Loss Calculation Method Research Articles

Magnetic Field Analysis for Dimensional Resonance in Mn–Zn Ferrite Toroidal Core and Comparison With Permeability Measurement

This paper studies the calculation method of core loss and magnetic state in Mn-Zn ferrites under an arbitrary waveform excitation. The effective dielectric constant, which is caused by a thin high-resistive layer at the grain boundary, is treated as a modification of Ohm's law by using an equivalent circuit. This procedure enables us to calculate both the dimensional resonance and eddy-current loss. To confirm the accuracy of the proposed model, the size dependence of the complex permeability and core loss of the toroidal core is analyzed. These results show a good agreement with the experimental measurement in the megahertz region. By using the same model, the core loss mechanism excited by a triangular-wave current is analyzed. In the low-frequency region, the core loss is suppressed by the reduction of a steep change in magnetic flux. However, the core loss near the resonant frequency is increased at the turning point of the current wave, where the time derivative of the current changes discontinuously and a higher harmonic component is induced.

Temperature Field Analysis of High Efficiency Linear Pumping Unit

The generation of heat source of high efficiency linear pumping unit was analyzed. The calculation method of motor loss and heat dissipation coefficient was given. The finite element analysis software was used to simulate and analyze the temperature field of the linear pumping unit in the phase of constant motion and the starting and reversing phase. According to the analysis, it was concluded that the reasonable optimization of linear motor cooling structure can ensure the good temperature characteristics.

Determination of Specific Losses in Stator Core of Electromechanical Energy Converter

The purpose of this paper is the experimental research of the magnetic losses in electrical steels, soft magnetic alloys and amorphous alloys in the wide range of the magnetization reversal frequency and magnetic induction. The comparison between different analytical calculation methods of the stator-core specific losses is presented. The article shows that the known methods with the sufficient accuracy allows the stator-core-specific-loss calculation at frequencies below 400 Hz. However, the discrepancy with the calculations of losses by the different methods at the higher frequencies (above 400 Hz) can reach 2 times. The experimental research at high frequencies showed the 2-3-time discrepancy between the calculated and experimental data.

On the treatment of uncertainty in seismic vulnerability and portfolio risk assessment

SummaryIn a related study developed by the authors, building fragility is represented by intensity‐specific distributions of damage exceedance probability of various damage states. The contribution of the latter has been demonstrated in the context of loss estimation of building portfolios, where it is shown that the proposed concept of conditional fragility functions provides the link between seismic intensity and the uncertainty in damage exceedance probabilities. In the present study, this methodology is extended to the definition of building vulnerability, whereby vulnerability functions are characterized by hazard‐consistent distributions of damage ratio per level of primary seismic intensity parameter—Sa(T1). The latter is further included in a loss assessment framework, in which the impact of variability and spatial correlation of damage ratio in the probabilistic evaluation of seismic loss is accounted for, using test‐bed portfolios of 2, 5, and 8‐story precode reinforced concrete buildings located in the district of Lisbon, Portugal. This methodology is evaluated in comparison with current state‐of‐the‐art methods of vulnerability and loss calculation, highlighting the discrepancies that can arise in loss estimates when the variability and spatial distributions of damage ratio, influenced by ground motion properties other than the considered primary intensity measure, are not taken into account.

Experimental study on surface topography and fracture strength of worn saw wire in multi-wire sawing

In multi-wire sawing, reducing the wire wear loss and increasing wire consumption are the common means to avoid the risk of saw wire breakage because the worn saw wire experiences a complex process with strength degradation and surface damage. So, it is urgent and necessary to give a reliable wire wear loss in theory. This paper focused on the surface topography and fracture strength of worn wire with different wire wear loss. Furthermore, the saw wire maximum safety wear loss model was presented based on the experimental results. By observing the surface topography of the worn saw wire, the dented traces were distributed on the whole surface and a few grooves with large depth were shown in the local zone. The cross-sections of the worn saw wires with different wear loss were circular. In addition, its fracture strength of the wore saw wires was not reduced with the increasing of the saw wire wear loss. On the contrary, the fracture strength of the wire with large wear loss was improved by hardening in comparison with fresh saw wire. This phenomenon suggested that surface damages did not affect the fracture strength of saw wire under the experimental condition. Furthermore, fracture photograph of the fracture test samples was divided into the crack propagation zone and final fracture zone. By analyzing these fracture topography, almost all the crack propagation zones were circular and its diameter was about 48.27 μm. It is not correlated with the amount of wear loss. However, the shape became non-circular in some samples with large depth damage on the surface. By summarizing these results, the model and calculation method of the maximum safety wear loss of saw wire were established, which could provide the theoretical basis for the determining the maximum safety wear loss.

The Effects of Water Flow Rate on Copper Corrosion

This study investigates the effect of water flowrate on the copper alloy corrosion by using a hydrodynamic corrosion test in operating conditions of water flow rate range between 0.05 and 3.5 m/s, the temperature range between 20 and 45 °C. Dissolved oxygen concentration was in the range between 6.1 and 9.2 mg/l. The effects of water properties density, viscosity, and the tube geometric dimensions also considered. Corrosion rate determined by the weight loss calculation method and the tested samples microstructures characterized using FESEM. The results showed that the copper surface layer more affected by water flow at the beginning of turbulent flow condition, while at fully developed turbulent flow condition the surface covered with a fixed oxide layer. Therefore, corrosion found to be at higher rates during the initial stage of the turbulent flow condition, but it reduced at fully developed turbulent flow conditions at higher water velocity. These results indicate that the overall flow rate conditions, which include physical properties of the fluid, hydrodynamic parameters, and the geometric tube dimensions, have the dominant influence on corrosion rate.

A New Approach for Modeling of Hysteresis in 2-D Time-Transient Analysis of Eddy Current Using FEM

Eddy current is the origin of resistive loss in magnetic cores. In conventional method of eddy loss calculation, flux density is assumed to be distributed uniformly. However, the eddy-current forces the magnetic flux to flow through the skin of magnetic core, the effect that is called flux skin effect. For wave forms other than the sinusoidal form or for non-linear relationship between H and B, there is not analytical solution for the field equations. In such cases, magnetic field and the eddy-current equations must be solved by numerical methods such as finite-element method. Moreover, numerical modeling is helpful in estimating the eddy-current patterns that are used in non-destructive tests to detect the presence of any possible cracks. In order to achieve the flux distribution in the presence of the eddy current, the diffusion equation should be solved. This paper presents a new approach for finite-element analysis of 2-D diffusion equation. The solution is in time-domain, and the hysteresis behavior of ferromagnetic material is included in it. Analysis results show that skin effect has considerable influence on the eddy and hysteresis losses. Presented method has the capability of eddy-current analysis for any shape of cores, including hysteresis behavior.

Development of conductive parts power losses calculation method in case of interharmonics

Development of conductive parts power losses calculation method in case of interharmonics

Two methods of AC loss calculation in numerical modelling of superconducting coils

Numerical methods are widely utilised in the prediction of AC loss in superconducting coils. A commonly used approach is based on determination of the local dissipation calculated from the distributions of electrical field and current density throughout the winding, as well as its evolution over the AC cycle. This quantity reflects the heat release on a microscopic scale, and its integration throughout the coil winding over one AC cycle provides the value of loss per cycle in the coil. On the other hand, one can look at global quantities characterising the energy flow from a power supply to the coil: the electrical current supplied and the voltage on its terminals. Averaging, with respect to time, of the voltage times current product also gives the coil loss per cycle. Here we show that a comparison of results obtained with ‘local’ and ‘global’ methodologies can be useful in identifying the numerical errors caused by calculation techniques. However, this is possible only when the modelling method allows for determination of the essential physical quantities as independent variables. We illustrate this approach with an example utilising the A-φ and H-formulations for the AC loss evaluation in a ten-turn pancake coil wound from coated conductor tape.

Characterization of Iron Loss for Integral-Slot Interior Permanent Magnet Synchronous Machine During Flux Weakening

Iron loss resistance is widely used for rapid motor design and maximum efficiency control. However, the harmonic loss obviously increases during flux weakening, and even dominates in total iron loss, especially in deep flux weakening region. This paper presents an analytical calculation method of iron loss for an integral-slot interior permanent magnet synchronous machine (IPMSM) by iron loss resistance, considering harmonic effect during flux weakening. To predict the harmonic loss, both a harmonic loss voltage and a harmonic loss coefficient are employed into an iron loss resistance model, and the relation of harmonic loss to the harmonic voltage and coefficient are studied. The iron loss and efficiency of an integral-slot IPMSM are, respectively, obtained by the proposed model, the conventional model, the experiment, and finite-element analysis (FEA). The proposed model is validated by the comparison with FEA and experimental results.

Calculation of Iron Loss of Medium-sized High Voltage Motor which Have Axial Ventilation Holes in Rotor

When optimizing the ventilation and cooling system of medium-sized high power density asynchronous motor, it is found that the temperature rise of the motor can be greatly reduced after punching the axial ventilation holes in the rotor yoke, but the traditional method based on the magnetic circuit method cannot accurately calculate the motor iron loss of this new structure. In this paper combined with the finite element field-circuit-motion coupled analysis method, taking YXKK355-4, 355kW and YKK400-4, 400kW medium-sized high voltage asynchronous motor for example, a two-dimensional geometric model and mathematical model of the motor are established, then the iron loss calculation method is improved. Using this method not only the iron loss value of the whole motor can be obtained, but also the specific distribution of iron loss in different areas of the motor can be known, and the correctness of the simulation results is proved by experiments.

Analysis of Power Loss and Improved Simulation Method of a High Frequency Dual-Buck Full-Bridge Inverter

A high frequency dual-buck full-bridge inverter for small power renewable energy application is proposed in this paper. A switching frequency of 400 kHz is achieved with the adoption of the SiC power device. A two-pole two-zero (2P2Z) compensator is employed in the outer voltage loop to generate the current reference for inner current loop. A 3P3Z compensator is adopted in the inner current loop to track the current reference. A systematic way for calculating the losses of high frequency inverter is presented, and the losses of the components are thoroughly analyzed. The turn-on and turn-off procedures of the inverter are discussed in detail. The losses caused by high frequency are calculated accurately, and the loss distribution is established as well. The procedure of the loss analysis gives a practical example for calculating the loss of similar type inverters. Moreover, deviation between pulse width modulation (PWM) control signal and switching response in high frequency switching is thoroughly analyzed. The influence of deviation is verified by designed experiment. Hence, a compensation method is proposed in order to minimize the influence. The compensation effect is validated by experiment and simulation. Finally, a 1-kW prototype is built to verify the feasibility of the theoretical analyses. The grid-connected maximum output power experiment is completed at 1 kW with the efficiency of 96.1% and the total harmonic distortion (THD) of 1.8%. The comparison experiments of power loss between Si and SiC power devices are carried out. The experiment results confirm the loss calculation method to be valid.

鉄損の直流磁界バイアス特性を考慮した降圧チョッパ回路用インダクタの低損失設計

In order to increase the power density of power converters, reduction of both the loss and the volume of the inductor is essential. However, it is difficult to calculate the iron loss of the inductor with the Steimetz equation or the improved generalized Steinmetz equation (iGSE) because those calculation methods do not consider the loss dependency of pre-magnetization. Hence, we have to repeat the re-design process in order to reduce the inductor loss or the inductor volume. In this paper, the authors propose an accurate loss calculation method for the inductor used in the buck-chopper circuit that is based on the iron loss characteristic considering pre-magnetization. In addition, the overall loss of the inductor is compared among three typical magnetic materials, such as iron powder, sendust, and ferrite, which have different iron loss characteristics for pre-magnetization. As a result, the sendust-based inductor achieves both the same loss reduction and a smaller volume compared with the ferrite-based inductor. From these studies, it is concluded that the proposed loss calculation method, which takes into account the loss dependency of pre-magnetization, is useful for optimum design of the inductors.

Efficiency limit factor analysis for the Francis-99 hydraulic turbine

The energy loss in hydraulic turbine is the most direct factor that affects the efficiency of the hydraulic turbine. Based on the analysis theory of inner energy loss of hydraulic turbine, combining the measurement data of the Francis-99, this paper calculates characteristic parameters of inner energy loss of the hydraulic turbine, and establishes the calculation model of the hydraulic turbine power. Taken the start-up test conditions given by Francis-99 as case, characteristics of the inner energy of the hydraulic turbine in transient and transformation law are researched. Further, analyzing mechanical friction in hydraulic turbine, we think that main ingredients of mechanical friction loss is the rotation friction loss between rotating runner and water body, and defined as the inner mechanical friction loss. The calculation method of the inner mechanical friction loss is given roughly. Our purpose is that explore and research the method and way increasing transformation efficiency of water flow by means of analysis energy losses in hydraulic turbine.

An Improved Method of the Energy Loss Calculation Considering the Volatility of Wind Power Generation

The energy loss of the power grid is one of the key factors affecting the economic operation of power systems. How to calculate the electric energy consumption accurately will have a great influence on the planning, operation and management of the power grid. Currently there is a mountain of theoretical methods to calculate the line loss of the power system. However, these methods have some limitation, such as less considering the volatility of wind power resources. This paper presents an improved method to calculate the energy loss of wind power generation, considering the fluctuations of wind power generation. First, data are collected to obtain the curve of the typical daily expected output of wind farms for one month. Second, the curve of the typical daily expected output are corrected by the average electricity and the shape factor to obtain the curve of the typical daily equivalent output of wind farms for one month. Finally, the power flow is calculated by using typical daily equivalent output curve to describe the energy loss for one month. The results in the 110 kV main network show that the method is feasible.

Loss calculation method for hybrid excited machines

Loss calculation method for hybrid excited machines

Calculation method and application of loss of life caused by dam break in China

Dam failure constitutes a grave threat to human life. However, there is still a lack of systematic and comprehensive research on the loss of life (L) caused by dam break in China. From the perspective of protecting human life, a new calculation method for L occurred in dam break floods is put forward. Fourteen dam failure cases in China are selected as the basic data by three-dimensional stratified sampling, balancing spatial, vertical elevation and temporal representations, as well as considering various conditions of the dam collapse. The method includes three progressive steps: Firstly, some impact factors of loss of life (IFL) are selected by literature survey, i.e., severity of dam break flood (S F), population at risk (P R), understanding of dam break (U B), warning time (T W) and evacuation condition (E C). And the other IFL of weather during dam break (W B), dam break mode (M B), water storage (S W), building vulnerability (V B), dam break time (T B) and average distance from affected area to dam (D D) are also taken into account to get a more comprehensive consideration. According to disaster system and disaster risk, these eleven IFL are divided into four categories. Through the improved entropy method, eight key IFL are further selected out of the eleven. Secondly, four L modules are built based on four categories, which are L-causing factor module (M 1), L-prone environment module (M 2), affected body module (M 3) and rescue condition module (M 4). Eventually, by using two methods of multivariate nonlinear regression and leave-one-out cross-validation in combination with coupled four modules, the calculation method for L is established. Compared with the results of Graham method and D&M method, the result of the proposed one is much closer to the actual value and performs better in fitting effect and regional applicability. In the application, L calculation and consequence assessment are carried out in the example of Hengjiang reservoir that has already broken down. At the same time, L calculation and risk prediction are used in the analysis of Yunshan reservoir, which is under planning. The proposed method can not only be applied to estimate L and its rate (f L ) under various types of dam break conditions in China, but also provide a reliable consequence assessment and prediction approach to reduce the risk of L.

Energy Model of Pulse Continuously Variable Transmission

The low efficiency restricts the development of pulse continuously variable transmission (P-CVT) mainly, so it is an urgent task to reveal the physical essence of P-CVT, find out the main factor of energy loss, optimize the structure and improve the efficiency. In this paper for this problem, the energy model is established, proposing the calculation method of the energy loss in kinematic pair, the energy loss caused by the resistance of lubrication and the energy loss caused by the damping of the materials of transmission machine. And on this basis, the energy loss will be analyzed specifically by taking the Y2 P-CVT for example, pointing out the corresponding measures which can improve the efficiency. Finally, the physical essence of P-CVT is revealed. Therefore, this paper can provide theory for the efficiency analysis and optimal design of P-CVT.

Study of 2G HTS Superconducting Coils Using Line Front Track Approximation

This paper demonstrates an efficient method to calculate the ac losses in multipancake coils. We use the front track line to analyze stacked pancakes by assuming that the current fronts are straight lines and using the critical state model. The current distribution is solved by minimization of total magnetic energy. The calculated ac loss results are compared with the well-accepted H-formula in COMSOL. We further apply this model to the design of a SMES with 2 kJ, which is under construction. The object of the design is to maximize the stored energy and decrease the ac loss. We discuss the detailed geometry parameters and operation temperature with the validated numerical model. Our model provides a fast calculation method of ac loss in stacked (Re)BCO pancakes and is useful to HTS applications in high field magnets, energy storage devices, and electric machines.

Study of the Stray Losses Calculation in Structural Parts for HVDC Converter Transformers Based on the TEAM Problem 21 Family

The stray losses calculation method proposed by the IEC 61378-2 standard is analyzed in this study. The fundamental stray losses in different currents and the harmonic stray losses of the TEAM Problem 21 Family members are analyzed to verify the IEC method. It is shown that stray losses are approximately proportional to the square of the current, but do not follow the frequency to the power of 0.8. The IEC method typically produces large errors. A corrected calculation method is thus proposed in this study, in which the magnetic-field distribution is considered. The corrected method is verified in comparison with experimental results and the IEC method.