Core Loss Calculation Research Articles

Diagnosis and performance analysis of three-phase permanent magnet synchronous motors with static, dynamic and mixed eccentricity

Albeit permanent magnet synchronous motors (PMSMs) under static and dynamic eccentricity have been studied in few papers, so far mixed eccentricity has not been investigated. In this study, a novel index is introduced for dynamic and mixed eccentricity fault diagnosis in PMSM. This index is the amplitude of side-band components with a particular frequency pattern that is extracted from spectrum analysis of the motor torque. The index provides precise detection of the eccentricity occurrence, recognition of its type and determination of its degree. To evaluate the ability of the proposed index for the eccentricity diagnosis and estimation of its severity, first the correlation between indices, static and dynamic eccentricity degrees are calculated. The type of eccentricity is determined using k-nearest neighbour (KNN) classifier. At the next step, a three-layer artificial neural network is employed to estimate the eccentricity degree of torque profiles based on their type of eccentricity. After all, a white Gaussian noise is added to the simulated torque and robustness of the proposed index is analysed with respect to the noise variance. Meanwhile, the spectrum analysis of the stator current in faulty PMSM under static, dynamic and mixed eccentricities is studied and the influence of these eccentricities on ohmic, hysteresis and eddy current losses of PMSM are presented. In this examination, the time-domain elemental flux density waveforms and various time-domain waveforms of motor winding currents are computed using time stepping finite element method (TSFEM) for core loss and ohmic loss calculations punctually. The accuracy of obtained simulation results is verified using experimental results.

Dynamic Characteristic Analysis Considering Core Losses in Transverse Flux Linear Machine With Solid Cores

This paper deals with a method for dynamic characteristic analysis considering core losses in transverse flux linear machines (TFLMs) with solid cores. This paper focuses on how to calculate the core losses of solid cores and how to apply the core losses to the dynamic simulation. The magnetic field characteristics, which are used for the core loss calculation and dynamic simulation, are calculated by using a 3-D equivalent magnetic circuit network analysis method. The accuracy of the proposed core loss calculation and dynamic simulation methods are examined by comparing the input currents of the dynamic simulation model with the measured input current of two TFLM prototypes.

Loss Characterization and Calculation of Nanocrystalline Cores for High-Frequency Magnetics Applications

The loss density of the nanocrystalline magnetic material is experimentally characterized up to 500 kHz and above 1 Tesla in this paper. B-H hysteresis magnetization curves and loss density of the material under various operating temperatures up to 150degC are measured and presented. The core preparing effect on magnetic loss density is also identified by experiments, which provides information necessary to practical magnetic designs. A new empirical core loss calculation method, flux-wave-form-coefficient Steinmetz equation, is proposed and verified for the nanocrystalline material under resonant operations, which are often employed in high-frequency power converter applications. The proposed approach is either more accurate or easier to use than the previous methods.

An Improved FE-Based Phase Variable Model of PM Synchronous Machines Including Dynamic Core Losses

An improved finite-element (FE)-based phase variable model of PM synchronous machines is developed to provide an accurate machine model for drive and control applications. The improvements add the effects of core losses to the phase variable model as well as its variation with the rotor position, which are obtained from steady-state FE solutions of the machine covering a complete ac cycle. Details on the creation of the improved model, its implementation, dynamic core loss calculation using FE computation, in addition to applications are presented in the paper. The originality of this work is based on the fact that a fast and more comprehensive PM machine model has been proposed for machine control studies

A Practical, Accurate and Very General Core Loss Model for Nonsinusoidal Waveforms

Nonsinusoidal voltage waveforms are quite common in high frequency power conversion magnetics. Low frequency nonsinusoidal waveforms are also common in ac motor applications with waveforms such as pulsewidth modulation and six-step. Previous attempts to model these losses, based on the Steinmetz equation, can work only in a limited range of frequencies, flux density excitations, and waveforms. In this paper, we present a very practical, yet very general and accurate model, for core loss calculations in case of nonsinusoidal voltage waveforms. We show the model is equally applicable to low and high frequencies, metallic as well as nonmetallic (e.g., ferrites) core materials, by comparing the model prediction with measured data for various waveforms, frequencies, and flux densities. The model can be used for the design of high frequency transformers and inductors for use in switched mode power supplies. The model can also be used for ac motors where it is hard to estimate derating factor and to avoid uncontrolled temperature rise

Core loss evaluation of segment core in turbine generators by torque method

AbstractThis paper presents core loss evaluation of a turbine generator model stator. The stator configuration does not make the magnetic flux distribution uniform, and the induction harmonics make the core loss calculation difficult. In this evaluation, the core losses are measured by rotating stator torque.As a result of the measurements, a half‐lap‐stacked stator obtains lower core losses and larger percentage of eddy current losses than a block‐stacked stator. In addition, a gap between each segment makes in‐plane eddy current loss increase. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 64–71, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20407

Study of Parameters of a Tripler Using the Finite Element Method of Harmonic Balance

In this paper, a new harmonic balance analysis approach based on the finite element method (HBFEM) is used to calculate the equivalent leakage reactance and the core loss in a magnetic frequency tripler. The HBFEM presented can be used to analyze harmonic magnetic field for time periodic magnetic field with B/spl sim/H curve described by any high order polynomial. Consequently, the current and flux density waveforms include many harmonic terms caused by saturation. An equivalent leakage reactance model of magnetic frequency tripler is presented based on the harmonic terms. The resulted harmonic-rich flux density waveforms are used to calculate core losses and equivalent leakage reactance. Simulation results are compared with experiment results and it is shown that the approach and model are correct and practical.

トルク法によるタービン発電機セグメントコアの鉄損評価

This paper presents core loss evaluation of a turbine generator model stator. The stator configuration does not make the magnetic flux distribution uniform, and the induction harmonics make the core loss calculation difficult. In this evaluation, the core losses are measured by rotating stator torque. As a result of the measurements, a half-lap-stacked stator obtains lower core losses and larger percentage of eddy current losses than a block-stacked stator. In addition, a gap between each segment makes in-plane eddy current loss increase. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 64–71, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20407

A Dynamic Core Loss Model for Soft Ferromagnetic and Power Ferrite Materials in Transient Finite Element Analysis

A dynamic core loss model is proposed to estimate core loss in both soft ferromagnetic and power ferrite materials with arbitrary flux waveforms. The required parameters are the standard core loss coefficients that are either directly provided by manufacturers or extracted from the loss curve associated with sinusoidal excitation. The model is applied to calculating core loss in both two-dimensional and three-dimensional transient finite element analysis, and the results are compared with measured data.

Core losses in claw pole permanent magnet machines with soft magnetic composite stators

This paper presents the core loss calculation in soft magnetic composite (SMC) samples and a claw pole permanent magnet machine with SMC stator. By using finite-element analysis of the magnetic field, the total core loss is computed by separating the hysteresis (alternating and rotational, both purely circular and elliptical), eddy current, and anomalous losses in each element when the rotor rotates. The coefficients for each loss component are determined by a loss separation procedure and the experimental data obtained by a single sheet two-dimensional core loss testing system.

Energy loss spectroscopy of dislocations in GaN and diamond: a comparison of experiment and calculations

We present results of electron energy loss spectroscopy (EELS), carried out with nanometer spatial resolution in a dedicated scanning transmission electron microscope (STEM), of thin films of GaN and diamond. We are able to extract the scattering intensity down to energy losses of 2 eV with an energy resolution of 0.36 eV. This is achieved by using a high spectrometer dispersion. We specifically attempt to determine changes in the electronic bandstructure, reflected in the inelastic low loss scattering distribution at dislocations. Ab initio calculations within the local density approximation to density functional theory of the bandstructure used to simulate low electron energy loss spectra reveal bandgap states associated with all dislocation types in GaN as well as in diamond [Phys Rev B65 (2002) 245–304; Phys Rev B 65 (2002) 205–206]. Core loss calculations of GaN predict potential shifts at edge dislocations due to the piezoelectric effect. The theoretical findings were in very good agreement with the measurements.

Accurate prediction of high-frequency power-transformer losses and temperature rise

The high-frequency power-transformer design equations for winding and core losses and temperature rise were reviewed from literature and formulated for spreadsheet calculations using material (Steinmetz loss coefficients, ferrite resistivity, copper resistivity), geometry (core area, core length, winding area, winding length), winding (number of primary turns, copper fill factor, primary to secondary area ratio) and excitation (input voltage, switching frequency, duty cycle, current harmonic components) parameters. The accuracy of each design issue was first validated and quantified separately using regression analysis. Calculated core losses, winding AC-resistance equations and heat transfer capacity calculations were compared with the results from calibrated heat sink measurements, finite-element method (FEM) analysis and measurements using thermal test blocks, respectively. Finally three EFD20 type transformers (solid wire, noninterleaved foil and interleaved foil winding) were fitted into an active clamp forward converter (100-300 kHz switching frequency, 0-78 W throughput power) for comparison between the theory and experiments. Standard error of predicted core losses and heat transfer capacity were determined to be 0.0581 and 0.15 W, respectively. The results of the in circuit tests suggests that the transformer total losses can be predicted with the average standard error below 0.2 W with datasheet type information only. The most significant uncertainty was heat conduction through and losses generated in the interconnecting wires between the test transformer and other converter components.

A model of non-homogeneous damped electromagnetic wave and heat equation in ferrite materials

This study uses a closely coupled model to treat the core loss of ferrite by the combination of non-homogeneous damped electromagnetic wave and heat equation. The heat dissipation of ferrites is caused by the core loss, which is a summation of magnetic, dielectric and eddy current losses. Explicit finite difference method solves the coupled equations to calculate core loss and compares it with the measured results. Those results show that this method can be used to analyze electromagnetic and thermal field with temperature dependence of ferrites.

Flux distribution and core loss calculation for single phase and five limb three phase transformer core designs

This paper presents results of an analytical core loss calculation method developed for single phase and five limb three phase core types. Shown are calculation results of flux distributions, flux density waveshapes, spatial flux density curves and loss distributions in cores other than the 3 phase-3 limb core. The analytical results show that the flux distribution is essentially uniform in the single-phase 2 limb and 3 limb cores. The flux waveforms are also shown to be essentially sinusoidal in different regions of the core. However, for the single-phase 4 limb core and the three-phase 5 limb core, the flux distribution is nonuniform and flux waves are very distorted. The calculated values of core losses were, generally, in excellent agreement with tested core losses of actual commercial transformers. The results on the very large 4 and 5 limb cores show that the production complexity of these cores cause a slightly higher tested core loss which needs to be included in the development of the core loss calculation for these cores.

Magnetic flux distributions in transformer core joints

This paper presents results of a rigorous analytical study performed in order to understand the role which joints play in determining the performance of cores of power and distribution transformers. The paper presents the details of the magnetic flux distribution and redistribution in the core joint region along the core stack height direction as a function of the operating flux density, core joint material, joint configuration, and joint design parameters. The results are presented for both conventional and step-lap joints. The results illustrate the benefits of the step-lap joint in reducing core losses, noise and excitation current. The results also explain the impact of overlap length, the number of laminations per step, and the contribution of the joint region to the whole core performance. The calculated flux density wave shapes in the joint region were found to be in good agreement with measured wave shapes. The results presented in this paper have been used in developing an accurate calculation of core losses for both power and distribution transformers. They have also been used to arrive at the optimum core joint configuration for a transformer core.

An improved iron loss estimation for permanent magnet brushless machines

This paper presents an improved approach for predicting iron losses in permanent magnet brushless machines. The new approach is based on the fundamental concept that eddy current losses are proportional to the square of the time rate of change of flux density. Expressions are derived for predicting hysteresis and eddy current losses in the stator teeth and yoke. The so-called anomalous or excess losses, caused by the induced eddy current concentration around moving magnetic domain walls and neglected in the conventional core loss calculation, are also included in the proposed approach. In addition, the model is also capable of accounting for the stator skewing, if present. The core losses obtained from the proposed approach are compared with those measured on an existing PM motor at several operating speeds, showing very good agreement.

Modeling of iron-loss components of grain-oriented silicon steel for accurate calculation of core losses of power and distribution transformers

Accurate estimation of iron-loss components of grain oriented silicon steel plays an important role in accurately predicting the core loss performance of power and distribution transformers. Existing practice among design engineers is to approximate the material iron loss performance by a simple curve-fit, like a polynomial, This paper presents the development of an improved analytical model which consists of terms that explicitly represent loss components contributing to the total iron loss of the transformer core material. These are expressed in terms of the operating flux density, frequency, and lamination thickness. Not only is the developed model simple and practical, but it also provides transformer design engineers with accurate understanding of the behavior of each loss component. The results presented here demonstrate the excellent accuracy resulted from using the model in calculating the transformer core loss performance at the design stage.

Calculation of spatial loss distribution in stacked power and distribution transformer cores

This paper describes an analytical solution to use a generic 2D finite difference method to accurately calculate the quasi 3D spatial distribution, components, and total core losses in transformer cores. The solution takes into account: (1) magnetic anisotropy and nonlinearity of the core material; (2) all components of iron losses of the core material, including losses in directions other than the rolling direction; and (3) joint model and localized losses due to the distorted flux distribution in the joint regions (due to core gaps) across the core-stack. The results are used to: (1) calculate very accurately the total core losses of a transformer at the design stage every time, for all core materials, at all operating inductions, for all core geometries, for both 50 Hz and 60 Hz; (2) understand the contribution of cross losses, harmonics, and joints to the total losses of a core; (3) evaluate the impact of various joint attributes, such as, type of joint, number of steps, number of laminations per step, size of gaps, and lamination thickness on the total performance of the core; and (4) improve the core loss performance of transformers by optimizing core design and core material parameters. This paper presents the analysis as applied to 3-phase, 3-limb cores. The paper also presents the results of the extensive experimental/test verification performed on a number of model cores in the lab as well as on a large number of actual commercial transformer cores with excellent agreements. The results have been used to calculate core losses of stacked power and distribution transformers with consistent accuracy.

Core losses and efficiency of electrical motors using new magnetic materials

Core losses of an 18.5 kW asynchronous motor were measured and computed, by means of a suitable electromagnetic fields package, improved for core loss calculation. The results show that a 1 to 3% improvement in efficiency is possible by replacing the conventional soft laminations by new materials. The differences between measurement and computation are mainly attributed to rotating fields inside the stator.

A new approach to calculating core losses in the SRM

A new approach to calculating core losses in the SRM