Dariusz Koteras

Simulation of forces and 3-D field arising during power autotransformer fault due to electric arc in HV winding

Forces and three-dimensional magnetic fields in high-voltage winding due to an internal short circuit in a power autotransformer are calculated with the computer package OPERA 3D. The considered damage was caused by an electric arc. The materialized deformation of the winding part confirms the simulation results.

Amorphous modular transformers and their 3D magnetic fields calculation with FEM

Purpose – 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).Design/methodology/approach – 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.Findings – 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.Research limitations/implications – Owing to very thin (80 μm) amorphous ribbon, the solid core has been assumed for computer s...

The influence of the leg cutting on the core losses in the amorphous modular transformers

Purpose – In a modular transformer with a wounded amorphous core, the authors should make some cutting to limit the eddy currents in its magnetic ribbon. The purpose of this paper is to deal with 3D magnetic field analysis, including the eddy currents induced by varying frequency of power. The influence of the core leg cutting on the power losses values, in the three variants of a one-phase modular transformer structure, has been presented. Design/methodology/approach – 3D field problems including eddy currents of various frequency were analysed using the electrodynamic potentials and V within the finite element method. The wave method and iterative one of the laminated core homogenization, have been employed. The values of the calculated losses have been verified experimentally. Findings – The reduction of the core losses by axial cutting of the transformer legs is an efficient approach for the loss limitation. The wave method is not acceptable for homogenization of the amorphous core for its operation a...

Electromagnetic and Temperature 3-D Fields for the Modular Transformers Heating Under High-Frequency Operation

Core losses in two different transformers under high-frequency (f=10 kHz) operation have been simulated using 3-D FEM modeling. For the first transformer, we assumed an amorphous core, while the ferrite core has been established for the second one. The equivalent electrical conductivity values have been assumed. The values of core losses were included into 3-D modeling of the temperature field. For both transformers, the temperature of the cores and windings was calculated versus the heating time. The calculation results have been compared with the ones from tests of our prototypes, and a good agreement has been obtained.

Calculation of the magnetic bearing parameters

3D finite element model of the active magnetic bearing is presented in this paper. Integral parameters of the magnetic field have been computed. The inductances of the bias and control coils have been determined. Some parameters of the magnetic bearings have been measured and compared with the calculated ones.

Three-dimensional magnetic field analysis of the 1-phase choke

The presents, the three-dimensional field analysis of the 1-phase choke. Two commercial packages OPERA 3D and MAXWELL 3D for field determination has been used. We compared the calculation results of magnetic flux density components. A good agreement has been achieved.