Iron Loss Calculation Research Articles

Thermal Design of High-Energy-Density Wound Components

This paper presents an alternative computationally efficient approach to the thermal design of compact wound components. The method is based on the use of anisotropic lumped regions within 3-D thermal finite-element analyses. The lumped regions replicate the multimaterial composites used in the construction of wound components. Material data for these lumped regions are obtained experimentally, accounting for the thermal anisotropy. Input loss data for the analysis were derived by combining electromagnetic finite-element iron loss calculations with experimental ac copper loss correlations. The technique is applied to a design of a high-energy-density filter inductor. Thermal measurements from prototype inductors are compared with the theoretical predictions showing a good agreement.

Calculation of iron loss in rotating machines by direct consideration of eddy currents in electrical steel sheets

AbstractA method for calculation of iron loss in rotating machines is proposed. The calculation employs the finite element method while taking into consideration the eddy currents in electrical steel sheets. First, the electromagnetic field distribution and iron loss of several types of electrical steel sheets are calculated by the proposed method, formulated as a one‐dimensional model. The results are compared with those of experiments and the conventional method in order to verify the validity of the proposed method. The influence of the skin effect and magnetic saturation in the electrical steel sheets on the iron loss characteristics is also investigated. Next, the proposed method formulated as a three‐dimensional model is applied to several types of rotating machines. It is shown that the skin effect is significant in the case of high‐frequency harmonic fields and that direct consideration of eddy currents by the finite element method is indispensable in such cases. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(3): 69–80, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21053

Application of new tools in the thermal behavior study of electrical machines

Economic, competitive or energy efficiency factors require designing smaller and more efficient machines that pose greater demands on its design. This, coupled with the need to reduce time and production costs requires the use of simulation software as basic design tool. One of these requirements is to know the thermal behaviour of the machine, subject on which this paper focuses. Based on the electromagnetic study of permanent magnet synchronous machine (PMSM), performed using finite elements, a special attention is given to the calculation of iron losses that are later used to simulate its thermal behaviour. The results are compared with those obtained in real tests of the machine on steady states allowing validate the method, to later on, analyse the transient behaviour of the machine.

Dynamic Finite Element Hysteresis Model for Iron Loss Calculation in Non-Oriented Grain Iron Laminations Under PWM Excitation

This paper introduces a dynamic finite element model for calculating iron loss in ferromagnetic non-oriented grain laminations under pulse-width modulation (PWM) excitation. The proposed methodology accounts for static hysteresis, classical eddy currents and anomalous losses and has been validated by measurements in Epstein device in different cases of PWM voltage waveforms. The model is based on a particular 2-D finite-element technique by using standard static iron lamination characteristics and offers sufficient accuracy in all studied cases.

Loss Evaluation of an Induction Motor Model Core by Vector Magnetic Characteristic Analysis

This paper presents results of iron-loss evaluation of an induction motor model core by using the finite element method considering two-dimensional vector magnetic properties. We propose a new iron-loss calculation method considering higher harmonic components of the flux density waveforms caused by the secondary slot ripples. Influence of the harmonic components on the total iron loss is clarified numerically. In addition, reduction of rotational iron losses is investigated by making holes at the tooth base parts. The results show that the rotational magnetic flux distribution is effectively controlled by making holes. In this paper, obtained knowledge about iron-loss control with holes in the stator core is presented and discussed.

Iron and Magnet Losses and Torque Calculation of Interior Permanent Magnet Synchronous Machines Using Magnetic Equivalent Circuit

We present a faster and simpler approach for the calculation of iron and magnet losses and torque of an interior permanent-magnet synchronous machine (IPMSM) than finite-element methods (FEM). It uses a magnetic equivalent circuit (MEC) based on large elements and takes into account magnetic saturation and magnet eddy currents. The machine is represented by nonlinear and constant reluctance elements and flux sources. Solution of the nonlinear magnetic circuit is obtained by an iterative method. The results allow the calculation of losses and torque of the machine. Due to the approximations used in the formulation of the MEC, this method is less accurate but faster than nonlinear transient magnetic FEM, and is more useful for the comparison of different machine designs during design optimization.

Iron Loss Model for Rotating Machines Using Direct Eddy Current Analysis in Electrical Steel Sheets

In this paper, we propose and validate a method for the accurate estimation of iron loss in rotating machines. In this method, the eddy current loss in electrical steel sheets is directly calculated by nonlinear time-domain electromagnetic field analysis with a simple approximation of the excess loss. The hysteresis loss is also estimated by considering the flux distribution along the thickness of the steel sheet. The advantage of the method is that the high-frequency harmonic losses can be calculated accurately using only few material constants. The validity of this method is confirmed by experiments performed on a ring specimen and several types of motors. The experimental and calculated iron losses in each experiment are found to be in good agreement. It is clarified that the proposed method is useful for the accurate estimation of higher order harmonic losses, particularly, carrier losses caused by inverters.

Shape Optimization of Rotating Machines Using Time-Stepping Adaptive Finite Element Method

A time-stepping adaptive finite element method is proposed for shape optimization of rotating machines. In the proposed method, different mesh-generation procedures are applied to the core and the other regions for the purpose of the iron-loss calculation. A technique for automatically separating and connecting the stator and rotor meshes is also introduced for the rotation of the rotor. The proposed method is applied for shape optimizations of permanent magnet motors to achieve the loss reduction. The necessity and usefulness of the proposed method are verified.

A Study on Loss Characteristics of IPMSM for FCEV Considering the Rotating Field

This paper presented the loss characteristics of interior permanent-magnet machines (IPMSM) for a fuel-cell electric vehicle. In order to study the loss characteristics of the machine, one prototype machine having 100 [kW] was designed. In the analysis, to consider the harmonic magnetic field and the rotational variation of flux vectors in the core of the machine effectively, we proposed a new harmonic iron-loss calculation method based on adaptive loss coefficients. To verify the performance of the proposed method, we calculated a no-load iron loss in an IPMSM with conventional methods. Then, the estimated iron losses were compared with the experimental data. It was clarified that the proposed method is more effective than conventional methods at high-speed operation. Based on this proposed method, we investigated the losses of the machine considering operating points according to its speed. From the results, it was shown that the main loss component and the location of iron-loss distribution change depending on operating condition.

Method for estimating core losses in switched reluctance motors

SUMMARY The prediction of switched reluctance motor (SRM) performance requires knowledge of core losses. However, the calculation of iron losses in SRM is especially complex first because the flux waveforms are nonsinusoidal and different parts of the magnetic circuit have different waveforms and second because they are conditioned by the type of control used. This study proposes an analytical method for calculating core losses that comprises simulation of the SRM using finite element analysis to determine the magnetization curves, and SRM modeling, which enables transient simulations with the associated electronic power converter run under different control strategies. The flux density waveforms in the different parts of the SRM are derived from the flux density waveform of the stator pole that is obtained from the transient simulation. The specific core losses (in W/kg) are separated into three parts (hysteresis losses, classical eddy current losses and excess losses) and calculated using the waveforms and time derivatives of the local flux density. The core losses for each part of the SRM’s magnetic circuit can be estimated using the calculated values for specific hysteresis losses, specific classical eddy current losses and specific excess losses for each zone. Adding these individual losses yields the total core losses. The method was applied to three-phase 6/4 SRM, and the calculated results were compared with experimentally obtained measurements. Copyright # 2010 John Wiley & Sons, Ltd.

Iron Loss Analysis Considering Excitation Conditions Under Alternating Magnetic Fields

In this paper, the nature of iron loss in electrical steel during alternating field excitation is investigated more precisely. The exact definition of AC iron loss is cleared by accurately measuring the iron loss for conditions of both the sinusoidal magnetic field and sinusoidal magnetic flux density. The results of this approach to iron loss calculations in electrical steel are compared to experimentally-measured losses. In addition, an inverse hysteresis model considering eddy current loss was developed to analyze the iron loss when the input is the voltage source. With this model, the inrush current in the inductor or transformer as well as the iron loss can be calculated.

Iron Loss Calculation in a Three-Phase-Laminated-Core Variable Inductor Based on Reluctance Network Analysis

Variable inductors, which consist of only a magnetic core and primary dc and secondary ac windings, can control effective inductance of the secondary ac winding by primary dc excitation. Therefore, the variable inductors can be applied as a var compensator in electric power systems. In a previous paper, we have proposed a novel three-phase-laminated-core variable inductor. It has only one laminated core in which the three-phase secondary ac windings are installed to reduce size and weight in comparison with a conventional single-phase variable inductor. Good controllability and sinusoidal output current of the proposed variable inductor were demonstrated. This paper presents a method for calculating iron loss of the three-phase-laminated-core variable inductor based on reluctance network analysis (RNA). The validity of the proposed method is proved by comparing with measured values.

Harmonic Iron Loss Analysis of Electrical Machines for High-Speed Operation Considering Driving Condition

In this paper, we proposed new harmonic iron loss calculation methods for electrical machines. The new methods based on the concept of variable loss coefficients due to their flux density and frequency estimate harmonic iron loss in the time domain and the frequency domain. In order to verify the performance of the proposed method, we calculated the iron loss with conventional methods. Then, the estimated iron losses were compared with the experimental data. It was clarified that the proposed methods are more effective than the conventional methods at high-speed operation. Based on these newly proposed methods, we analyzed the iron loss of the machine for electric vehicle (EV) according to its driving condition. From the analysis results, it was shown that the harmonic iron losses of stator are larger than before at field-weakening region. In addition, it was revealed that rotor iron loss mainly induced by stator slot ripples does not show strong dependence on the current angle and only varied primarily according to the speed.

A Practical Iron Loss Calculation for AC Filter Inductors Used in PWM Inverters

A novel iron loss calculation method is proposed based on an iron loss map for an AC filter inductor used in a pulsewidth-modulation (PWM) inverter. The iron loss map, previously reported by the authors, is created by measuring the dynamic minor loop on the B-H plane, and this is used for the calculation of inductor iron loss in the dc chopper circuit. However, in the case of an AC filter inductor used in a PWM inverter, the iron loss map cannot be directory applied to the iron loss calculation. In this paper, an iron loss calculation for an ac filter inductor is presented by expanding the loss map method. We describe the principle of expansion and the practical procedure for the calculation, which utilizes the loss map and a conventional circuit simulator. Iron loss for the ac filter inductor under some typical modulation methods of the PWM inverter are calculated and discussed with regard to the relation between the modulation methods and iron loss. The calculated results are verified using experimental results from a 500-W inverter setup. The inductor loss and conversion efficiency of the PWM inverter are measured for each modulation method.

Parameter Prediction and Modelling Methods for Traction Motor of Hybrid Electric Vehicle

This paper introduces the parameter prediction and modelling methods for the traction motor of hybrid electric vehicle (HEV). In the general HEV simulation, the traction motor is mainly defined by efficiency map and torque/speed curve. Therefore, this paper will focus on the prediction of these parameters, which involves the numerical analysis on the motor inductances calculation, iron-loss resistance calculation, and characteristic estimation algorithm and so on. The modelling method is split into tow major parts: configuration of model and composing graphic user interface (GUI). An experiment result will be used to compare with the calculated efficiency map to verify the validity of these methods. In addition, the model construction will be explained by flowcharts. Considering popularity, the MATLAB/Simulink will be used to construct the simulation program. And a GUI will be designed and used to show the simulation results. With the other models of vehicle components, the simulation will be processed in a parallel-type HEV model in an urban road condition (FTP72), and the simulation results will be shown in the end of this paper.

A Research on Iron Loss of IPMSM With a Fractional Number of Slot Per Pole

In this paper, we investigated rotor iron loss of interior permanent magnet synchronous machine (IPMSM), which has distributed armature windings. In order to study the iron loss with the effect of slot-pole combination, two machines for high-speed operation such as electric vehicle were designed. One is fractional slot winding and the other is conventional one. In the analysis, we developed a new iron loss model of electrical machines for high-speed operation. The calculated iron loss was compared with the experimental data. It was clarified that the proposed method can estimate iron loss effectively at high-speed operation. Based on this newly proposed method, we analyzed iron loss of the two machines according to their driving conditions. From the analysis results, it was shown that rotor iron loss of machine employing fractional slot-winding is definitely large at load condition. In addition, it is interesting that the ratio (rotor iron loss/stator iron loss) becomes larger as the speed of the machines increase if the number of slot per pole is fractional.

Loss Analysis of a Reactor under Inverter Power Supply Taking Account of Anomalous Eddy Current Loss

To reduce the iron losses of reactors under inverter power supply, the loss was calculated by using magnetic field analysis, which models a laminated core by combining a 3D solid-core model with a 1D steel plate model, using the finite element method (FEM). In this method, the structure of the laminations and the eddy currents in the steel plates can be taken into account. However, for reactors driven by inverter power supply, the calculated iron losses are much smaller than the measured results, because the anomalous eddy current loss induced by domain wall motion in the steel plates is neglected in the loss calculation. Therefore, this paper investigates a simple numeric modelling method that takes account of the anomalous eddy current loss by modifying the conductivity of the steel plates. First, the method is verified by comparing the calculated iron loss of one sheet of steel plate with the measured data. The method is then applied to the loss calculation of reactors under inverter power supply. The differences between the calculated and measured results become smaller when the anomalous eddy current loss in the steel plates is taken into account.

鉄心内部の応力分布を考慮した高精度鉄損解析手法

鉄心内部の応力分布を考慮した高精度鉄損解析手法

A Simplified Iron Loss Model for Laminated Magnetic Cores

This paper presents a new method for the prediction of iron losses in laminated magnetic cores. The method is based on the evaluation of the magnetization curves and loop shapes by which the iron losses, including hysteresis, excess, and classical eddy-current losses, are calculated from the loop area. The purpose of the method is to omit the numerical solution of the nonlinear diffusion equation (resulting from Maxwell equations) while maintaining reasonable accuracy of the iron losses. Therefore, the proposed method determines, using simple concepts, three magnetic field strength components that are responsible for generating the iron losses. The magnetic field component of the hysteresis loss is calculated by a static hysteresis model. The magnetic field component of the excess loss is calculated using the statistical loss theory. Determining the magnetic field component of the classical eddy-current loss is based upon the assumption that the flux distribution in the steel sheet is uniform, but, here, the eddy-current loss is implicitly enforced to be dependent on the magnetic characteristics of the material. The proposed method is applied to the calculation of iron losses in an electrical steel when the accuracy, stability, and generality of the method are discussed.

The impact of different stator and rotor slot number combinations on iron losses of a three-phase induction motor at no-load

The electromechanical characteristics of induction motors depend on the used stator and rotor slot combination. The correlation between the usage of different stator and rotor slot number combinations, magnetic flux density distributions, no-load iron losses and rated load winding over-temperatures for a specific induction motor is presented. The motor's magnetic field was analyzed by traces of the magnetic flux density vector, obtained by FEM. Post-processing of FE magnetic field solution was used for posterior iron loss calculation of the motor iron loss at no-load. The examined motor stator lamination had 36 semi-closed slots and the rotor laminations had 28, 33, 34, 44 and 46 semi-closed slots.