model incorporated in 2D magnetodynamics

AbstractThis paper deals with the computation of the magnetic field and core loss in a three‐phase three‐limb transformer at no‐load. The computational algorithm consists of the vector hysteresis model incorporated in 2D magneto‐dynamics via the differential reluctivity tensor. The hysteretic nonlinearity is handled by a simple iteration scheme. The eddy‐current losses in the laminated steel core are accounted for by considering an additional conductivity matrix in the FE equations. The magnetisation‐dependant vector Preisach model with an analytical expression for the distribution function is adopted for describing the hysteretic constitutive law in the rolling and transverse directions of the laminations. The parameters and mean field term are fitted on the basis of a set of BH‐symmetric (quasistatic) loops. Numerical results are presented that confirm the effectiveness of the proposed method for the no‐load simulation of the transformer in the transient and the steady‐states.

Estimation of MnZn ferrite core losses in magnetic components at high frequency

This paper deals with a magnetic modeling for the estimation of the dynamic losses in soft ferrite cores. A time-domain MSPM based algorithm for the hysteresis losses evaluation, added to a simplified, one-dimensional modeling of the eddy current losses, are used to predict the total specific losses in cores subjected to a.c. and distorted wave-forms. Experimental analysis show satisfactory capability of prediction of the modeling proposed, used as a CAD tool.

Estimation of core losses under sinusoidal or nonsinusoidal induction by analysis of magnetization rate

This work deals with a method of analysis that estimates the increase of core losses under sinusoidal and nonsinusoidal inductions. The estimation can be carried out by correlating instantaneous magnetization power (PM) or the instantaneous magnetic field (H) as a function of the magnetization rate (dB/dt) and the induction level (B). Experimentally, this correlation can be obtained under triangular waveform induction tests. Predictions under sinusoidal and nonsinusoidal inductions were made in oriented and nonoriented FeSi steel sheets. The predictions, when compared to experimental results, show an error of up to 3% for nonoriented materials and of up to 5% for oriented materials. Also, this method allows the prediction of the loss loop shapes. The limitations and perspectives of the method are considered in this work.

Estimation of Core Losses under Sinusoidal or Nonsinusoidal Induction by Analysis of Magnetization Rate

This work deals with a method of analysis that estimates the increase of core losses under sinusoidal and nonsinusoidal inductions. The estimation can be carried out by correlating instantaneous magnetization power (PM) or the instantaneous magnetic field (H) as a function of the magnetization rate (dB/dt) and the induction level (B). Experimentally, this correlation can be obtained under triangular waveform induction tests. Predictions under sinusoidal and nonsinusoidal inductions were made in oriented and nonoriented FeSi steel sheets. The predictions, when compared to experimental results, show an error of up to 3% for nonoriented materials and of up to 5% for oriented materials. Also, this method allows the prediction of the loss loop shapes. The limitations and perspectives of the method are considered in this work.

Core losses estimation in a multiple teeth per stator pole switched reluctance motor

This paper presents a suitable approach to loss prediction in a multiple-teeth-per-stator-pole switched reluctance motor based upon the conventional core losses equation and taking into account the complicated flux variations in the magnetic circuit. Flux waveform in a part of the stator yoke is measured and used to predict the flux waveforms of the other parts of the magnetic circuit of the motor. These flux waveforms are then used to predict the core losses in the motor. Comparison between the predicted and measured values shows a 25.8% discrepancy. >

Estimation of core losses when the flux waveform contains the fundamental plus a single odd harmonic component

This paper examines the behaviour of the core losses in thin laminations when the flux density waveform is highly distorted at peak flux densities of up to 2.0 T. It is shown that the presence of harmonics can increase the loss significantly over the value that exists when the flux density waveform is purely sinusoidal. A simple method that corrects the eddy current component of core loss for the effects of flux harmonics is used to estimate the total loss due to a distorted waveform. Provided the waveform does not contain harmonics greater than the 5th, it is shown that such a method of estimation yields acceptable results for the distortion levels encountered in practice.