Transformer Manufacturers Research Articles

Isolation of aroclor1254 degrading bacteria in contaminated soil by transformer oil

ABSTRACT- Aerobic biodegradation is an environmental-friendly biological method that allows micro organisms to remove persistent organic pollutants. Aroclor1254 is a mixed compound containing polychlorinated biphenyls (PCBs) along with persistent organic materials. There is no estimate of Aroclor1254 usage and its release into the environment in Iran. A transformer manufacturing plant in Shiraz (located in southwest of Iran) uses transformer oils containing Aroclor1254. Soil samples contaminated by transformer oil were taken from the manufacturing plant’s site and were tested for the presence of certain bacteria, level of degradation and pH. In all samples, 13 bacterial strains were isolated on C-media, and their growth was measured using a spectrophotometer. Of the isolated strains, eight could degrade Aroclor1254. Of these eight strains, three showed weak growth (OD between 0.1 to 0.195), three showed low growth (OD between 0.2 to 0.3) and two showed good growth (OD between 0.3 to 0.5). Some of the strains grew well during the first week, but their growth decreased and eventually stopped in the second week. For all the growth media on which the bacteria from the soil was separated and cultured, pH decreased as the bacterial growth increased. For some media, in which bacterial growth had stopped, pH increased after 14 or 21 days but it was always below 7.0. This indicated that environmental pH or increasing carbon dioxide levels were not suitable for the growth of these strains. However, this trend was not observed in bacteria belonging to Pseudomonas, Curtobacterium and Burkholderia. These bacteria could grow and degrade Aroclor1254 even at pH of 4.5. In fact, their degradation efficiency increased at a constant pH of about 5.5.

Impulse voltage distribution and frequency response of intershield windings

Impulse voltage distributions in continuous disk windings are nonlinear, due to the small series capacitance of the winding. Consequently, transformer manufacturers often design large power transformers with interleaved windings to increase series capacitance, but in doing so reduce the value of the initial impulse voltage distribution coefficient α given by α = √(Cg/Cs), (1) where Cg is the shunt capacitance and Cs is the series capacitance of the winding. Sometimes fully interleaved windings are employed because they are more reliable, ensuring that the transformer will operate properly under lightning strike. However, fully interleaved windings require longer assembly times, and manual welding is necessary. Manufacturers have therefore been using series combinations of continuous and interleaved windings, known as multiple-α type windings [1]. However, this approach also has disadvantages, e.g., the design and analysis of performance under normal and abnormal transient conditions are complicated, and the impedances of continuous disks differ from those of interleaved disks [2], causing reflection of surge traveling waves at connection points. Transformer designers may therefore have to adjust inter-disk distances and repeat transient simulation studies several times, to find an optimum arrangement.

Using 3D printers as weapons

Additive manufacturing, also known as 3D printing, is a transformative manufacturing technology that will play a significant role in the critical manufacturing sector. Industrial-grade 3D printers are increasingly used to produce functional parts for important systems. However, due to their reliance on computerization, 3D printers are susceptible to a broad range of attacks. More importantly, compromising a 3D printer is not a goal, but rather a staging point for launching subsequent attacks with the printer. For example, an adversary can compromise a 3D printer in order to manipulate the mechanical properties of manufactured parts. If the manufactured parts are used in jet engines or in other safety-critical systems, they could endanger human life, disrupt critical infrastructure assets and produce significant economic and societal impacts.This paper analyzes the ability of an adversary to “weaponize” compromised additive manufacturing equipment in order to cause kinetic, nuclear/biological/chemical or cyber damage. In particular, the paper presents categories (taxonomies) of the elements in an additive manufacturing workflow that can be compromised by successful attacks, the manipulations that the compromised elements can exercise and the weapon-like effects resulting from these manipulations. The relationships between these taxonomies are discussed. Finally, the weaponization capabilities of 3D printers are characterized.

Flow time and product cost estimation by using an artificial neural network (ANN): A case study for transformer orders

ABSTRACTIn electromechanical industrial corporations, determining the production cost of the orders according to the technical specifications demanded by the customer has great importance in giving an accurate price offer. Labor cost is one of the important and most variable cost components that must be estimated in order to give an accurate price offer. In this study, a feed-forward back-propagation artificial neural network (FF-BPN) is used to predict the flow times of power transformer orders of a transformer producer according to the technical specifications given by the customer. The results of this study show that the prediction capability of an artificial neural network is very good for this type of problem and results in better cost estimation than current company practice. A case study is carried out for a manufacturer of electrical transformers in Turkey.

Rotational Core Loss of Silicon Steel Laminations Based on Three-Dimensional Magnetic Properties Measurement

Magnetic properties of silicon steel laminations are important features in power transformer and electrical machine design and manufacture. Conventional testing methods such as Epstein Frame and Single Sheet Tester may only consider one direction or one sheet, which may deviate from the real application, particularly in core loss calculation. A 3-D magnetic properties' testing method is proposed in this paper. By using the designed special surface B-H sensing coils, the dynamic magnetic hysteresis properties of a laminated non-grain-oriented silicon steel sample are accurately measured. The relationship between B and H in alternating, 2-D rotational, and 3-D spherical rotational excitations, from 50 to 200 Hz, is studied and analyzed. In order to control the B waveform better, the harmonics of B x and B y signals are analyzed at 50 Hz. The alternating core losses in the rolling, transverse, and laminated directions and the rotational core losses in the xoy plane of this sample at 50, 100, and 200 Hz are calculated and analyzed. Moreover, the core losses in the three directions are well predicted by means of total core loss separation theory.

A coupled internal–external flow and conjugate heat transfer simulations and experiments on radiators of a transformer

Experimental and numerical studies are reported on radiator–fan assembly, for ONAN (Oil Natural and Air Natural) and ONAF (Oil Natural and Air Forced) cooling configurations. In-house radiator test facility is developed for the experiments, and commercial software is used for the simulations. Simulations considered oil inside and air outside the radiator, and the conjugate (conduction–convection–radiation) heat transfer. Present study is done on a group of 5 radiators (of 2.5m height), each with 27 fins, and 2 fans (of 1m diameter). Good agreement, between the numerical and the experimental results, are reported for heat dissipation from the radiators. Numerical study is done to study the effect of the vertical as compared to a horizontal air flow on the thermal performance. Significant effect of the flow direction is reported on the oil flow and temperature distribution inside the radiators, with 6.1% more heat dissipation by the horizontal as compared to vertical air flow. An average oil temperature distribution inside the radiators along the height follows an exponential decay distribution, in contrast to the traditional linear profile assumption for all configurations of transformer cooling. The study is useful for transformer designers and manufacturers, leading to an improvement in the thermal design.

Effects of oil leakage on thermal hydraulic characteristics and performance of a disc-type transformer winding

Conjugate heat transfer problem of a disc winding in a power transformer is studied using commercial CFD software. The study is done for oil flow, temperature distribution, hot spot location and temperature of the winding, for three different cases: first, no oil leakage past the top washer; second, partial leakage due to a 2 mm gap between the top oil guiding washer and cylindrical pressboard; third, full leakage, i.e., no oil guiding washer. The effect of leakage is studied for both uniform and non-uniform heat loss distributions in the winding. The leakage is found to lead to an onset of a reversal in flow direction: in the horizontal channels of the last pass of the winding. Under the effect of leakage, the variation in thermal performance of the winding is substantial for uniform and negligible for more practically encountered non-uniform heat loss distribution. However, for non-uniform heat loss distribution, the leakage leads to two local hotpots as compared to one for the non-leakage case. The partial as compared to complete leakage is found to give almost same thermal performance. This study will be useful – for transformer manufacturers – to realize the importance of leakage free washer design of a disc-type transformer winding.

How to implement strategy more effectively

To execute a strategy more effectively, this study develops a model modifying the resource-based 'McKinsey's 7S' through the industrial organisation point of view. To do so, the 'comprehensive strategic management model' and the article on 'how the balanced scorecard complements the McKinsey's 7S model' are employed. The model was tested on a transformer manufacturer, and findings prove that neither viewpoint is independently effective. Indeed, combining both views, this study employs the strategy formulation and management control system to contribute to resolving the most difficult stage of strategic management (implementation).

A Review on Properties, Opportunities, and Challenges of Transformer Oil-Based Nanofluids

The mineral oil or synthetic oil in conjunction with paper is mainly being applied as dielectric medium in many of the high voltage apparatus. However, the advent of high voltage levels such high voltage alternating current (HVAC) and high voltage direct current (HVDC) has prompted researchers to direct their focus onto an insulation system which can bear the rising high voltage levels. The modern insulating liquid material development is guided by various factors such as high electrical insulation requirements and other safety and economic considerations. Therefore transformer manufacturer companies have to design transformers with these new specific requirements. The transformer oil-based nanofluids with improved dielectric and thermal properties have the potential to replace mineral oil base products in the market place. They are favorable because they function more superior than mineral oil and they contribute definite insulating and thermal gains. This paper reviews recent status of nanofluids use as transformer oils. The nanofluids used as transformer oils are presented and their advantages are described in comparison with mineral oil. The multiple experimental works carried out by different researchers are described, providing an overview of the current research conducted on nanofluids. In addition scope and challenges being confronted in this area of research are clearly presented.

NWL: From a Transformer Repair Shop to Specialty Component Manufacturer [Member and Industry Profile

What started as a small transformer repair shop in Trenton, New Jersey, in the 1930s is now a leading manufacturer and designer of transformers, inductors, capacitors, and power supplies for industrial and military applications with a specialization in switched-mode power supplies (SMPSs) for electrostatic precipitators (ESPs), electron-beam curing and melting, and other high-reliability systems. Today, there are four independently operating production groups under one roof, with each producing a family of specialized transformers and power supplies. Spread across a 185,000-formula><tex>${\rm ft}^{2}$</tex></formula> facility in Bordentown, New Jersey (Figure 1), NWL currently produces over 100 cutting-edge units per month for a global customer base that has spread beyond the U.S. shores to Europe, South America, and the Pacific Rim.

A hybrid genetic algorithm for the hybrid flow shop scheduling problem with nighttime work and simultaneous work constraints: A case study from the transformer industry

This paper addresses a hybrid flow shop scheduling problem with real-world constraints, and proposes a novel algorithm for its solution. We first discuss the distinguishing characteristics of nighttime and simultaneous work in the transformer manufacturing process. To solve the problem within a reasonable time, we propose a hybrid genetic algorithm. This algorithm combines the Nawaz–Enscore–Ham (NEH) heuristic, a local search algorithm, and a machine allocation rule with the aim of minimizing the total tardiness. Our experimental results show that the proposed algorithm outperforms the NEH algorithm, a simple genetic algorithm, and five existing dispatching rules in terms of average total tardiness performance and relative deviation index. The proposed algorithm is also shown to be competitive with respect to its efficiency and robustness.

Transformed

This article describes the shift in manufacturing of transformers in the United States and its benefits. In the wake of the September 11 attacks, the grid’s heavy reliance on imported equipment was seen as vulnerability. The RecX project focused on transportation and speedy installation of a modularized grid transformer rather than grid standardization. Home-based manufacturing of transformers can have major implications for the security and robustness of the grid. Building big transformers in the United States, closer by thousands of miles to installation sites, can simplify and speed up the development of transformers. Shorter distances can also reduce transport time. Large-scale loss of grid transformers is considered a high-impact, low-frequency event. The distant manufacturing sites and long delivery times that so worried government officials in the past have been seen in a new light. They represent an annual replacement market of several hundred massive machines, sufficient to support a major manufacturing expansion in North America.

Mejoramiento de procesos de manufactura utilizando Kanban

This paper presents the application of the Kanban methodology and analysis of the effect that this can generate in a manufacturing of distribution transformers. By applying the proposed methodology can be improved production scheduling, with the aim of reducing the amount of product in process is not used, so that inventory is reduced. To analyze the effect of applying the Kanban methodology in the company, the simulation technique was used, for which the current process and proposed to the rules of the Kanban methodology is modeled. From these results that yield modeling, it shows that there is an improvement in production lines where kanban methodology is used.

电力变压器的振动和噪声及消减措施研究

随着越来越多变电所建于居民区和商业区内，变压器噪声问题变得十分突出。变压器噪声水平的高低，已经成为了衡量变压器生产厂家设计和制造水平的重要指标。在负载电流工况下，变压器的振动和噪声主要是由绕组电磁力产生的。本文从噪声传播路径考虑，研究了振动和噪声的来源和传播途径，以及相应的消减措施，利用ANSYS Workbench和Virtual.Lab Acoustics软件联合仿真，建立了变压器实体模型，通过数值分析方式模拟变压器电磁作用产生的振动和噪声，初步验证了消减措施效果。变压器振动和噪声试验进一步验证了消减措施的有效性，同时证实了数值分析方法的可靠性。 As more and more substations are built in residential and commercial areas, transformer noise becomes very prominent. Transformer noise level has become the important indicator to measure design and manufacture level of transformer manufacturers. Under working condition of load current, the main source of transformer vibration and noise is winding electromagnetic force. Considering from noise propagation path, this paper studies the source of vibration and noise, route of transmission and the corresponding reduction measures. It takes advantage of ANSYS Workbench and Virtual Lab Acoustics software to simulation analysis and builds the solid model of transformer. On the basis of the solid model, it simulates transformer vibration and noise generated by electromagnetic interaction by means of numerical analysis method and preliminarily verifies the effect of the reduction measures. Then, the test of transformer vibration and noise further verifies the effectiveness of the reduction measures and meanwhile confirms the reliability of the numerical analysis method.

Optimum Circumscribing Circle Division Method for Getting Maximum Fill Factor in Transformer Core

As far as the optimum design of transformer is concerned, researchers generally concentrate on minimizing cost, no load and load losses etc. by choosing K-factor, Flux density, Current density etc. as design variables. But, the design of core has remained an unexplored area. Transformer manufacturing industry uses traditional technique to find out the core design dimensions. However, in that method, the fill factor for the desired number of steps is not maximized. The advantages of maximizing the fill factor includes reduced diameter and hence reduced copper material and associated cost and losses, increased efficiency, etc. In this paper, a new method, referred to as Optimum Circumscribing Circle Division Method (OCCDM), is suggested to maximize the fill factor for the desired number of steps in the transformer core.

Interfacing &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;${\rm k}$&lt;/tex&gt;&lt;/formula&gt;-Factor Based White-Box Transformer Models With Electromagnetic Transients Programs

White-box transformer models are used by transformer manufacturers during the dielectric design of windings. The models are often based on constant parameters (RLCG matrices) with the high-frequency losses accounted for by a scaling of the dc resistance ( k-Factor). We show an efficient procedure for interfacing such models with Electromagnetic Transients Program (EMTP)-type circuit simulators via state equations and a Norton equivalent. The approach makes no approximations except for the discretization in the time domain. Diagonalization is utilized for achieving high computational efficiency. Proprietary information about internal voltages is optionally hidden from the user. Internal surge arresters are handled by the EMTP circuit solver by declaring their connection points as external nodes. The model interface includes automated initialization from 50/60-Hz initial conditions. The proposed interfacing capability permits manufacturers to apply their models in complete network simulations, and to share their models with users.

NUMERICAL INVESTIGATION OF MECHANICAL AND THERMAL DYNAMIC PROPERTIES OF THE INDUSTRIAL TRANSFORMER

Industrial transformer is one of the most critical assets in the power and heavy industry. Failures of transformers can cause enormous losses. The poor joints of the electrical circuit on transformers can cause overheating and results in stress concentration on the structure which is the major cause of catastrophic failure. Few researches have been focused on the mechanical properties of industrial transformers under overheating thermal conditions. In this paper, both mechanical and thermal properties of industrial transformers are jointly investigated using finite element analysis (FEA). Dynamic response analysis is conducted on a modified transformer FEA model, and the computational results are compared with experimental results from literature to validate this simulation model. Based on the FEA model, thermal stress is calculated under different temperature conditions. These analysis results can provide insights to the understanding of the failure of transformers due to overheating, therefore are significant to assess winding fault, especially to the manufacturing and maintenance of large transformers.

A method for the determination of the presence of short-circuited coils in the windings of transformers

One of the most characteristic defects in the manufacture of transformers during mass production is the presence of short-circuited coils (SCCs) in windings. The advantages of a method for the control of this defect via measurements of the Q-factor in relation to industrially used analogous control methods based on measurements of inductivity or losses in a transformer is shown on the basis of a mathematical model and analytical studies. An experimental apparatus for the empirical testing of the main theoretical concepts is developed.

Analytical Calculation of the Electrical Energy Losses on Fixed-Mounted PV Plants

This paper presents analytical expressions for the annual energy losses on dc and ac cables, the annual energy losses on the step-up transformer, and the optimum transformer size for fixed-mounted photovoltaic (PV) plants of any size. These expressions are based on some unknown parameters, which can be easily estimated from data provided by the equipment (inverters or transformer) manufacturer and from available data in any meteorological database. The analytical expressions are meant to be used by the design engineers for comparing-from the energetic point of view-different cable cross sections and transformer sizes with various power loss classes or cooling medium, without having to perform multiple detailed simulations, as the current practice is. The validity of the derived expressions was tested against measurements taken in two existing 1003.52- and 491.4 kW <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> PV installations during the past 2 years. The proper use of the derived expressions during the design phase of a PV system is demonstrated through a detailed working example.

Experimental Study on Short-Circuit Withstand Capability of 110kV Power Transformer

Short-circuit withstand capability test of transformers is mechanical strength withstand test under strong current imposed on power transformers, which is a kind of assessment method of comprehensive technical capabilities and technological level of transformer manufacturing. This paper analyzes the theory basis of short-circuit withstand capability test and calculates the imposed short-circuit current value and provides experimental scheme which is verified by the testing. All is to verify the ability to withstand a short circuit of 110kV power transformer.