Iron Core Losses Research Articles

Research Progress of Fe-based Amorphous / Nanocrystalline Alloys

Fe-based amorphous/nanocrystalline soft magnetic alloys are widely used in high-tech fields such as communications and computers due to their advantages of high saturation magnetic induction, magnetic permeability, resistivity, low coercivity, and iron core loss. This article briefly introduces the preparation process of Fe-based amorphous alloys, highlights the classification and application of Fe-based amorphous/nanocrystalline materials, and the effects of various alloying elements on their organization and performance, and points out the Fe-based amorphous/nanocrystalline possible research trends of alloys.

An Accurate Efficiency Calculation of Self-excited Induction Generator Including Effects of All Machine Parameters

In this paper an accurate method for efficiency calculation of self-excited induction generator (SEIG) at different operating conditions is proposed, considering the effect of stator and rotor iron core losses, stator and rotor circuits stray load losses, stator and rotor winding (copper) losses, mechanical losses, skin-effect losses, and skew-effect losses. The proposed procedure of efficiency calculation is based on the conventional machine tests such as no-load test, load test at variable supply voltage and temperature test without additional measurements. From these conventional tests, all the SEIG losses can be calculated accurately by their related formulas derived based on the SEIG equivalent circuit. The reduction of these losses causes an increase in the SEIG percentage efficiency, and this is a very important feature in electric energy saving by minimization of SEIG equivalent circuit components.

Loss estimation, thermal analysis, and measurement of a large‐scale turbomolecular pump with active magnetic bearings

Temperature rise subjected to the copper losses and iron losses is an important issue for a magnetically suspended turbomolecular pump (MSTMP). In this study, the loss estimation, thermal analysis, and temperature rise measurement of a large-scale MSTMP are investigated. The copper losses and the iron core losses of two radial magnetic bearings, a thrust magnetic bearing, and a brushless direct current motor (BLDCM) are predicted by the analytical models. Based on the predicted loss values, the heat generation rates in the different parts of the large-scale MSTMP are calculated, then the thermal field of the prototype is analysed by the 3D finite-element model. The maximum temperatures estimated for the rotor part and stator part are located at the rotor sleeve and the winding end of BLDCM, which are 68.5 and 55.2 °C, respectively. The loss calculation and thermal field prediction is validated by the temperature rise test in a prototype of large-scale MSTMP with pumping speed of 4100 L/s, ultimate vacuum of 1.8 × 10−7 Pa, and rated speed of 21,000 r/min. The maximum error between the estimated and the measured temperature rise values is <5%.

Analytical prediction of initiation of ferroresonance modes

This research focuses on the impact of basic circuit parameters to the initiation of characteristic ferroresonance modes, which is a non-linear phenomenon, in single-phase power transformers. This non-linear phenomenon is investigated using an equivalent circuit of the transformer together with a circuit simulation. The basic circuit parameters investigated were iron core loss, circuit capacitance, and the source voltage. A mathematical method is used to calculate the critical boundary values of each parameter to avoid the occurrence of ferroresonance in the system. In this paper, an analytical method was used to predict the occurrence of ferroresonance while Matlab/Simulink simulation was used to determine the different ferroresonance modes in the power transformers. By varying the circuit parameters, different ferroresonance modes are observed and discussed.

An Accurate Iron Core Loss Model in Equivalent Circuit of Induction Machines

Iron core loss is the major loss in electrical machines. It performs up to 25% of total machine losses. The machine efficiency calculation requires an accurate prediction of losses. The accuracy of losses calculation depends largely on the equivalent circuit parameter determination and measurements. In this paper, an accurate procedure of iron core loss determination considering the variation effect of supply voltage, iron core temperature, rotor parameters due to skin effect, and magnetizing saturation. The iron core resistance is performed as main component in the equivalent circuit. This resistance is a function of supply voltage and used to calculate part of stray loss as well as iron core loss. The theoretical model is compared with practical results with high accuracy, which proves the validity of the proposed procedure.

Magnetic Field Characteristics and Stator Core Losses of High-Speed Permanent Magnet Synchronous Motors

This study focuses on the core losses in the stator region of high-speed permanent magnet synchronous motors, magnetic field characteristics in the load region, and variations in iron losses caused by changes in these areas. A two-pole 120 kW high-speed permanent magnet synchronous motor is used as the object of study, and a two-dimensional transient electromagnetic field-variable load circuit combined calculation model is established. Based on electromagnetic field theory, the electromagnetic field of the high-speed permanent magnet synchronous motor under multi-load conditions is calculated using the time-stepping finite element method. The magnetic field distribution of the high-speed permanent magnet synchronous motor under a multi-load condition is obtained, and the variations in iron core losses in different parts of the motor under multi-load conditions are further analyzed. The calculation results show that most of the stator iron core losses are dissipated in the stator yoke. The stator yoke iron loss under the no-load condition exceeds 70% of the total stator iron core loss. The stator yoke iron loss under rated operation conditions exceeds 50% of the total stator iron core loss. The stator loss under rated load operation conditions is higher than that under no-load operation. These observations are sufficient to demonstrate that the running status of high-speed motors is closely related to the stator iron losses, which have significance in determining the reasonable yoke structure of high-speed and high-power motors and the cooling methods of motor stators.

Multi-Objective Optimization of Electrical Machine Magnetic Core Using a Vanadium–Cobalt–Iron Alloy

The pursue for electrical machines with higher power densities and efficiencies is a constant research topic among the research and industrial communities. This article focuses on the optimization of an electrical machine's magnetic core using a vanadium-cobalt-iron (VaCoFe) alloy to increase its power density and electrical efficiency. This alloy presents, as its main differentiable characteristics, a higher magnetic saturation point, about 2.4 T, but also higher iron core losses than typical silicon-iron (FeSi) materials. In order to study the impact of using this material in electrical machines magnetic cores, this article focuses on the optimization of magnetic cores with two different materials: VaCoFe alloy and a typical FeSi material. The optimizations are done using a genetic algorithm and using the electromagnetic and thermal lumped parameter models to maximize power density, while reducing magnetic core volumes. Results show that the VaCoFe allows the increase of the power density of the magnetic core in about 25% for low frequencies; however, due to its higher iron core losses, for higher frequencies, the advantages of using this new alloy are not clear. Due to temperature limits, for higher frequencies, it is not possible to work on the VaCoFe best magnetic saturation point. Therefore, results show that for low values electrical frequency ranges, this material can outperform the typical FeSi, while for higher ones, the VaCoFe can be outperformed by the FeSi.

A New Approach Integrated Magnetics Double-Frequency DC/DC Converter

Double-frequency DC/DC converter can improve switching frequency and reduce switching loss than single-frequency DC/DC converter. However, it is heavy and large due to its small high-frequency inductor and large low-frequency inductor. In this article, based on the study on the magnetic integration of the double-frequency DC/DC converter, a novel magnetic integration method was proposed to integrate two inductors with different working frequencies into an EE magnetic core. The proposed magnetic integration scheme is attractive: It outperforms the discrete magnetic double-frequency DC/DC converter in the weight and volume reduction of the magnetic components, the power density improvement of the converter and cost reduction. Compared with the existing solutions of integrated magnetic double-frequency DC/DC converter, this method can further increase the power density of the converter, and reduce the saturation of the magnetic integration components, thereby reducing the iron core loss, as well as improving the dynamic response of the low frequency cell and hence reduce the switching loss. A 150W integrated magnetic double-frequency DC/DC converter was made based on the proposed method, which has been verified by experiments.

Prediction of Eddy Current Losses in Cooling Tubes of Direct Cooled Windings in Electric Machines

The direct coil cooling method is one of the existing cooling techniques for electric machines with concentrated windings, in which cooling tubes of conductive material are inserted between the windings. In such cases, eddy current losses are induced in those cooling tubes because of the time variant magnetic field. To compute the cooling tubes losses, either a transient finite element simulation (mostly based on commercial software), or a full analytical method, which is more complex to be constructed, is required. Instead, this paper proposes a simple and an accurate combined semi-analytical-finite element method to calculate the losses of electric machines having cooling tubes. The 2D magnetostatic solution of the magnetic field is obtained e.g., using the free package “FEMM”. Then, the eddy current losses in the tubes are computed using simple analytical equations. In addition, the iron core losses could be obtained. In order to validate the proposed method, two cases are investigated. In Case 1, a six-toothed stator of a switched reluctance machine (SRM), without rotor, is employed in which six cooling tubes are used while in Case 2 a complete rotating SRM is studied. The proposed method is validated by a 2D transient simulation in the commercial software “ANSYS Maxwell” and also by experimental measurements. Evidently, the proposed method is simple and fast to be constructed and it is almost free of cost.

A Simple and Efficient Quasi-3D Magnetic Equivalent Circuit for Surface Axial Flux Permanent Magnet Synchronous Machines

This paper presents a simple and efficient magnetic equivalent circuit (MEC) model for surface axial flux permanent magnet synchronous machines. The MEC model is used to solve all the electromagnetic properties of the machine including the no load, full load voltages, cogging torque, torque ripple, and stator iron core losses. Moreover, this approach can be extended for all surface permanent magnet synchronous machines. The main novelty of this approach is the development of a static system, which accounts for the rotation. The model takes into account the rotor rotation via time-dependent permanent magnet magnetization sources. The static system matrix facilitates a very fast solving. In addition, to take into account the three-dimensional (3-D) effect, a multislicing of the machine in the radial direction is done. This boosts the simulation time to only 60 s for six slices and 50 time steps including the nonlinear behavior of the stator elements with a great accuracy. Additionally, the number of elements in the MEC can be adjusted to reduce the computational time. This model is verified by means of 3-D and two-dimensional (2-D) multislice finite-element models. In addition, experimental validations are also provided at the end.

FEM Analysis of Iron Core Losses in Magnetically Controlled Shunt Reactor with Distributed Magnetic Valves

In this paper, the MCR with distributed magnetic valves is proposed. The magnetic valve is equally distributed in iron core, which is piled up by silicon-steel sheets and epoxy sheets. Field-circuit coupled simulation model is established in ANSYS software. The wave forms of electrical state variables, magnetic flux density distribution and iron core losses are acquired. The comparison with the MCRs with a single-stage magnetic valves and multiple-stage magnetic valves demonstrates the advantage of proposed magnetic valve structure.

Flux and Loss Distribution in Iron Cores With Hybrid T-Joint

Local high iron loss may occur due to the deviation of magnetic flux from the rolling direction of electrical steel in the T-joint area of the transformer core. In this paper, to reduce the iron core loss in the T-joint region, a hybrid iron core model using nonoriented and grain-oriented magnetic materials is proposed. Three-dimensional magnetic field analysis considering the nonlinearity and laminated structure of the original and proposed iron core models is carried out by using the finite element analysis. The flux and iron loss distributions of the original and the hybrid cores are compared. The results show that approximately 2% iron loss reduction can be achieved by using the proposed hybrid structure.

Simulation of Three-Phase Salient Pole Generator under Operating Conditions

The three-phase synchronous generators are still the backbone of most electric power plants in the world. Many researchers still study synchronous generators in attempts to improve their performance and reduce losses in iron core, copper windings, friction ball bearings, and moments of inertia due to mass and rotor diameter. One of the important characteristics studied insynchronous generator behavior is the generator’svoltage regulation (VR%). Over the past century, researchers have developed four practical and mathematical methods to determine the value of the combined voltages of synchronous generators. This article describes a new method based on the impedance method, the magneto motive force (MMF) method, and the Potier method. The new method effectiveness evaluation is conducted via calculating the four methods and their application to a synchronous generator. The article also offers practical and theoretical recommendations to improve the results and increase flexibility in changing loads as their power factors change.

Analytical Prediction of Iron-Core Losses in Flux-Modulated Permanent-Magnet Synchronous Machines

In this paper, an analytical approach allowing the prediction of iron-core losses in flux-modulated permanent-magnet synchronous machines. According to the Maxwell–Fourier method (viz., the multi-layer model) and Cauchy’s product theorem, the magnetic field distribution is determined in different parts of machine by considering the iron permeability on the basis of solving both Poisson’s and Laplace’s equations. Next to the dc bias flux density and the minor hysteresis loops, which are taken into account, the Bertotti’s model and the flux variation locus are employed to calculate the iron-core losses under load and no-load conditions in post-processing from the magnetic field analytical calculation. Finally, in order to validate the proposed analytical method, the results are verified by the comparison with the finite-element method. The comparisons show good results of the proposed model.

Hierarchical thermal network analysis of axial‐flux permanent‐magnet synchronous machine for electric motorcycle

A novel 24 kW 12-slots/10-poles axial-flux permanent-magnet synchronous machine (AFPMSM) with external rotor motor applied to the large electric motorcycle is introduced in this study, which has the characteristics of the yokeless and segmented armature for power density improvement. The hierarchical method is used for calculation of stator iron core loss based on the analytical solution of air-gap flux density, which cuts the prototype into many equivalent linear motor slices in the circumferential direction. A major advantage of hierarchical methods over traditional iron core loss calculation is its higher accuracy and rapidity. Then a lumped parameter T-type thermal network model is presented for AFPMSM temperature rise calculation. A 3D liquid–solid coupling model is compared with the 2D T-type lumped parameter thermal network. Finally, a temperature rise measurement platform is established to verify the above-mentioned methods. Testing result shows that the hierarchical method and T-type thermal network have a higher accuracy to predict each part temperature.

A New Multi-Conductor Transmission Line Model of Transformer Winding for Frequency Response Analysis Considering the Frequency-Dependent Property of the Lamination Core

Multi-conductor transmission line (MTL) model of power transformer winding for frequency response analysis (FRA) has been successfully applied for the purpose of studying the characteristics of winding deformations. Most of the time it is considered that, at a frequency above 10 kHz, the flux does not penetrate the core, and the iron core losses due to hysteresis and eddy current can be neglected accordingly. However, in fact, there is still a little flux residing in the core, and it has a significant influence on inductances and resistances of transformer winding even up to approximately 1 MHz. In this paper, by introducing the anisotropic complex permeability of the lamination core into calculating inductances and resistances of the MTL model, a new MTL model considering the frequency-dependent property of the lamination core for FRA is presented. In addition, the accuracy and effectiveness of the MTL model are validated by means of a comparison between measured and emulated FRA results in a wide frequency range from 10 Hz up to 10 MHz. This precise MTL model of the transformer winding provides us a more objective and positive condition for simulation research of winding deformation detection.

Optimising the transformer substation topology in order to minimise annual energy losses

The transformer losses can usually be classified into two basic categories: losses in the transformer core (voltage-dependent losses) and losses in the transformer winding copper (current-dependent losses). By increasing the number of active transformers in the transformer substation the authors reduce the total losses in the transformer copper but on the other hand increase the total losses in the transformer iron core. Considering this, it can be concluded that it is possible to determine the optimum number of active transformers in the substation for each operating condition together with the way they are connected. In this study, the authors propose a novel optimisation algorithm which can be used to determine the optimal operating conditions of the transformer substation to minimise annual energy losses while avoiding frequent transformer switching and assuring provision of sufficient transformation power in order to supply distribution load. The algorithms which are outlined are applicable for substations 110/xkV and 35/10(20)kV which have more than one transformer installed with different levels of substation topology complexity (flexibility).

Steady and dynamic states analysis of induction motor: FEA approach

This paper deals with the steady and dynamic states analysis of induction motor using finite element analysis (FEA) approach. The motor has aluminum rotor bars and is designed for direct-on-line operation at 50 Hz. A study of the losses occurring in the motor performed at operating frequency of 50Hz showed that stator copper loss and rotor copper loss were higher than the other types of losses like the stray, iron core, frictional and windage losses. The motor efficiency based on material design was also studied at operating temperature. The materials considered in this paper are iron, nickel and cobalt. It was observed that iron at 75°C provided the best efficiency than other materials. The steady and dynamic states characteristics of the motor at rated load and on no-load conditions were observed. The flux levels at these loading conditions were also monitored. http://dx.doi.org/10.4314/njt.v36i4.29

Power Loss and Heat Dissipation Characteristics of High-Power Electromechanical Actuators

Due to serious power loss and heating caused by compact volume and high power density of high power electromechanical actuator (EMA), thermal analysis is becoming the key aspects in its design optimization. Numerical calculation method is proposed to calculate the electrical loss, iron core loss and drive chain mechanical loss in EMA. An equivalent thermal network model based on lumped parameters is established, with the acquisition of heat transfer matrix equation of all network nodes. Temperature rise of each part of the EMA is obtained by solving the equation. By comparison of simulated temperature rise in rated operating condition with test results, the accuracy of the model is verified. Then temperature rise simulation of EMA under simulated actual flight condition is carried out, with the results showing positive guidelines in the optimization design of EMA systems.

A Motor Efficiency Measurement System Design Based on Loss Segregation Method

There are many methods about efficiency measurement for introductive motors in international standards, among which the loss segregation method assumes that the stray loss and iron core loss can be treated as constants, and then the process of efficiency estimation can be simplified. This paper designed a motor efficiency measurement system based on loss segregation method. It’s a calculation module based on a micro-processor. The motor current is the only variable for motor efficiency calculation, this system can calculate and read the result on-line. The deviation between the loss segregation method and the direct method is very small.