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The purpose of this paper is to design a current transformer model based on the principle of B-dot. It can reflect the change of transmission line current and meet the requirement of automation and intelligence for current measurement in power system.

In this paper, a new type of current transformer is designed on the principle of B-dot, which has the structure of the inverse series of planar air core coils and the form of printed circuit board (PCB). With this structure, the current transformers can induce magnetic field quite well. The finite element simulation for the current transformer with n layers structure is conducted in the Maxwell, which help to optimize the design of the current transformer.

By setting up the experimental platform, the experiment of the current transformer is carried out. The results of the test show that the measurement accuracy can satisfy the requirement of measurement. Besides, the new current transformer has good transient characteristics and can meet the needs of the development of smart grid.

The new type of current transformer is based on the principle of B-dot, which is designed with a new type of non-contact PCB hollow coil current transformer. It has no iron core, no ferromagnetic effect and the phenomenon of ferromagnetic resonance. It has great progress in its insulation performance, volume and bandwidth response. In addition, the planar hollow coil of the inverse series structure can make the structure more accurate.

Depending on the load the flux‐density distribution inside power transformers core shows significant local variations due to stray fluxes which enter the transformer core. As saturation of the core has to be avoided the flux‐density distribution has to be determined early in the design stage of the transformer. This paper seeks to address these issues.

To determine the load dependent flux‐density distribution the operating point of the transformer is calculated considering linear and non‐linear material properties. The operating point is determined using a linearised lumped parameter model of the transformer under various load conditions. Considering non‐linear material properties the inductance matrix depends on the operating point and will be extracted by means of the FEM whenever the magnetic energy within the transformer changes notably.

This paper presents a numerical stable approach to calculate the operating point of a transformer by using the magnetic flux linkage as state variable for the coupled field problem.

The proposed approach uses a fixed time‐step to update the lumped parameters by means of the FEM. This results in long simulation times. In further research it is planned to implement an adaptive time‐step method based on the change of the magnetic energy.

A numerical stable approach to calculate the operating point of a transformer by using the magnetic flux linkage as state variable for the coupled field problem is proposed. The methodology is applied to a 2D model of a three‐phase transformer. However, it also can be applied to 3D FE models. Based on the calculated operating point, the flux‐density distribution can be determined and several post‐processing methods can be executed (e.g. determination of core losses, …).

The purpose of this paper is to consider a constructional solution of the combined instrument transformer: constructed so that the voltage part is a column transformer, which means that the magnetic circuit of it is open and situated into a composite insulator. The aim of this research was to achieve optimal configuration of open magnetic circuit of the column voltage transformer.

The authors made analyses of electromagnetic field distribution and computed the voltage error and phase displacement for many different cases of magnetic circuits of the column voltage transformers. The analyses of the electromagnetic field distribution and computations were carried out using the 3D field‐circuit method based on the finite‐element numerical method. The results were compared with tests of a real‐life model.

The result of research is the selection of the best constructional version of the column voltage transformer; the research also gives some guidelines for design and manufacture of this construction of combined transformers.

The paper is meant for constructors of instrument transformers and presents results of research into new constructional solutions of combined transformer.

The theoretical method of converting the magnetic circuit into an electric circuit is mature, but the way to determine the inductances in the electric circuit is not reliable, especially for the core working in saturation status, and it is impossible to determine the inductances by the transformer terminal measurements, as the measurement information is not enough to determine a number of inductances. This paper aims to propose an approach of calculating the reluctances.

In this paper, an approach of calculating the reluctances is proposed based on the numerical simulation of magnetic field in transformer with different values of current excitation. The reluctance of a core segment or air region as a branch of magnetic circuit is obtained by the magnetic energy and magnetic flux. By this way, all the reluctances as function of flux can be determined, and then the inductances can be determined. The reluctances and equivalent electric circuit of three-phase integrative transformer is determined, and its validation is proved in the paper.

The single phase example shows that the proposed method has a good performances on analysis of the inrush current in deep saturation. The peak value of the inrush current derived from the proposed approach matches well with the results obtained by coupled circuit-FEM analysis, and the difference is about 4.8 per cent. For studies on dual models of single phase transformers, the leakage inductances have important effects on the peak value of the inrush current. The reluctances of three-phase transformer are calculated, and the equivalent circuit simulation results are slightly smaller than the coupled circuit-FEM simulation results.

Approach of calculating the reluctances based on the numerical simulation of magnetic field in transformer is proposed. The magnetic core and air space are divided into several segments, and the reluctance for each segment is calculated based on the energy in the region and the flux of the cross-sectional area. By applying various excitation currents, all the reluctances as function of flux can be determined, and then all the non-linear inductances including the non-linear leakage inductances are obtained. The proposed approach is reliable to determine a number of inductances in the dual electric circuit, especially for deep saturation status.

Significant achievements in ferrite material processing enable developments of many ferrite devices with a wide range of power levels and working frequencies, which make demands for new characterization and modelling methods for ferrite materials and components. The purpose of this paper is to introduce a modelling and measurement procedure, which can be used for the characterization of two‐port ferrite components in high frequency range.

This paper presents a commercially available ferrite component (transformer) modelling and determination of its electrical parameters using in‐house developed software. The components are measured and characterized using a vector network analyzer E5071B and adaptation test fixture on PCB board. The parameters of electrical equivalent circuit of the ferrite transformer parameters are compared with values extracted out of measured scattering parameters.

A good agreement between modelled and extracted electrical parameters of the ferrite transformer is found. The modelled inductance curves have the same dependence versus frequency as extracted ones. That confirms the model validity in the wide frequency range.

In‐house developed software based on proposed model provides inclusion of the ferrite material dispersive characteristics, which dominantly determines high‐frequency behaviour of two‐port ferrite components. Developed software enables fast and accurate calculation of the ferrite transformer electrical parameters and its redesign in order to achieve the best performance for required application.

The purpose of this paper is to investigate the possibility of utilizing printed circuit board (pcb) technology to manufacture coaxial transformers and to increase the predictability, accuracy and repeatability of the transformers leakage inductance.

The geometry of a coaxial transformer is approximated using pcb techniques. Several different geometries are presented with the outer coaxial conductor being approximated by discrete conductors varying from four to 36 in number. Finite element methods as well as experimental results are used to support the proposed ideas. A planar transformer is also analyzed in the same way to emphasize the design advantages offered by the proposed quasi‐coaxial transformer.

The proposed multi‐conductor structures can be applied as co‐axial transformers. The experimental values obtained for the leakage inductance of the coaxial structures correspond well to the predicted values. This is not the case for conventional planar structure where adjustments need to be made in the finite element analysis simulations to accommodate the shortcomings of the analytical calculations.

In applications where the prediction of the leakage inductance of a transformer is important, this method may be applied and has the advantage of conventional pcb manufacture techniques.

The purpose of this paper is to present a new type of equivalent scheme of multi‐winding transformers.

An inventory representation of relations between currents and flux linkages has been interpreted as a multi‐port purely inductive circuit.

An equivalent scheme in the form of a multi‐port circuit, and a method of its parameters determination from field computations.

Core losses are not considered in the multi‐port equivalent scheme.

A new equivalent scheme could become a basic tool for modeling multi‐winding transformers.

The introduced multi‐port equivalent scheme eliminates disadvantages of classical T‐type equivalent scheme of transformers.

The purpose of this paper is to examine the calculation of magnetic field distribution in the modular amorphous transformers under short‐circuit state including the flux by the voltage supplying. The magnetically asymmetrical transformer (amorphous asymmetrical transformer – AAT) has been compared also with the symmetrical one (amorphous symmetrical transformer – AST).

3D field problems were analyzed with total ψ and reduced ϕ potentials within the finite element method (FEM). The calculated fluxes have been verified experimentally.

The field method which includes voltage excitation is helpful for flux density (B) calculation and winding reactances determination, as well. Calculations and tests yield similar flux distributions in both AST and AAT constructions. One should emphasize that AAT is better for manufacturing and repairing.

Owing to very thin (80 μm) amorphous ribbon, the solid core has been assumed for computer simulations.

Employment of a field method for calculation of the innovative three‐phase amorphous modular transformers. New construction of amorphous transformer, i.e. AAT, has been manufactured at Opole University of Technology.

For the proposed coupling transformer, a magnetic bypass based on the virtual air gap principle is realized by inserting auxiliary windings in a return leg added to a standard transformer. With such a setup, it is able to act as a voltage regulator as well as protect the power electronics of the dynamic voltage restorer from electrical grid fault currents. This paper focuses on the electrical design part of the coupling transformer. It aims to explain how the behavior of the auxiliary windings electrical circuit of the magnetic bypass impacts the performances of the device.

The influence of the electrical auxiliary windings circuit configurations on the operation of the coupling transformer is studied by finite element analyses with nonlinear and isotropic magnetic materials.

A configuration for the realization of the electrical circuit of the auxiliary windings is determined according to the finite element simulation results to achieve the design of the coupling transformer whose magnetic core was previously designed.

By studying the operation of a special coupling transformer with nonlinear saturation phenomenon by finite element analyses, a to-do list of the electrical circuit parameters is described to design this device well.

The purpose of this paper is to determine the external magnetic field density of the traction transformer for EMU and to find the model for its computation.

The magnetic flux density in the surrounding region of the traction transformer was modeled and calculated using FEM. The transformer was modeled in a way that tank, clamps and current sources were taken into account. Most frequent operating modes for the basic 50 Hz current harmonic, and most represented higher harmonic of 1,950 Hz loading current, were analyzed.

Matching calculated and measured values were obtained on the finished transformer. The developed calculation has proved to be a useful tool for the stray field calculation outside this type of transformer. Calculated values of the flux density are lower then the maximum permitted values defined by the DIN VDE 0848 standard.

This paper presents a study of calculation compared to measurement of magnetic field density outside an oil immersed transformer.