Igor Tičar, Jože Pihler, Oszkár Bíró and Kurt Preis
The term “partial discharges” (PD) is a common term for various phenomena: discharges at points or edges of cylindrical conductors, in gases and gas insulated devices, liquid…
Abstract
The term “partial discharges” (PD) is a common term for various phenomena: discharges at points or edges of cylindrical conductors, in gases and gas insulated devices, liquid insulation materials, at borders between different insulation materials and, of course, in solid dielectrics. These phenomena result in insulation breakdowns, various disturbances to the environment, and after longer periods, some large‐scale failures. This paper presents the results of theoretical research of the behavior of a system of medium voltage covered conductors. This research work has been elaborated by the use of computer aided electric field calculations. For the confirmation of theoretical findings, practical measurements of partial discharges have been made.
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Oszkár Bíró, Kurt Preis and Igor Ticar
This paper aims at developing a computational technique to take account of the laminated nature of iron cores when computing their eddy current losses.
Abstract
Purpose
This paper aims at developing a computational technique to take account of the laminated nature of iron cores when computing their eddy current losses.
Design/methodology/approach
A method is presented to compute three‐dimensional eddy current distributions in laminated media by means of the finite element method. In a first step, the laminated medium is assumed to have an anisotropic conductivity with zero (or very low) value in the direction normal to the laminations. In a second step, the eddy currents within the laminates are computed by solving the quasistatic electromagnetic field individually in each sheet. In these essentially two‐dimensional analyses, the boundary conditions are taken from the three‐dimensional field distribution determined in the first step.
Findings
Comparisons with results obtained from a finite element model taking account of each laminate prove the validity of the method.
Research limitations/implications
The method is presented for linear media only. Taking account of nonlinearity is an important future topic.
Originality/value
Taking account of the laminations by treating the magnetic field distribution obtained from a homogenised model is a novelty of potential benefit to researchers developing methods of loss computation in laminated media.
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Igor O. Golosnoy and Jan K. Sykulski
The purpose of this paper is to access performance of existing computational techniques to model strongly non‐linear coupled thermo‐electric problems.
Abstract
Purpose
The purpose of this paper is to access performance of existing computational techniques to model strongly non‐linear coupled thermo‐electric problems.
Design/methodology/approach
A thermistor is studied as an example of a strongly non‐linear diffusion problem. The temperature field and the current flow in the device are mutually coupled via ohmic heating and very rapid variations of electric conductivity with temperature and applied electric field, which makes the problem an ideal test case for the computational techniques. The finite volume fully coupled and fractional steps (splitting) approaches on a fixed computational grid are compared with a fully coupled front‐fixing method. The algorithms' input parameters are verified by comparison with published experiments.
Findings
It was found that fully coupled methods are more effective for non‐linear diffusion problems. The front fixing provides additional improvements in terms of accuracy and computational cost.
Originality/value
This paper for the first time compares in detail advantages and implementation complications of each method being applied to the coupled thermo‐electric problems. Particular attention is paid to conservation properties of the algorithms and accurate solutions in the transition region with rapid changes in material properties.