Iron Loss Reduction Research Articles

Rotor-Shape Optimization of Interior-Permanent-Magnet Motors to Reduce Harmonic Iron Losses

In this paper, we develop novel rotor designs of interior-permanent-magnet motors in order to reduce harmonic iron losses at high rotational speeds under field-weakening control. First, an optimization method, combined with an adaptive finite-element method, is applied to automatically determine the shapes of the magnets and rotor core. The optimized motor is manufactured to confirm the validity of the calculation. It is clarified that the iron loss of the optimized motor is reduced to nearly half of that of the conventional motor, without a significant decrease in maximum torque. Next, the contribution of each part of the rotor to the iron-loss reduction is analyzed by the experimental design method. Finally, several designs of the rotors are proposed from the viewpoints of manufacturing cost and performance.

Effect of Tension Coating on Iron Loss at Frequencies Below 1 kHz in Thin-Gauged 3% Si-Fe Sheets

Effect of tension coating on iron loss has been investigated as a function of excitation induction and frequency in thin-gauged 3% silicon steel sheets and iron loss after tension coating has been evaluated by loss separation method. In order to additionally reduce iron loss, tension coating without forsterite base coating was applied on surfaces of the thin grain-oriented sheets. Reduction in total loss due to the tension coating results from combination of hysteresis loss and anomalous loss, but the latter plays a major role in the loss reduction. The coated sheets show a maximum iron loss reduction of 18% at an excitation induction of 1.0 T and an excitation frequency of 60 Hz.

Development of interior permanent magnet motors reducing harmonic iron losses under field weakening control

AbstractIn this paper, we present the development of interior magnet motors reducing iron loss at high rotational speed under the flux weakening control. The rotor core and magnet shapes are determined by the automatic numerical calculation using combination of the optimization method and the adaptive finite element method. The optimized motor is manufactured to prove the effectiveness by the measurement of the iron loss. Both results of the calculation and the measurement indicate that the iron loss of the proposed motor at the high rotational speed under the flux weakening control is reduced by half compared with the initial rotor shape while the torque is nearly constant. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 59–66, 2009; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20827

Characterization and optimization of a permanent magnet synchronous machine

PurposeThe first purpose of this paper is to identify – by an inverse problem – the unknown material characteristics in a permanent magnet synchronous machine in order to obtain a numerical model that is a realistic representation of the machine. The second purpose is to optimize the machine geometrically – using the accurate numerical model – for a maximal torque to losses ratio. Using the optimized geometry, a new machine can be manufactured that is more efficient than the original.Design/methodology/approachA 2D finite element model of the machine is built, using a nonlinear material characteristic that contains three parameters. The parameters are identified by an inverse problem, starting from torque measurements. The validation is based on local BH‐measurements on the stator iron.FindingsGeometrical parameters of the motor are optimized at small load (low‐stator currents) and at full load (high‐stator currents). If the optimization is carried out for a small load, the stator teeth are chosen wider in order to reduce iron loss. An optimization at full load results in a larger copper section so that the copper loss is reduced.Research limitations/implicationsThe identification of the material parameters is influenced by the tolerance on the air gap – shown by a sensitivity analysis in the paper – and by 3D effects, which are not taken into account in the 2D model.Practical implicationsThe identification of the material parameters guarantees that the numerical model describes the real material properties in the machine, which may be different from the properties given by the manufacturer because of mechanical stress and material degradation.Originality/valueThe optimization is more accurate because the material properties, used in the numerical model, are determined by the solution of an inverse problem that uses measurements on the machine.

Consideration of Reduction in Eddy Current Loss in EIE-Core Variable Inductors

EIE-core variable inductors have useful features in that they are easy to scale up because they are made from a laminated silicon steel sheet, and their output current is almost sinusoidal without an air gap or a low pass filter. Hence, practical applications of EIE-core variable inductors as voltage regulators in electric power systems are expected. A highly accurate numerical calculation based on reluctance network analysis (RNA) was introduced in previous papers. Various characteristics including eddy current loss on the laminated silicon steel can be estimated using RNA. This paper proposes a method of reducing eddy current loss in variable inductors. The cutting plane of the EIE-core due to the reduced eddy current loss is determined based on the flux distribution calculated by RNA. An over 10% reduction in iron loss is demonstrated to be possible based on the proposed method.

The Improvement of Permeability and Strength in Soft Magnetic Composites Motor Core Using Spark Plasma Sintering Process

The practical uses of soft magnetic composite(SMC) for an electrical motor is presented in this paper. SMC allows obtaining improved stator and core shapes as well as totally new design concepts such as claw pole motor. However, a major disadvantage of soft magnetic composites was their weak strength. In this study, spark plasma sintering (SPS) was utilized to improve the strength of SMC. Advantages of the SPS process over other conventional sintering process are the faster heating and cooling rates ensured and higher pressure applied during the sintering procedure. This allows obtaining high strength products in short periods of time to meet with industrial application without insulation destruction. This paper introduces the development of high strength soft magnetic composite motor core and examples of practical application for industries. The result showed that the SPS process increased the fracture strength, about 1.3 to 1.7 times, of SMC compare to the conventional compaction. Also we derive method to reduce the iron loss in the SPS sintering process using control forming temperature. As the forming temperature decreased from 500°C to 300°C, reduction of iron-loss was obtained from 192W/kg to 21W/kg by using SPS sintering process. Moreover, with increased the SPS sintering process pressure value from 250MPa to 800MPa which is the conventional compaction condition and decreased forming temperature to 200°C, iron-loss was measured. The results showed that iron-loss was obtained 11.42W/kg and it was similar value of conventional compaction results.

無方向性電磁鋼板における究極鉄損の追求

This paper discusses the possibility of iron loss reduction in non-oriented electrical steel (NO) sheets with a composition corresponding to JIS grade 35A210, and estimates the optimum iron loss from experimental data. The hysteresis loss of processed pure NO steel was decreased by 0.27 W/kg from the present 35A210 standard. The 0.35-mm-thick NO sheets with random {100} textures and the optimum crystalline sizes of polycrystals and withoutprecipitation may decrease iron losses from 2.0 W/kg to 1.0 W/kg, because random {100} textures may reduce theeffects of steel surfaces on iron losses and make coercive forces low, and optimum crystalline sizes minimize total iron losses. If pure NO sheets with random {100} textures are used in motors, the iron loss of a motor may become low, notonly because those of the core materials are low, but also because the motor core characteristics improve as a result of uniform flux distributions due to the low coercive force and lower internal stress caused by magnetostrictions. The decrease in the hysteresis loss was about 20%, relative to the present 35A250 standard, in a 12-pole 9-slot motorwhere a core made of pure NO was excited by a NdFeB bonded permanent magnet, although the decrease in thehysteresis loss of the core material was only about 18%.

弱め界磁制御時の高調波鉄損を低減したIPMモータの開発

In this paper, we present the development of interior magnet motors reducing iron loss at high rotational speed under the flux weakening control. The rotor core and magnet shapes are determined by the automatic numerical calculation using combination of the optimization method and the adaptive finite element method. The optimized motor is manufactured to prove the effectiveness by the measurement of the iron loss. Both results of the calculation and the measurement indicate that the iron loss of the proposed motor at the high rotational speed under the flux weakening control is reduced by half compared with the initial rotor shape while the torque is nearly constant. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 59–66, 2009; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20827

磁化特性が巻鉄心型三相変圧器の鉄損特性に与える影響

This paper describes the influences of magnetization characteristics of the materials on the iron loss of wound-core type three-phase transformer. In the analysis, magnetization characteristics are approximated by a Fourier-series, and it is assumed that the eddy current factor is proportional to the time-varying magnetic flux. Moreover harmonic balance method where the zero-phase-sequence and third harmonic components of flux density are taken into consider is used. From the results of numerical analysis, it is shown that iron loss decreases as the ratio of eddy currents loss to iron loss of the material becomes minor. The importance of non-linearity of magnetization characteristics of the materials to reduce iron loss of wound-core type three-phase transformer is also shown. The analytical results agree roughly with the experimental result.

Iron Loss Reduction in an Interior PM Automotive Alternator

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper examines the iron loss characteristics of a high-flux interior permanent-magnet machine. The machine was designed as a concept demonstrator for a 6-kW automotive alternator and has a wide field-weakening range. Initial experimental results revealed a high iron loss during field-weakening operation. Finite-element analysis was used to investigate the cause of the high iron losses and to predict their magnitude as a function of speed. The effects of changes in the machine design were examined in order to reduce iron losses and hence improve the machine performance. </para>

Reducing Iron Loss by Decreasing Stress in Stator Core of Permanent Magnet Synchronous Motor

It is necessary to develop high efficiency motor, however, it comes a limit to increase efficiency because many motors already have very high efficiency. It is reported that iron loss of motor increase by shrink fit. Therefore, new motor shape is developed from a viewpoint of decreasing stator core stress caused by shrink fit. The relationship with iron loss and stator core stress is examined by the analysis, and the effect of new stator core is verified.

Recovering and recycling scrap from dumps containing steelmaking slags

The company Mittal Stil Temirtau has accumulated more than 13 million tons of steelmaking slag, and it annually adds another 600,000 tons of slag to this amount from ongoing production operations. Here, some of the iron from the production process is lost in the form of metallic iron and oxides. The total amount of iron lost is estimated to be 15%. Studies have established that discarded steelmaking slags contain up to 8% magnetic products. A slag-processing unit began operation at the dump in 2003 to recover scrap from the slag. The unit has a productivity of 120 tons of bank slag per hour and can process slag with an initial coarseness of up to 700 mm. Extracting iron-bearing products from steelmaking slags and returning them to the production cycle has reduced iron losses by 30% for the metallurgical conversion as a whole.

Transformers of reduced losses and evaluation of their repair

The purpose of this work is to determine the optimum reduction of iron and copper losses in distribution transformers. Design and life-cost calculations for transformers 20 kV/400 V of a nominal power 50–1000 kVA were performed, for estimating the final transformer price for different amounts of loss reduction, in order to find out the minimum annual operational cost of these transformers. For estimating the annual cost, the final transformer price and the power and energy cost due to the transformer losses have been used. In this way, the optimal losses (iron + copper) have been found out for the minimum annual cost. The impact of a damaged tranformer's age on the economic decision for its repair has been investigated as well.

Effects of laser irradiation on iron loss reduction for Fe–3%Si grain-oriented silicon steel

The effects of laser irradiation on iron loss reduction for Fe–3%Si grain-oriented silicon steel sheet were investigated. The local tensile residual stress states near the laser irradiated cavity lines were observed by using the new X-ray stress measurement method for a single crystal. Although the higher laser power induced the larger tensile residual stresses, the minimum iron loss was obtained at the medium tensile residual stress conditions of about 100–200 MPa. The increase of Vickers hardness was observed with increasing laser power, which was the mark of the plastic deformations induced by the laser irradiation. The tensile residual stress reduces eddy current loss and the plastic deformation increases hysteresis loss of the material. The total iron loss is determined by the balance of these two effects of laser irradiation.

Iron status and haematological changes in adolescent female inpatients with anorexia nervosa.

(i) To investigate the incidence of iron deficiency (both latent iron deficiency and iron deficiency anaemia) in post menarchal female adolescent patients hospitalized with anorexia nervosa. (ii) To observe changes in iron status during refeeding. During the study period all post menarchal female patients admitted to the adolescent unit with anorexia nervosa were invited to participate. Ferritin, serum iron, transferrin and transferrin saturation were measured on admission and discharge. Haemoglobin, haematocrit, weight, and body mass index were monitored weekly. All 12 eligible patients participated in the study. Four patients had elevated ferritin levels on admission. Ten of the 12 showed a statistically significant fall in serum ferritin at time of discharge compared with admission (P = 0.004). One of 12 patients had a low serum iron at presentation. All 12 had normal serum iron levels at discharge. Nine of the 12 subjects had a higher serum iron at discharge which was statistically significant (P = 0.046). There was no significant change in haemoglobin levels when comparing admission and discharge levels. Nine of the 12 patients however, transiently developed anaemia, at some stage during treatment. Iron deficiency is uncommon at both presentation and after nutritional rehabilitation in post menarchal adolescent females with anorexia nervosa. This is most likely due to increased iron storage secondary to the contraction of the circulating blood volume and reduced iron losses from (secondary) amenorrhoea. The fall in ferritin observed during treatment is due to haemopoiesis necessary to fill the increased blood volume associated with weight gain. This also results in normalization of the haemoglobin and haematocrit.

Experiences and Challenges in Industrialized Countries: Control of Iron Deficiency in Industrialized Countries

This paper provides a synopsis of the experience in combating iron deficiency in industrialized countries and identifies the reasons for the considerable success and future challenges. Significant progress has been made over the last century in reducing and even eliminating iron deficiency in many industrialized countries. Current estimates are that the prevalence of iron deficiency has declined to <20% in many of these countries, even among women and young children, compared with 30 to 70% in many developing countries. The reasons for this success cannot be attributed solely to a single approach but rather to a range of factors that have occurred over time as a result of both economic development and the implementation of specific policies. Several factors have contributed to improving both iron intakes and reducing iron losses; these include fortification, supplementation, dietary diversification and public health measures. For example, the decline in anemia in infants can be attributed to the introduction of iron-fortified formula and complementary foods in the 1960s to 1970s. Similarly, the enrichment and fortification of cereals with iron that began during World War II in North America and Europe is a result of effective public-private partnerships. Despite these successes, iron deficiency remains a public health concern in industrialized countries for selected subgroups such as women of reproductive age with excess menstrual losses and pregnant women who cannot meet increased requirements from the diet alone. Constant vigilance and innovative approaches for screening and combating this problem are thus still required even in developed countries.

A novel iron loss reduction technique for distribution transformers based on a combined genetic algorithm - neural network approach

The paper presents an effective method to reduce the iron losses of wound core distribution transformers based on a combined neural network/genetic algorithm approach. The originality of the work presented is that it tackles the iron loss reduction problem during the transformer production phase, while previous works concentrated on the design phase. More specifically, neural networks effectively use measurements taken at the first stages of core construction in order to predict the iron losses of the assembled transformers, while genetic algorithms are used to improve the grouping process of the individual cores by reducing iron losses of assembled transformers. The proposed method has been tested on a transformer manufacturing industry. The results demonstrate the feasibility and practicality of this approach. Significant reduction of transformer iron losses is observed in comparison to the current practice leading to important economic savings for the transformer manufacturer.

Improvement of T-joint part constructions in three-phase transformer cores by using direct loss analysis with E&amp;S model

This paper presents the effects of the joint method in the T-joint of three-phase transformer cores on iron losses. The effects of joints on the decrease of core loss have been analyzed by using FEM with E&S model, considering the hysteresis of vector magnetic properties. As a result, we can improve the T-joint part constructions to reduce iron losses in the three-phase transformer cores.

電磁鋼板表面の溝形成による磁区の細分化と鉄損の改善

電磁鋼板表面の溝形成による磁区の細分化と鉄損の改善

AI helps reduce transformer iron losses

Methods for iron loss reduction during manufacturing of wound-core distribution transformers are presented. More specifically, measurements taken at the first stages of core construction are effectively used, in order to minimize iron losses of transformer (final product). To optimally exploit the measurements (feedback), artificial intelligence methods are applied. It is shown that intelligent systems are able to learn and interpret several variations of the same conditions, thus helping in predicting iron losses with increased accuracy.