Characterization of Power Transformer Electromagnetic Forces Affected by Winding Faults

Electromagnetic forces in power transformer windings are produced by interaction between the leakage fluxes and current passing them. Since the leakage flux distribution along the windings height is in two axial and radial directions, so the electromagnetic forces have two components, radial and axial. There is a risk that a large electromagnetic force due to the short circuit or inrush currents, can cause the windings to be deform, rupture, and/or displace, if the transformer and winding holders structure is not designed or assembled properly. Also, these mechanical changes can damage insulation between two or more adjacent turns of a winding and so, produce the local inter-turn fault. Occurrence of any fault in windings will change the electromagnetic force distribution in transformers and will cause developing secondary faults. Hence, this contribution is aimed at characterizing the electromagnetic forces behavior in power transformers and determines the changes of force values after occurring winding mechanical and inter-turn. The study keeps at disposal a two-winding, three phase, 8 MVA power transformer, on their windings faults are imposed and investigated through the FEM analysis. The accuracy of the created FEM model is firstly validated using analytical methods for transformer healthy condition, and then the winding shorted turn fault along with the mechanical faults are considered using 3D FEM model. The extracted characteristic signatures attained to different type of winding faults is expected to be useful at the design stage of power transformers

Experimental and 3D Finite Element Analysis of a Slotless Air-Cored Axial Flux PMSG for Wind Turbine Application

In this research paper, the performance of an air-cored axial flux permanent magnet synchronous generator is evaluated for low speed, direct drive applications using 3D finite element modeling and experimental tests. The structure of the considered machine consists of double rotor and coreless stator, which results in the absence of core losses, reduction of stator weight and elimination of cogging torque. In addition, the generator output voltage is sinusoidal in low speed operation and has a linear relationship with rotor speed, which makes it a suitable option for wind turbine applications. The simulation results of the proposed generator coincide very well with the experimental results on a system realized in the laboratory

Agricultural growth linkages in Sub-Saharan Africa:

How much extra net income growth can be had in rural areas of Africa by increasing the spending power of local households? The answer depends on how rural households spend increments to income, whether the items desired can be imported to the local area in response to increased demand, and, if not, whether increased demand will lead to new local production or simply to price rises. For every dollar in new farm income earned, at least one additional dollar could be realized from growth multipliers, according to Agricultural Growth Linkages in Sub-Saharan Africa.Income Rural areas Africa., Agricultural development Africa., Agricultural policy Economic aspects., Households Zimbabwe., Social accounting., Africa sub-Saharan,

A comparison of two methods for estimating odds ratios: Results from the National Health Survey

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Investigations of the uniformity of X-ray laser media

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