Tamás Orosz

Analysis of SAP Development tools and methods

Enterprise Resource Planning Systems enable their users to work in several functional areas, industry solutions. SAP, the leading ERP System in the World, delivers the newest standard information technology, architecture and methodology when introducing its new product. New features of the introduced product gradually replace the old techniques and approaches. Nevertheless, such informatics systems are more robust to get rid of older techniques immediately. There are still existing important solutions in the SAP systems using old Development tools and methods. There is a lack of learning methodology to bridge the gap of old, reliable and new technology. Present paper demonstrates how old techniques can still exist in the newest SAP architecture. This development example provides our students information about old but efficient Development Tools and Techniques.

Metaheuristic Optimization Preliminary Design Process of Core-Form Autotransformers

Because of the strong competition in the equipment market, the aim of the manufacturers is to reduce the product price as much as possible, fulfill the high-quality standards, and improve the reliability and efficiency of the transformers. The capitalization of the costs enables to handle the different economic and technological parameters together in the same cost function. Large power autotransformers are usually designed for specific economic and technical conditions specified by the customer. At the tender design stage, the most economical solution has to be found in a limited time, and a great number of feasible transformer designs have to be compared to find the optimal solution. Nowadays, the solution of this design process is mainly based on the experience of the transformer designer, but mathematical programming models can facilitate the process. It is well known that the design of shell-type power transformers can be optimized by geometric programming. The constructed models of geometric programming can be solved accurately with the interior-point-method-based solvers. According to the results, this kind of modeling is not applicable for the core-form transformers. However, with branch-and-bound search, the geometric programming method can also be used for these cases. This paper introduces a new algorithm, which can also handle the autotransformer designs with different positions of the regulating winding by applying a more general metaheuristic routine to perform the calculation of the short-circuit impedance.

Modeling the high frequency behavior of the Rogowski-coil passive L/r integrator current transducer with analytical and finite element method

The Rogowski current transducers are widely used because they have several advantages over iron-cored devices: no saturation at high current, higher operating frequency and less error in wider measurement range. The main components of these current transducers are the measuring coil and integrator. Latter can be passive or active. The main advantage of passive integrator is the wider bandwidth. The simplest is the L/r integration method, where the coil itself makes the operation of integration. In this case the knowledge of the resistance and the inductance of the coil not enough to make a proper equivalent circuit model, because the upper limit of the frequency characteristic depends on the distributed capacitance of the winding. The paper of Tamus (2002) has showed a new analytical model, which takes the distributed capacitance of the windings into consideration. The knowledge of distributed capacitances enables to calculate the upper frequency bandwidth limit and can help to determine the phase error decrease at normal frequencies. This analytical model is based on the classical lumped parameter winding model in the work of Karsai et al. (1987), which originally designed for large power transformers and assumes continuous voltage distribution along the windings. In this paper, the authors present a finite element method for calculation of distributed capacitances of winding, where the discrete behavior of the turns is taken into consideration to make a novelty for the estimation of the upper frequency limit, which cannot be determined correctly from the analytical calculation.

Design Optimization with Geometric Programming for Core Type Large Power Transformers

Abstract A good transformer design satisfies certain functions and requirements. We can satisfy these requirements by various designs. The aim of the manufacturers is to find the most economic choice within the limitations imposed by the constraint functions, which are the combination of the design parameters resulting in the lowest cost unit. One of the earliest application of the Geometric Programming [GP] is the optimization of power transformers. The GP formalism has two main advantages. First the formalism guarantees that the obtained solution is the global minimum. Second the new solution methods can solve even large-scale GPs extremely efficiently and reliably. The design optimization program seeks a minimum capitalized cost solution by optimally setting the transformers geometrical and electrical parameters. The transformers capitalized cost chosen for object function, because it takes into consideration the manufacturing and the operational costs. This paper considers the optimization for three winding, three phase, core-form power transformers. This paper presents the implemented transformer cost optimization model and the optimization results.

Characterization of Peltier Cell for the Use of Waste Heat of Spas

This research shows an overview of geothermal power generation and common methods used to harness it. In this way, the semiconducting method with thermoelectric devices is proposed to generate electricity by the use of waste heat of spas. Nowadays thermoelectric power generation is not so common due to its implementing costs. On the other hand, many places have no conditions to generate geothermal power by using the common methods because of the low water temperature. Thus, semiconducting method can be another choice for these places. This research also shows economic availability for thermoelectric power generation.

Core-form transformer design optimization with branch and bound search and geometric programming

The optimization of power transformers is one of the earliest applications of geometric programming. This approach works well with shell-form transformers, and the constructed models can be solved accurately with the new interior point method based solvers. However, a less well-known fact is that this kind of modeling becomes problematic in the case of core-form transformers. This paper shows a new metaheuristic solution to circumvent the main obstacle which is the calculation of short-circuit impedance.

Impact of the Cooling Equipment on the Key Design Parameters of a Core–Form Power Transformer

Abstract The first step in the transformer design process is to find the active part’s key design parameters. This is a non-linear mathematical optimisation task, which becomes more complex if the economic conditions are considered by the capitalisation of the losses. Geometric programming combined with the method of branch and bound can be an effective and accurate tool for this task even in the case of core-form power transformers, when formulating the short-circuit impedance in the required form is problematic. Most of the preliminary design methods consider only the active part of the transformer and the capitalised costs in order to determine the optimal key design parameters. In this paper, an extension of this meta-heuristic transformer optimisation model, which takes the cost of the insulating oil and the cooling equipment into consideration, is presented. Moreover, the impact of the new variables on the optimal key design parameters of a transformer design is examined and compared with the previous algorithm in two different economic scenarios. Significant difference can be found between the optimal set of key-design parameters if these new factors are considered.

A Generalized Geometric Programming Sub-problem of Transformer Design Optimization.

The first step in transformer design optimization is to solve a non-linear optimization task. Here, not only the physical and technological requirements, but the economic aspects are also considered. Large number of optimization algorithms have been developed to solve this task. These methods result the optimal electrical parameters and the shape of the core and winding geometry. Most of them model the windings by their copper filling factors. Therefore the transformer designer’s next task, to find out the detailed winding arrangement, which fits to the optimization results. However, in the case of large power transformers, the calculation of some parameters like: winding gradients, short-circuit stresses etc., needs the knowledge of the exact wire dimensions and winding arrangement. Therefore, an other optimization task should be solved. This paper shows how this sub-problem can be formulated and solved as a generalized geometric program.