Utilization of dissipated heat of power transformers

The aim of the article is to provide the reader with the basic concept of the transformer’s heat utilization where a proposed technical solution anticipates the installation of an additional oil-water heat exchanger (ODWF) in the transformer\u27s cooling system. An increase in the transformer’s cooling capacity lowers the oil temperature and reduces the transformer’s loss of life expectancy. In order to estimate the transformer’s oil temperature profile, as well as the heat power potential at the water side of the ODWF cooler, a numerical investigation was performed on the 150 MVA 220 / 115 kV transformer unit which operates in Podlog substation in Slovenia

Magnetic water treatment for scale control in heating and alkaline conditions

Magnetic water treatment (MWT), an alternative solution for scale control, is discussed with emphasis on the construction of the magnetic devices and the mechanism of MWT influence on the scale formation. Two applications in high-temperature and high-pH conditions are presented. The treatment noticeably reduced the scale thickness on the heating spiral and removed preciously precipitated scale from hot tap-water outlet pipeon the walls in the zone with heated alkaline water, instead of hard scale, only thin, brittle coating was formed. The morphology analyses showed the acceleration of aragonite nucleation and raised formation of fine suspended particles

Utilization of dissipated heat of power transformers

The aim of the article is to provide the reader with the basic concept of the transformer’s heat utilization where a proposed technical solution anticipates the installation of an additional oil-water heat exchanger (ODWF) in the transformer\u27s cooling system. An increase in the transformer’s cooling capacity lowers the oil temperature and reduces the transformer’s loss of life expectancy. In order to estimate the transformer’s oil temperature profile, as well as the heat power potential at the water side of the ODWF cooler, a numerical investigation was performed on the 150 MVA 220 / 115 kV transformer unit which operates in Podlog substation in Slovenia

Magnetic Fluids’ Heating Power Exposed to a High-Frequency Rotating Magnetic Field

Magnetic fluids are superparamagnetic materials that have recently been the subject of extensive research because of their unique properties. Among them is the heating effect when exposed to an alternating magnetic field, wherein the objective is to use this property in medicine as an alternative method for the treatment of tumors in the body. The heating effect characterization for the alternating magnetic field (AMF) has been studied widely, whilst for the rotational magnetic field (RMF), no systematic study has been done yet. In this article, we present the characterization of the heating power of magnetic fluids in a high-frequency rotational magnetic field. The results show similar behavior of heating power or specific absorption rate characteristics as in AMF

Assessment of magnetic fluid losses out of magnetic properties measurement

In this paper an improved measurement system for experimental assessment of magnetic fluid losses is presented. When fluid is exposed to AC magnetic field, three different losses mechanisms are activerelaxation, hysteresis and resonance mechanism. In this paper not individual contributions where studied but combine acting which can be determine as specific power losses (SPL). SPL of the sample is obtained for a variety of amplitudes and frequencies of magnetic field with presented method of measurement of field parameters where results revealed f H2 dependence for fixed temperature of the sample. Temperature dependence of SPL is examined with calorimetrical measurements, where heating of magnetic fluid at fixed value of applied field and various frequencies is examined and results revealed linearly decreasing temperature dependence

Design and optimization of a spherical magnetorheological actuator

Recently, an increasing number of electromagnetic devices have been using smart fluids. These include ferrofluids, electrorheological fluids, and magnetorheological (MR) fluids. In the paper, magnetorheological fluids are considered for use in a spherical actuator for haptic applications. An approach is presented to the design and optimization of such a device, using finite element method modelling linked with differential evolution (DE). Much consideration was given to the construction of the objective function to be minimized. A novel approach to objective function assembly was used, using reference values based on the model design and created with parameters set to the midpoint values of the selected range. It was found to be a useful strategy when the reference values are unknown. There were four parameters to be optimized. Three of them gravitated towards the boundary value, and the fourth (actuator radius) was somewhere in between. The value of the objective function reached a minimum in the range of actuator radius between 42.9880 mm and 45.0831 mm, which is about a 5% difference in regard to the actuator radius. Three passes of optimization were performed with similar results, proving the robustness of the algorithm

Finding a Crack’s Position and its Parameters on the basis of Non-Destructive testing, using Eddy Currents

The purpose of this paper was to find the geometry of a crack within a conductive plate and its parameters, on the basis of non-destructive testing, using eddy currents. The input data represents the measured values of magnetic flux density within the centre of the excitation coil. The position of a crack can be determined by taking into consideration any change in the magnetic flux density between the measured points. The depth and width are determined through the use of a finite-element model. These calculations are the basis for determining a function that explains how magnetic flux density changes if the depth or width has changed. After wards, through the Newton-Raphson iterative procedure using the finite-element method calculation results, the crack depth and width can be obtained. The suitability of the presented method was verified by the experimental example