Iron Loss Model Research Articles

Loss Minimization of an Electrical Vehicle Machine Considering Its Control and Iron Losses

In this paper, optimization of the control of an electrical machine allowing a minimization of its total losses is described. It is based on the use of an iron loss model [loss surface (LS) model] coupled to the electromagnetic finite-element simulations of the machine. The LS model is a scalar and dynamic hysteresis model developed many years ago at G2Elab and tested for iron loss prediction in several cases of electric machines. It is first characterized and improved in this paper for M330-35A SiFe sheets. Then, it is associated with a finite-element analysis to compute, in a post-processor mode, the local and global magnetic losses in the machine. For electric vehicle application, the whole torque–speed variation should be investigated. To do that, a quick response surface is constructed from a small number of simulations and the iron loss is determined. Then, a suitable optimization algorithm is developed. This approach is then illustrated by a case study and compared with classical optimization in which only the copper losses in conductors are considered. Gains of up to 50% reduction in the total losses of the machine in certain operating areas are observed.

New Approach for Accurate Prediction of Eddy Current Losses in Laminated Material in the Presence of Skin Effect With 2-D FEA

Two-dimensional finite element (FE) models normally assume the laminated core as a non-conductive material, and therefore, the damping effect of the eddy currents is ignored in the field solution. Besides, the use of integrated iron loss models in FE software could result in overestimated eddy current losses at high frequencies if the skin effect is ignored. This paper presents a simple way to accurately predict eddy current losses in laminations with FE analysis. An experimental setup along with the simulation models is used to demonstrate the validity of the method. The utility of this method in loss separation and identification of loss coefficients in the presence of skin effect is also illustrated. This method is also applied to a synchronous permanent magnet (PM) machine with sinusoidal current.

Implementation of Iron Loss Model on Graphic Processing Units

Design engineers are always looking for extra computational power to speed up the execution of their tasks. One way to achieve this speedup is to identify tasks with a high degree of parallelism and process them with graphic processing units (GPUs). GPUs are optimized to process such tasks efficiently and quickly in massive multicore hardware. The steps involved in a finite-element (FE) electromagnetic simulation are computationally very expensive. One such step is the communication between FE solver and the material loss model that takes place for all the elements in the mesh for each time step. This task is massively parallel and, thus, could be executed in a GPU. As an example, a physics-based material model, the Jiles–Atherton model, is implemented in a GPU to compute the $B$ – $H$ hysteretic relationship, which can be directly incorporated in FE simulations. The performance of the GPU is compared with that of the given microprocessor in terms of computational time. A time gain of 13.8 times has been achieved.

Operating point resolved loss computation in electrical machines

AbstractMagnetic circuits of electromagnetic energy converters, such as electrical machines, are nowadays highly utilized. This proposition is intrinsic for the magnetic as well as the electric circuit and depicts that significant enhancements of electrical machines are difficult to achieve in the absence of a detailed understanding of underlying effects. In order to improve the properties of electrical machines the accurate determination of the locally distributed iron losses based on idealized model assumptions solely is not sufficient. Other loss generating effects have to be considered and the possibility being able to distinguish between the causes of particular loss components is indispensable. Parasitic loss mechanisms additionally contributing to the total losses originating from field harmonics, non-linear material behaviour, rotational magnetizations, and detrimental effects caused by the manufacturing process or temperature, are not explicitly considered in the common iron-loss models, probably even not specifically contained in commonly used calibration factors. This paper presents a methodology being able to distinguish between different loss mechanisms and enables to individually consider particular loss mechanisms in the model of the electric machine. A sensitivity analysis of the model parameters can be performed to obtain information about which decisive loss origin for which working point has to be manipulated by the electromagnetic design or the control of the machine.

Loss Prediction and Thermal Analysis of Surface-Mounted Brushless AC PM Machines for Electric Vehicle Application Considering Driving Duty Cycle

This paper presents a computationally efficient loss prediction procedure and thermal analysis of surface-mounted brushless AC permanent magnet (PM) machine considering the UDDS driving duty cycle by using a lumped parameters’ thermal model. The accurate prediction of loss and its variation with load are essential for thermal analysis. Employing finite element analysis (FEA) to determine loss at every load point would be computationally intensive. Here, the finite element analysis and/or experiment based computationally efficient winding copper and iron loss and permanent magnet (PM) power loss models are employed to calculate the electromagnetic loss at every operation point, respectively. Then, the lumped parameter thermal method is used to analyse the thermal behaviour of the driving PM machine. Experiments have been carried out to measure the temperature distribution in a motor prototype. The calculation and experiment results are compared and discussed.

Modeling of Temperature Effects on Magnetic Property of Nonoriented Silicon Steel Lamination

This paper proposed a temperature-dependent iron loss model and corresponding dynamic hysteresis model, where temperature coefficient ${k}$ is introduced to consider the thermal effect on eddy-current loss. The iron loss model is validated by massive experimental measurement of test samples, 1174 combinations of various temperatures, magnetic inductions, and frequencies for nonoriented silicon steel specimen. The relative error of the model is $\sim 11$ % in a wide range of 50–400 Hz, 26 °C–200 °C, and 0–2 T. The proposed method can be applicable to other types of magnetic materials as long as whose resistivity rate exhibits approximately linear thermal dependence within a temperature range of 26 °C–200 °C.

The Effect of Common-Mode Voltage Elimination on the Iron Loss in Machine Core Laminations of Multilevel Drives

This paper studies the effect of common-mode voltage elimination (CMVE) on the iron loss of electrical machine core laminations under multilevel converter supply. Three identical magnetic ring cores are excited by either a three-level converter or a five-level voltage source converter to study the behavior of CMVE on a three-phase system. Both multilevel converters are controlled by using a space vector pulsewidth modulation as it is one of the most often used techniques for CMVE. These experimental results are confirmed numerically with a dynamic iron loss model. In addition, the effect of CMVE, at different switching frequencies, on the core loss of a synchronous machine is numerically studied. The results presented in this paper show that the core loss is considerably increased when the CMVE is implemented. However, this iron loss increase in the five-level drive systems is lower compared with the three-level ones. Therefore, it is important that the designers of drive systems take such effects into consideration.

Maximum Efficiency per Torque Direct Flux Vector Control of Induction Motor Drives

In this paper, a loss-minimizing strategy is proposed for induction motor drives to ensure maximum efficiency operation for a given torque demand. The proposed strategy directly regulates the machine stator flux, according to the desired torque, using an optimal stator flux reference. Therefore, the proposed strategy is suitable for motor control schemes that are based on direct flux regulation, such as direct torque control or direct flux vector control. The maximum efficiency per torque (MEPT) stator flux map is computed offline using the traditional no-load and short-circuit test data. An iron loss model based on the stator flux and frequency is also proposed for the calibration of the machine loss model and also for online monitoring of the iron losses during motor operation. The proposed MEPT strategy has been validated on a 2.2-kW induction machine, and the motor efficiency has been measured for different speed values and variable load conditions. The experimental results confirm the effectiveness of the proposed solution.

Iron Loss Analysis of Doubly Salient Brushless DC Generators

The doubly salient electromagnetic machine (DSEM) is a kind of variable reluctance machine, which is different from the conventional ac electric machines. A new 24/16-pole DSEM is presented, and the configuration and operation principle are discussed. Based on the comprehensive study of the field distribution feature, the DSEM is separated into eight sections to investigate the iron loss distribution. In order to predict the iron loss of the doubly salient electromagnetic generator (DSEG), the flux density variations of each section are resolved into radial and circumferential waveforms, and Fourier transform is utilized in consideration of harmonic components. A calculation model of iron loss is established, and the coefficients are determined by the measured data at different speeds. The iron loss distribution of the DSEG is investigated. The proportion of iron loss to copper loss is further analyzed under different load conditions. Moreover, the influences of speed, air-gap length, and field current on iron loss are analyzed and summarized. Finally, the calculation and analysis of iron loss are verified by experimental results.

Identification of Synchronous Machine Magnetization Characteristics From Calorimetric Core-Loss and No-Load Curve Measurements

The magnetic material characteristics of a wound-field synchronous machine are identified based on global calorimetric core-loss and no-load curve measurements. This is accomplished by solving a coupled experimental–numerical electromagnetic inverse problem, formulated to minimize the difference between a finite-element (FE) simulation-based Kriging surrogate model and the measurement results. The core-loss estimation in the FE model is based on combining a dynamic iron-loss model and a static vector Jiles–Atherton hysteresis model, whose parameters that are obtained by solving the inverse problem. The results show that reasonable hysteresis loops can be produced for a grid-supplied machine, while for an inverter-supplied machine the limitations in the FE and iron-loss models seemingly exaggerate the area of the loop. In addition, the effect of the measurement uncertainty on the inverse problem is quantitatively estimated.

Establishing a Relation between Preisach and Jiles–Atherton Models

Hysteresis models can incorporate the effects of operating conditions (frequency, stress, and temperature) on iron losses incurred in ferromagnetic materials. Among such models, the Jiles–Atherton (JA) and Preisach models are the most popular and various modifications of these have been proposed in the literature to model the effect of frequency, stress, and temperature on iron losses. Both of these representations produce accurate results compared with the curve fitting models and can be directly implemented in finite element simulations. Unfortunately, it is very difficult to incorporate all these effects into a single iron loss model that is computationally efficient and can predict iron losses with reasonable accuracy for a given range of these parameters. In this paper, an effort has been made to establish a relationship between JA and Preisach models and an interpolation-based approach is presented to predict iron losses that utilizes the Preisach model on top of the JA model and incorporates all of the above factors. It is shown that iron loss can be predicted accurately for any value of frequency, stress, and temperature.

Comparison of Iron Loss Models for Electrical Machines With Different Frequency Domain and Time Domain Methods for Excess Loss Prediction

The goal of this paper is to investigate the accuracy of modeling the excess loss in electrical steels using a time domain model with Bertotti's loss model parameters n 0 and V 0 fitted in the frequency domain. Three variants of iron loss models based on Bertotti's theory are compared for the prediction of iron losses under sinusoidal and non-sinusoidal flux conditions. The non-sinusoidal waveforms are based on the realistic time variation of the magnetic induction in the stator core of an electrical machine, obtained from a finite element-based machine model.

Influence of Winding Scheme on the Iron-Loss Distribution in Permanent Magnet Synchronous Machines

The influence of the winding scheme [concentrated, single-tooth, distributed (pitched, unpitched)] on the iron-loss distribution in a rotor and stator is to a large extent unknown. At present, windings are primarily selected with respect to back-EMF harmonics and torque fluctuation. In such approaches, the influence of iron losses is disregarded. Moreover, minor loop losses are not covered by most iron-loss models and are therefore ignored. This yields inaccurate results. In particular, for interior permanent magnet machines, the rotor temperature has to be taken into account. For variable-speed drives, losses have to be calculated over the complete operating range. Hence their distribution is studied in this paper for various operating points. The influence of the winding scheme on iron losses and iron-loss distribution is investigated based on finite-element simulations.

Segregation of Iron Losses From Rotational Field Measurements and Application to Electrical Machine

This paper presents a methodology for identifying a novel iron loss model and segregating the different loss components from measurements on a single-sheet tester with alternating and rotating fields. The eddy-current losses are first extracted with a 1-D numerical approach and the hysteresis and excess losses are then estimated with an analytical method that allows the separation of alternating and rotational hysteresis as well as excess losses. The elaborated iron loss model can be applied in case of distorted flux density and on a wide range of frequencies. The identified model is further applied in the time-stepping computation of an induction motor in the view of better estimation and segregation of iron losses. The results of no-load simulations at different voltage levels are in good agreement with the measured ones. All of the presented computations and models were validated experimentally.

Parameter Optimal Choice of Claw Pole Alternator based on Iron Loss Model

Based on classical Berotti discrete iron loss calculation model, the iron loss analysis mathematical model of alternator was proposed in this paper. Considering characteristics of high speed and changing frequency of the alternator, Maxwell 3-D model was built to analyze iron loss corresponding to each running speed in alternator. Based on iron loss model of alternator at rated speed, the rotor claw pole size was made an optimization design. The optimization results showed that alternator's output performance had been improved. A new idea was explored in size optimization design of claw pole alternator.

Three-Dimensional Eddy-Current Analysis in Steel Laminations of Electrical Machines as a Contribution for Improved Iron Loss Modeling

A finite-element method to compute the 3-D eddy-current distribution in steel laminations of electrical machines is presented and applied to the loss estimation of an induction machine. Two different eddy-current formulations, the A-V and A-T formulations, are investigated. The 3-D model is excited by boundary conditions derived from a 2-D field solution. The obtained eddy-current losses serve as a validation basis for those from two simplified iron loss models. The first one is the traditional model based on the statistical loss theory. The second one is the so-called hybrid model, which is based on the evaluation of magnetization curves. Both models are found to produce reasonable results for low-frequency losses. The hybrid model is particularly suitable for the estimation of high-order harmonic losses. The results from the models are compared to measured no-load iron loss data.

Iron-Loss Model With Consideration of Minor Loops Applied to FE-Simulations of Electrical Machines

The accurate prediction of iron losses in soft magnetic materials for various frequencies and magnetic flux densities is eminent for an enhanced design of electrical machines in automotive applications. For this purpose different phenomenological iron-loss models have been proposed describing the loss generating effects. Most of these suffer from poor accuracy for high frequencies as well as high values of magnetic flux densities. This paper presents an advanced iron-loss formula, the IEM-Formula, which resolves the limitation of the common iron-loss models by introducing a high order term of the magnetic flux density. Furthermore the IEM-Formula is extended in order to include the influence of higher harmonics as well as minor loops. In line with this a detailed study of minor loop loss behavior is presented. Exemplarily, the iron-loss formula is utilized to calculate the iron losses of a permanent magnet synchronous machine for the drive train of a full electric vehicle.

Uni- and Bidirectional Flux Variation Loci Method for Analytical Prediction of Iron Losses in Doubly-Salient Field-Excited Switched-Flux Machines

Field-Excited Flux-Switching machines are doubly-salient machines with complex flux-density waveforms in the core. Hence, prediction of iron losses is difficult. In this article, we propose a method to determine flux loci in iron parts in an analytical manner, accounting for bidirectional field in back-irons of stator and rotor. The analytical model for flux-density prediction in the core at no-load was first validated with 2D FE simulations. Then measured iron losses on a prototype machine were used to calibrate an iron loss model. It was shown that in FE-SF machines rotor iron losses are not negligible and represent 28% of total iron losses. This model could be advantageously used in a design optimization procedure.

Three-Dimensional Eddy Current Loss Modeling in Steel Laminations of Skewed Induction Machines

The effects of skewing on the loss behavior of a megawatt rated slip-ring induction machine are studied. The iron loss evaluation is performed by postprocessing the field solution obtained from a multi-slice finite element model. A novel method to compute the three-dimensional eddy current distribution in the steel sheets is employed for the eddy current analysis. The iron loss models are validated against no-load iron loss measurements. Simulation results under load show that skewing leads to a highly non-uniform iron loss distribution along the machine length. The sum of the iron and copper losses increases slightly compared to a machine with straight rotor bars.

Experimental determination and numerical evaluation of core losses in a 150‐kVA wound‐field synchronous machine

The losses in the laminated core of a 150-kVA wound-field synchronous machine are investigated with calorimetric measurements and a numerical iron-loss model for steel laminations. Both grid supply and pulse-width modulated inverter supply with 1 kHz and 6 kHz switching frequencies are studied. The effect of rotor lamination material on total core losses is studied by measuring and simulating the machine with three prototype rotors, the first one being stacked of insulated 0.5-mm Fe–Si sheets and the last two of uninsulated 1-mm and 2-mm steel sheets, respectively. At no load, the losses in the frame of the machine are shown to be extremely significant with voltages above the rated one. The results on load operation show that the additional inverter-induced core losses are significantly larger with the thicker sheets. The rotor eddy-current loss is the most affected component because of loading and the distorted supply voltage. However, unlike expected and predicted by the model, the differences in the losses between the 1-mm and 2-mm rotors are negligible in no-load operation and relatively small also at load operation.