We can neglect these losses, as the percentage of these losses is very less as compared to iron and copper loss. F on sabbatical leave, university of alberta, edmonton, canada in large power transformers, the presence of stray currents in the structural elements near to. Hysteresis and eddycurrent losses of a transformer lamination viewed as an application of the poynting theorem by john barranger lewis research center summary an energyloss equation is developed based on the poynting theorem. Stray loss calculation of hvdc converter transformer. Loss prophet 53 2 magnetic shielding of the tank from hv side for the original design of investigated transformer 3 simulation model of transformer tank walls are shown surface impedance boundary condition enables calculations of stray losses in transformers, using a significantly reduced number of finite elements. Calculating stray losses in power transformers using. A large amount of higher harmonics will be generated in the load current when the transformer works in a converted way. Transformer losses are divided into losses in the windings, termed copper loss, and those in the magnetic circuit, termed iron loss. An ideal transformer is the one which is 100% efficient.
The stray losses are largely associated with the leakage flux and magnetic field surrounding the leads. Stray losses in the region surrounding high current bushings are estimated using 3d finite element fe simulations. Power transformer is the most important equipment in transmission. Index termstransformer, stray loss, clamping plate, loss reduction, optimization. Core losses are roughly constant from noload to fullload when feeding linear loads. The book deals with the following aspects of transformer engineering. The typical core is an assembly of laminated steel, and core losses are mostly related to magnetizing energizing the core.
The eddy current losses of a single conductor are treated using the rectangular and cylindrical. Stray load loss and mechanical loss in an electrical. The radial height of the conductor particularly affects the stray losses, which may be up to the fourth power. Particular attention has been paid to hot spots due to the distribution of stray current losses on each individual winding conductor of ctc cable. Due to this, the eddy current field is a nonlinear and nonsinusoidal one. This transformer hum is especially objectionable in transformers supplied at power frequencies and in highfrequency flyback transformers associated with television crts. Transformer losses and different types copper iron stray. Calculation of stray losses in continuously transposed.
Thus they take place all around the transformer instead of a definite place, hence the name stray. The stray losses in a transformer comprise winding stray losses, viz. Stray load loss analysis of induction motors due to. Download transformer engineering design technology and. Types of losses in a transformer there are various types of losses in the transformer such as iron loss, copper loss, hysteresis loss, eddy current loss, stray loss, and dielectric loss.
The results show that stray loss and local overheating can be reduced and eliminated effectively by adding magnetic shields. Inserts reduce the stray losses in the region of the tertiary voltage have been utilized in tank walls of poletype distribution bushings tvbs of the transformer. By convention, in dc machine stray load loss is normally taken as 1% of the rated output for rating of dc machine above 150 kw. Reduction of stray loss at transformer tank wall using conventional vertical magnetic shunts hot spots and eddy current losses reduction in the. Reduction of stray loss in power transformers using horizontal. Power transformers, stray losses, magnetic shields. Transformer losses types of energy losses in a transformer. In 10, a numerical method based on network approach is presented and it is used in 21 to model the effect of magnetic shunts on transformer stray. The stray losses are the component of the total load loss and they are produced by electromagnetic flux in the windings, tank, core, core clamping plates, magnetic shields, etc. Analysis of stray losses in power transformers by 3d magnetic. Transformers multiple choice questions and answers mcqs electrical engineering interview transformers viva lab manual pdf free download.
Khaparde helps you design better transformers, apply advanced numerical field computations more effectively, and tackle operational and maintenance issues. These losses, also known as noload losses, are present all the time the transformer is powered on regardless of whether there is any load or not. All current dependant losses in a winding other than the basic i 2r losses. Temperature reduction of power transformer tanks due to excessive stray losses abstract juan c. The biggest part of stray loss takes place in the transformer tank. The hysteresis losses occur because of the variation of the magnetization in the core of the transformer and the copper loss occurs because of the transformer winding resistance. Fifteenth national power systems conference npsc, iit. Prediction of hotspot location in a power transformer. Transformer considerations transformer types and classifications. It is appreciated that the computation of any component of stray losses of a transformer is intricate and involves a multitude of variables.
These losses are caused by the stray fields of the windings. Answer abhishek khandelwal leakage flux in a transformer produces eddy current in the conductors, these eddy current produces losses that is called stray loss of a transformer. Stray losses leakage inductance is by itself largely lossless, since energy supplied to its magnetic fields is returned to the supply with the next halfcycle. This means that the power supplied at the input terminal should be exactly equal to the power supplied at the output terminal, since efficiency can only be 100% if the output power is equal to the input power with zero energy losses. The copper losses represent the 2i r losses from the full load current in the phase windings, as well as stray losses due to induced eddy currents from leakage fluxes in the windings, core clamps, tank and other magnetic pathways. So there are two primary types of electrical losses in the transformer. The ability to predict these types of losses in the transformer is especially important if they occur in noload operation, i. Index termsfiniteelement method fem, magnetic shielding, power transformer, stray loss, wall shunts. Also, the effect of the lobetype magnetic shielding on the stray losses of power transformer using the 3d fem analysis is studied.
These shunts made of plates of transformer core steel, stacked to around 1omm thick, and mounted close to the transformer wall. Iron losses other than these, some small amount of power losses in the form of stray losses are also observed, which are produced due to the leakage of magnetic flux. This paper presents an analysis and computation of stray losses in the tank cover of a 75 mva threephase coretype transformer. Reduction of stray losses in flangebolt regions of large. A transformer design that takes into account the increase in naturally occurring stray losses caused by nonlinear loads. The work is associated to the practical approach and fem. Transformers have two major components that drive losses. Designers adopt various costeffective measures to minimize the losses and make the.
They are arranged so that they shield the wall from the leakage field produced by the unit when on load. Hence continuous research work is going on for transformer efficiency improvement. The measurement and evaluation of distribution transformer. In this paper, the calculation of stray losses distribution in core type transformer windings with continuously transposed conductor ctc cable based on multislice methodology is presented. These leakage fluxes link the metallic structural parts, tank etc. Losses occurring in the transformer are core loss, copper losses and stray loss. Data from industry is taken up for the verification and validation of stray loss calculation. Temperature reduction of power transformer tanks due to. Stray losses include eddy and circulating current loss, loss due to high current. Calculation of r 1 and x 1 the resistive and reactive components of the positive sequence transformer impedance can be.
Load losses there are the losses in a transformer which are incident to load carrying. Electrical engineering multiple choice questions and answers. These losses cause standard transformers to dramatically overheat and substantially shorten design life. Transformer basicsworking principle,construction,types. The hysteresis losses occur because of the variation of the magnetization in the core of the transformer and the copper loss occurs because of the transformer.
Larger transformers are generally more efficient, and those of distribution transformer usually perform better than 98%. They are determined by subtracting the ohmic i2r component from the m. Transformer loss measurement systems need calibration proven, validated accuracy stray losses based on finite element method can be found in 11. Load losses are divided into i 2r losses and stray losses. The project is designed to implement the changes in materials being used for clamping rings in order to reduce the stray losses in distribution transformer.
Pdf the article discusses the eddy current losses generated in a transformer tank walls and other electrically conductive construction parts. Similarly, a transformer also has some losses called transformer losses. In this paper, we investigate the stray load losses of induction motors due to the harmonic magnetic fields caused by the stator and the rotor slot ripples. Calculation and control of stray losses in power transformer. More than 20% of the total load loss is the stray loss in power transformer structural components. Hotspot is majorly influenced by stray losses of the transformer, thus it is evaluated using fem.
Losses expressed in watts in a transformer that are incidental to carrying a load. Loss prophet 55 7 magnetic shielding of the tank from hv side for the optimal design of investigated transformer 8 stray losses for the optimal design of investigated transformer the results obtained for the final design of the magnetic shielding are presented in 8 total stray losses obtained for the original design were assumed to be 100 per. Designers adopt various costeffective measures to minimize the losses and make the transformer more. Frame loss frames yoke beams, serving to clamp the yoke and support the windings, are in a vicinity of stray magnetic. A basic transformer consists of two coils that are electrically separate and inductive, but are magnetically linked through a path of reluctance. Pdf stray losses in power transformer tank walls and construction. Pdf stray losses in power transformer tank walls and. These also take place in the metal parts around the leads. These assumptions may be modified based on guidance from the manufacturer of the transformer. In large rating transformer, the stray losses constitute about 2025% of the total load losses.
Tray losses in transformer outside the windings occur. For synchronous and induction machine, stray load loss is taken around 0. Due to under estimation of stray losses in power transformer 2, 3 hot spots are formed. Stray losses depend on design power transformer losses 4 1 2. Introduction stray losses include eddy and circulating current loss, loss due to high current field, and frame and tank losses. In this paper clamping plate loss distribution is shown. Power transformer load loss measurement gert rietveld ernest houtzager milos acanski dennis hoogenboom enrico mohns. Hence to match the loss capitalization stray losses shall be reduced. Hysteresis and eddycurrent losses of a transformer. Effects of these shields on stray loss and loss density of structure parts are discussed. In an electrical transformer, the power losses are occurred in the windings and cores of transformers due to heating and magnetic losses caused by eddy current loss, hysteresis loss, stray loss, dielectric loss, and other unwanted effects.
The transformer, clamp plates and tank walls data are given in 1. So the stray loss evaluation is an essential aspect to calculate hot spot temperature. In dry type transformers, the last two mentioned types of stray losses are absent. These additional losses are generally known as stray losses. The stray load loss is proportional to the square of the load current. Journal of theoretical and applied information technology. Abstract stray losses in transformer clamping plate can be a considerable part of the overall stray loss in transformer. It can be seen in this paper that with increase the amount of vuf% stray losses and eddy current density on tank wall increases. The eddy current losses calculation using shell element has been applied to a power transformer of 40 mva. The objective of this work is to calculate stray losses in magnetic structures of 400 mva single phases, 500 kv230 kv auto transformer and study the effect of cu shield, put to prevent box type. This analysis is used to predict the hotspot location in the power transformer. Pdf prediction of stray losses in furnace transformer. Stray losses in transformer clamping plate semantic scholar. Power transformer load loss measurement gert rietveld.
Generally caused by high losses, or reduced cooling. Stray losses in the tank cover are estimated for a level of overload of 30% considering transformers. There are various types of losses in the transformer such as iron loss, copper loss, hysteresis loss, eddy current loss, stray loss, and dielectric loss. A core and coil design that manages the dc flux caused by triplen harmonics. Stray losses include eddy loss in the conductor, eddy losses in structural paths in close proximity to outgoing conductor and the eddy loss in general in the structural parts. Low radial conductor heights foil thickness give rise to extremely low stray losses. Fem methodology is applied to calculate losses and temperature distribution, and several configurations of transformer shielding were considered during the. Pdf reduction of stray losses in tertiary voltage bushings. Sheet 19001 distribution drytype transformerslow voltage. Power transformers introduction to measurement of losses 9 3.
The distorted stray field gives rise to higher eddy current losses stray losses. Low voltage distribution transformers and the 2016. Impact of changing clamping plate position and brackets design, material and position on the stray losses was analyzed. The major power loss in transformers are caused by, copper loss. The validation of this analysis method is verified by team. The main principle of operation of a transformer is mutual inductance between two circuits which is linked by a common magnetic flux. Reduction of stray losses in distribution transformer. The stray losses in tank walls, yoke clamps, tensile plate of core limb and other electrically conductive construction parts of a transformer are computed using threedimensional time harmonic finite element method. Olivaresgalvan universidad autonoma metropolitana azcapotzalco, mexico d. The noload loss can be significant, meaning that even an idle transformer constitutes a drain on an electrical supply, which encourages development of low loss transformers. Novel techniques and their application charles sweetser technical service manager. It provides some references for the analysis of stray loss and optimization design in transformer.
After the evaluation of stray losses, the different methods to reduce the heating of transformer tanks are incorporated to avoid the heating of transformer tanks. Computation of transformer losses under the effects of nonsinusoidal currents amit gupta 1, ranjana singh 2 1 pg scholar, hvps, department of electrical engineering, jabalpur engineering college amit. Stray load loss and mechanical loss in an electrical machine. The load losses of the 200 kva transformers working at full load, when feeds balance linear load, is presented in table 4. Reduction of stray loss in power transformers using.
To calculate stray losses in stray parts of power transformer such as tank walls, flitch plate, clamps and bolts, an analysis method of fem is used. To calculate stray losses in stray parts of power transformer such as tank walls, flitch plate, clamps and bolts. But it shall be kept in mind that this is only an approximation as stray load loss cannot be calculated accurately. Kulkami, member, ieee transformer division svkgtone cpl crompton greaves ltd. Apr 25, 2018 by convention, in dc machine stray load loss is normally taken as 1% of the rated output for rating of dc machine above 150 kw. The development of domestic hvdc transmission system needs the hvdc transformer to perform better. Must read, losses in electrical machine core loss and eddy current loss. Reduction of stray losses in distribution transformer using. The load loss in the transformer consist of losses due to the ohmic resistance of windings and certain additional losses. The stray losses take place in the winding and metal parts surrounding the windings. Download free book transformer engineering design technology and diagnostics second edition by s. The shunts have a much lower loss characteristic than.
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