Autor: wilder castro
Publisher: Joshua ordo単ez Interior design and production: Joshua ordo単ez, wilder ordo単ez page12 copyright2011 esclusive right n
I'm wilder geoovanyordo単ez castro is my second book in installation and maintenance of transformers in which we can see the engines for maintenance may of industrial estsoestudei my P rofessions at school in ITED
introduction The transformer is a device that converts AC power to a certain level of tension in otheralternative energy voltage level through electromagnetic interaction. It consists of two or more coils of conductive material, electrically isolated from each other and usually wrapped around the same core of ferromagnetic material. The only connection between the coils ofthe magnetic flux is common to set the kernel. Transformers are devices based on the phenomenon of electromagnetic induction and is composed in its simplest form, of two coils wound on a closed core, made of either soft iron or steel sheets stacked electrical appropriate to optimize the alloy magnetic flux. The coils or windings are called primary and secondary as applicable to the input or output of the system in question, respectively. There are also more windings transformers in this case, there may be a winding "tertiary" lower voltage than the secondary.
a transformer early…………….. 2
current ratio 3,4,5,6
aplicacion de los circuit……………………………………………..
diagram of the transformers……………… 11,12,13,14,15,16,
transformer equivalent circuit referred to the primary…………….20 constant determination……………………………………………….20.1 laprueba transformers shortcircui………………………………….20.2 Test diagram for a transformer short circuit………………………..…20.3 winding loss………………………………………………………………20.4
regulation…………………..………………20.5 power……………………………………………………………………..21 of the transformers……………………………………………………21.1 single…………………………………………………………………..21.2 and three…………………………………………………..…………22 TRANSFORMER construction……………….23.,24,,26 27,28
annexes…………………………...188.8.131.52 BiBliography………………………………...32. egrafia………………………………………33 glossary………………………….34,35,36,37
TRANSFORMER The invention of the transformer, dating from 1884, for application in transmission systems were at that time and had direct current technical and economic constraints. The first commercial AC purposes of distribution of electric power transformers used, was put into operation in the United States of America. In the year 1886 in Great Barington, Mass., in the same year, the peak voltage was transmitted at 2000 volts for alternating current at a distance of 30 kilometers, on a line built in Cerchi, Italy. From this small initial applications, the electrical industry in the world, has come in such a way that is now dedesarrollo of the people factor is an important part in this industry the transformer. The transformer is a device that has no moving parts, which transfers electrical energy from one circuit or another under the principle of electromagnetic induction. The transfer of energy usually makes changes in the values of voltages and currents. A transformer receives electrical power to a voltage value and surrender to a higher value, while a power transformer receives a high voltage value and commitment to a low value. Principles of electromagnetic induction. Electricity magnetism in an electromagnet, which is different from a permanent magnet and the magnetic field occurs only when the coils of wire wound around the core, carrying electric current. To determine the polarity of an electromagnet you can use the so-called left-hand rule. Principle of operation of the transformer. The operating principle of the transformer, can be explained by the so-called single-phase ideal transformer, ie a machine that is powered by a single phase alternating current.
Subject to further studies, the construction of the transformer, essentially we can say that a transformer consists of a core of magnetic material forming a closed magnetic circuit, and upon whose columns or legs localizandos windings, one called "primary"receiving power and the other side, which closes on a circuit which use energy delivery.The two windings are electrically asylum together. The voltage induces an electric generator, either when a coil moves through a magnetic field or when the field produced at the poles cut a stationary coil movement. In both cases, the total flow is substantially Contant, but there is a change in the amount of flux linking the coil. This same principle applies to the transformer, but in this case the coils and magnetic circuit are stationary (no movement), while continuously changing the magnetic flux. The change in the flow can be obtained by applying an alternating current in the coil.The current through the coil, varies in magnitude with time, and therefore, the flux produced by this current also varies in magnitude with time. The flow changing with the time into one of the windings E1 induces a voltage (in the primary). If contempt for ease, the voltage drop across the primary winding resistance, the value of E1 is equal and opposite to the applied voltage V1. From the law of electromagnetic induction, we know that E1 induced voltage in the primary winding and the rate of change of flow in the coil. We have two important relationships. V1 = - E1 ď Ą E1 N1 (0 / T)
The flow while changes in the primary coil, it changes in the secondary coil, since the two coils are located within the magnetic media, and then the rate of change of magnetic flux in both coils is exactly the same. This change in flow E2 induce a flow in the secondary coil that is proportional to the number of turns in the devanadosecundario N2. If one considers that there is no load connected to circuitosecundario, E2 induced voltage is the voltage appearing at terminals delsecundario, so you have two additional relationships. ď Ą E2 N2 (0 / T) E2 = V2 Given that weapons are coils wound on the same circuitomagnĂŠtico, the proportionality factors for the voltage equations are equal, so if you divide the equations for E1 and E2 have: E1 = N1 E2 N2 Furthermore, as numbers must be equal E1 and V2 or V2 - A above equation can be written as: V1 = Ng V2 N2 Current ratio. If a load is connected to the secondary of the transformer, the induced voltage Eghace carrying a current I2 in the secondary winding. Due to the current circulation is taken into the secondary winding magnetomotive force (MMF) I2 N2 opposite the primary N1
I1. It should be recalled that the voltage induced in the primary E1 is always directly proportional to flow 0 and is equal to the applied voltage V1, considering as before, all these values as effective. Since the applied voltage does not change in the core flow must be constant, any increase in the secondary current will be balanced by an increase in primary current, so that the flow produced by the current energizing the primary will constant real value during the operation of the transformer. Power transformers in the relatively small value, one can say that almost flux linking the primary winding is the same which links to the secondary and hence the load current or energizing represents only 2% or 3% the full load primary current can already say that the primary ampere-turns are equal to the secondary ampere-turns, ie: N1 N2 I = I2 I1 = N2 I2 N1 The application of the equivalent circuits. When transformers are used within a complex network to study the bound by terms of the distribution of the load, voltage drop, short circuit, etc.. appropriate, with regard to the now exposed on the operation of the transformer, considering with what is known as "Elcircuito equivalent" in its most complete form consists of a transformer "ideal" (N1/N2 ratio) connected to the resistors R0, R1 and R2 and reactance X0, X1 and X2. Equivalent diagram of a single-phase transformer. The resistance Ro represents the dissipative effect due to the load losses, R1 is the resistance of primary winding, the secondary R2. Similarly Xo represents the effect of absorption of the
magnetizing current, while X1 and X2 represent the effects of dispersed flows in the primary and secondary windings. For some studies, it is required to consider the effects of transformer core saturation and are negligible, while in others it requires greater precision and then to Ro and Xo are attributed to nonlinear properties. As mentioned before, for some studies it is convenient to refer to the values of voltages and currents referred to a wound on one side of the transformer, usually it is the primary supply. In these cases the equivalent circuit is simplified to a circuit "T".
Equivalent circuit of the transformer referred to LADOPRIMARIO. Secondary resistance and reactance referred to the primary winding according to the relations: R21 = R2 (N1) 2 N2 X21 = X2 (N2) 2 N2 Similarly primary resistance and reactance can refer alsecundario. Determining the constants of the transformer. The actual values of resistance and reactance of the windings of a transformer can be obtained from laboratory tests by measurements and some relatively simple calculations, which are the basis of the values used in the equivalent circuits are the basis of the values
used in the equivalent circuits. Some of these values or parameters obtained for the transformer transformer may not physically exist, but may help to understand the operation of the transformer. The short-circuit proof transformer. The short circuit test is to close or put on short circuit, ie, with negligible resistance connection, the terminals of a winding and feeding the other with a reduced voltage (applied in the form of a reduced value regulada_ voltage representing a small percentage of the winding voltage to feed, so that circulate in the windings rated currents. In this condition the rated currents are measured and the input power. Because the applied voltage is small compared to the rated voltage, load losses or core can be considered negligible, so that all the absorbed power is due to the Joule losses in the primary and secondary windings . Diagram for testing single-phase short circuit of a transformer. Wattmetor indicating power losses due to circulating currents in the primary and secondary windings. Short circuit connection between the terminals of the winding. Supply voltage of small value so as to circulate the currents I1, I2 nominal value of each winding. The applied voltage (Vc) is regulated and varies as noted above, to circulate full load current in the primary. From the measured values obtained "total impedance" transformer as: Vcc Zg I1
Where: I1 = primary rated current. Vcc = short circuit voltage applied to the test. Zt = total internal impedance winding referred to primary. This impedance is also known as equivalent impedance of the transformer.
Lost in the windings at full load. Because the flow is directly proportional to the voltage, the mutual flux in the transformer under test conditions of short circuit is very small, so that core losses are negligible. However, the current flowing through the resistance of the windings produces the same loss in this, that when operating at full load conditions, this is because in both windings and circulate the rated current. In the test circuit for short circuit, if the wattmetor is connected to the primary winding or power, then "measure" the losses in the windings and other losses have not considered, this value is taken of losses , one can calculate the "equivalent resistance" of the transformer as: RT Pcc (I1) 2 Where: Pcc = losses in the windings and are obtained the reading of the wattmeter. It must always bear in mind that the value of resistance Rt, is the arithmetic sum of the resistances in the primary and secondary windings. This value is determined from the equivalent circuit and for this reason is called "" the equivalent resistance of the transformer. "
The equivalent impedance of a transformer can be expressed in terms of the equivalent resistance and reactance as:
so that the equivalent reactance of the transformer is calculated as:
These values are usually referred to the high voltage winding, because they are accustomed to short circuit the low voltage winding, ie measurements are made in the high voltage winding. This is usually the standard test method. The main reasons for this: 1. The rated current of high voltage winding it is less than the rated current at low voltage winding. Therefore, less dangerous and moreover is easier to find measurement tools within the range. 2. Because the voltage is usually less than 5% of nominal voltage winding fed, you get a reading with a bending v贸ltimeto appropriate for the range of voltages that are measured. Transformer Regulation. The regulation of a transformer is defined as the difference between the load side voltage and full load, measured in terminals, this difference expressed as a percentage of full load voltage. To calculate load voltage must be taken into consideration the power factor of the load.
POWER AND PERFORMANCE OF TRANSFORMERS Single and Three Phase. The power transformers. As is known, single-phase AC power is given as the product of voltage and current and power factor, according to the expression. P = VI cos 9 This formula expresses the "real power" is measured in watts, the output voltage (only) by the current gives the so-called apparent power. P = VI The standards for transformers rated power when they speak, they refer to a power which is the product of the current and voltage in vacuum. The rated power is therefore an "apparent power" which is the same whether it is considered the primary winding or secondary winding. The reason for this is just conventional definition is due to the fact that the machine is characterized from the point of view of dimensioning. The benefits of an electric machine are limited by the heating of the components, which is caused by the losses you have. In particular, we have tFor the magnetic core, losses depend on the magnetic induction B, which is proportional to the voltage induced in the windings, the losses are proportional to the square of the current. The short-circuit proof transformer, enables load losses in the windings plan to give birth to them can be calculated for any load value.
The test called "open circuit" in the transformer, giving the value of so-called no-load losses and losses give the nucleus, as mentioned, consist of two parts, hysteresis loss and circulating current losses. In the open-circuit test, the winding that feeds is usually the low voltage, because the couple is the most convenient measurement.
The efficiency in transformers. In general, the efficiency of any electrical machine, is calculated as:
Efficient Pot. Exit = Pot. Exit Pot. Input Pot. Output + Losses Given that the capacity of a transformer is based on its power output, this equation can be written as:
Efficient output = KVA x PF FP Perd KVA output. Core + forgiveness. windings Daily efficiency transformers. Depending on the application of the transformers are often used to operate 24 hours a day, even when the load is not continuous in the whole period of operation. Under these conditions a transformer has two concepts of efficiency, global full load condition and the other for different loads per day, ie the so-called
daily efficiency. The daily efficiency expressed as the ratio of energy output to energy input during the period of 24 hours. Three-phase transformers. Most three-phase distribution networks are also a number of commercial users and industrial systems make use of tfifรกsicos power, this makes it necessary to consider the importance of threephase electrical installations and consequently These three-phase transformers. The energy of a three-phase system can be transformed, either by means of three-phase transformers (forming a three-phase bank) or by using a three-phase transformer.For economic reasons, space in the facility and equipment reliability, we can say that in general, the solution is preferred to use three-phase transformers in the electrical systems that require this type of food. Three-phase transformers typically consist of a core having three legs, or columns, on each of which is arranged primary and secondary windings of the same phase. These windings for each of the phases that can be connected in star, delta Zig-Zag. The connections between the secondary windings may be identical or different from those that are used between the primary phases so that in theory may have nine combinations of connection. In practice you can use the following connections between the primary and secondary windings: Star-star, delta-star, star / zig-zag, star-delta, delta-delta.
Transformation ratio for three-phase transformers. When the primary and secondary windings of a three-phase transformer connections are different, the relationship between the two strains of empty (no load) at the terminals is not equal to the
ratio between the turns of primary and secondary stage.This depends on the types of connections and selected, because, as noted, each type corresponds to a specific connection between the voltages realization concatenated and the phase voltages. If we consider for example a transformer primary winding in delta and delta primary winding and secondary winding star. If designated by V1 and V2 voltages of the primary phase and secondary phase, respectively, and V1 and V2, concatenated voltages (indicated) in primary and secondary terminals, respectively. In the primary winding, being connected in delta we have: V1 = V1 In the star-connected secondary winding: V2 = 3 V2 V2 = 1.732, therefore, the relationship between the load voltages at the terminals will be: V1 = V1 1.732 V20 V20 So far, there has been talk of single-phase transformers, and in these, the relationship between primary and secondary voltages in vacuum is known as "transformation ratio" (is designated with the letter A) and this relationship is valid also for her number of turns primary and secondary N1 N2. If you want to give the meaning of ratio of the relationship between turns: he transformer core losses and the losses in the windings.
Relations between the coils in relation to type of connection of windings. Criteria for the selection of connections. The selection of the combination of the connections depends on economic considerations and the requirements imposed by the operation. For example, in the distribution networks that use three phase with neutral, it is necessary to use a star secondary windings, as they have a point for the neutral daccesible. In transformers with delta primary winding and secondary star / or primary and secondary star in Zig-Zag imbalances or imbalances in the load (where the phases are not equally loaded) less impact on the primary power line . With regard to economic effects, we can say as a general criterion that the delta windings are more expensive than those connected in star, requiring drivers to use smaller diameter or should employ a larger number of turns. Phase shift between the phases. In the three-phase transformers is important among other things, the possible phase shift of the voltage phase secondary to primary voltage., Which can affect the parallel connection of transformers. In the three-phase single-phase transformers, the three-phase transformers, primary and secondary windings have the same connection (eg star / star delta / delta) secudnria tension can this only in phase (A 00) or position phase, ie 180o. In contrast, transformers, three-phase windings mixed connection (eg star / delta, delta / star, star / zig-zag), the angular phase shift can never be 0 째 or 180th but must be a multiple of 30 째. Vectorially examining all combinations of three-phase connections, it appears that including the phase shift of 0 째, may have 12 different values of angular phase shift of 30 likes 30 degrees, the usual phase shift values are given in angular table.
TRANSFORMER CONSTRUCTION. General considerations. A transformer consists of two main parts: The magnetic core and windings, these are related to other elements for mechanical and electrical connections between different parts of the cooling system, the means of transport and the protection of the machine in general. provisions regarding the construction, the kernel determines relevant characteristic, so that a distinction is fundamental in the construction of transformers, depending on the shape of the nucleus and can be called CORE and the CORE COLUMNS TYPE shell type, other aspects to differentiate between types of transformers, as for example the cooling system, which establishes the form of heat dissipation therein, or in terms of their power and voltage applications such as power transformers classifieddistribution rate. The construction of the core. The magnetic core is made up of steel laminations with small percentages of silicon (about 4%) and so-called "magnetic laminations", these laminations are the property of having relatively low losses as a result of circulating currents and hysteresis. They consist of a set of laminations arranged in the shape and dimensions required.The reason for using silicon steel laminations in the cores of electrical machines is that the resistivity silicon material increases and then decreases the magnitude of the eddy currents or circulating and therefore losses in this connection. In the case of large power transformers are used so-called "glass plate oriented" with a thickness of several millimeters and contain between 3% and 4% silicon, obtained from hot-rolled material after rolling is cold, giving a final heat treatment to the surface thereof. This type of lamination when subjected to the flow in the direction of the laminations, magnetic properties have rolled better than "normal" silicon steel used for other types of
transformers. Elements of transformer cores. In the magnetic cores of transformers column are two main parts: "columns" or legs and "yokes". The columns are housed windings and yokes attached to each of the columns to close the magnetic circuit. Because the coils must be mounted under a certain procedure and remove when necessary for maintenance work, the cores that close the magnetic circuit, finishing at the same level in the part that is in contact with the yokes, or ridged. In both cases the cores are armed with "games" of laminations for columns and yokes which are assembled in layers of arrangements "even" and "odd". When using glass plates oriented, it is necessary that the joints between yokes and columns are carried out with slanting cuts to avoid cross paths flow lines with respect to such directions. When you have armed levels based on flip charts placed in "pairs" and "odd" the core is attached using screws and separated by means of clamping screws. As for the Yugos, refers not to be bound these windings can be, then, rectangular, although they can also take steps to improve cooling. Types of nuclei. As mentioned above, transformer cores laso basically grouped into the following categories: a) Type of core or columns. b) Type Battleship. c) Type of core or columns. There are different types of nuclei types column, which is characterized by the relative position of the columns and yokes. Core phase. We have two columns joined at the top and bottom by means
of a yoke, in each of these columns are embedded half of the primary winding and secondary windings half. Phase core. They have three columns arranged taste the same plane together in the upper and lower parts through yokes. Above each column are embedded primary and secondary windings of a phase. Magnetizing currents of the three phases are different from each other, mainly due to the magnetic circuit of the external columns is longer than that for the central column. This imbalance, taking into account that the magnetizing current of the three phases are different from each other, mainly due to the magnetic circuit of the external columns is longer than that for the central column. This imbalance, taking into account the load current is quite low, only influences the load operating conditions. Shell type. This type of armored core, has the advantage over the call type column, to reduce the stray magnetic, its use is more common in single-phase transformers. In armored core, the windings are located on the central column, and when it comes to small transformers, the laminations are made in dies. The forms of construction may be different and vary with the load. Hardware or armor. As mentioned before, the cores of the transformers have parts that comply with holding purely mechanical functions of the laminations and structures, or elements of these pairs are known as "hardware" or armor and complement components such as fiber glass or wood protection of the subjection of the yokes. The windings of the transformers. The windings of transformers so can be classified into low and high voltage, this distinction is of global nature and is important for the purposes of the practical realization of the windings due to the construction criteria for the realization of low voltage windings are than those used for high voltage windings. For constructive purposes, is not important function of a winding, ie primary or secondary, only the voltage matters which
should be expected. Another classification of the windings can be done in relation to the power transformer windings for this purpose are low-power transformers, for example from 1000 to 2000 VA transformer and medium and high power. The windings for transformers of low power are the easiest to perform. In this type of transformer primary and secondary windings are concentric and wound on an insulating one. Usually used enamelled copper wires, coil windings and overlays. Generally, the lower voltage winding is installed closer to the nucleus by interposing an insulating paper cylinder by spacers is installed concentrically higher voltage winding. The ends of the windings (also known as the beginning and end of the winder) are protected with insulating tube known as "spaghetti." Distribution transformer windings. In these processors, the difference between primary and secondary stress is remarkable, for example, transformed to pray distribution of 13200 volts to 220/127 utilization voltage volts due to these differences, different criteria are used to will be considered constructive in small transformers and low voltage windings are divided into low voltage and high voltage. Low voltage windings. Usually consist of a single spiral (sometimes two or three superimposed layers), with insulated rectangular wires. The driver is typically used to power small and have diameters no greater than 3 or 3.5 mm. The insulation of the conductors when they are cylindrical, can be cotton or paper, more rarely enamelled driver if the processors are not cooled by oil. For medium and large transformers power, it involves the use of sill plate or insulated copper, insulation is usually paper. In the event that the winding currents are higher transport either by manipulation waver in construction or to reduce eddy currents, one can construct the winding gift or plate of a parallel slab.
High voltage windings. The high voltage windings, is compared with the low voltage, many turns, and the current flowing through them is relatively low, so are copper conductor of circular section with diameter of 2.5 to 3.0 mm. With regard to structural characteristics, there are variations from manufacturer to manufacturer, there are basically two types, called "type coil" consisting of several layers of condutores, these reels have disc-shaped, these coils are connected, usually in seriesto give the total number of turns of one phase. The other type des-called "layers" consisting of a single multi-layer coil, the coil is of length equal to the number of coils that constitute the discoidal equivalent winding, usually the number of turns per layer in this type of winding is more than made up of several coils discoidal. As general rules, we can say that the first type (disk-shaped coils) gives greater ease of cooling and soaking up oil, because it has many channels of circulation, it also has the advantage of requiring smaller diameter conductors equivalent to otherwise, gives greater ease of construction. It has the disadvantage of being more slow in its construction. The disk-shaped coils are also known as "type cookie" in some cases, each form, a certain number of conductors arranged in layers and these layers isolated from each other by insulating paper, each coil at the end is "tied" with tape linen or cotton to give mechanical consistency and then given a bath of varnish and baked at a certain temperature, which acquires the necessary mechanical rigidity. Each coil is designed for a voltage not exceeding 1000-1500 volts, so to give the required voltage for a phase, should be placed several coils in series. Position of the windings. The arrangement of the windings in transformers, should be done in such a way that the best way to reconcile the two requirements that are contrastentes each other, isolation and reduced leakage flux. The first requires greater separation between windings, while the second requires that the primary s is the nearest
to the secondary. In practice, we reach a suitable solution of the problem with the arrangement of the windings inside and the following types: ďƒ˜ Concentric. ďƒ˜ Dual Concentric. ďƒ˜ Alternate. In the concentric type, each of the windings is distributed throughout the column the lower voltage winding is on the inside (closer to the nucleus) and isolated from the nucleus, and the higher voltage, for through insulating tubes (cardboard bakelite, bakelite, etc.).. In the arrangement of concentric double winding voltage above floor divides into two halves disposed respectively within and outside of each other. In the so-called alternating, the two windings are subdivided each into a tape number of coils that are arranged in alternating columns. The guiding considerations from the design standpoint, the arrangement of the windings, are those relating to cooling, insulation, leakage reactance and mechanical stress. With regard to insulation, the most convenient solution is represented by the simple concentric type because it requires a single layer of insulation between the windings, so this arrangement is advantageous in the case of high voltages. The so-called dual concentric's prerogative to lead to the leakage reactance value of about half that on the simple concentric. The alternating, however, allows several such reactors, dealing in a different way the positions of the two winding coils .. for mechanical loads are better alternate type provisions, allowing better support the transformer mechanical stress. Construction of the windings. As indicated above, the conductors used for the construction
of the windings, wire can be circular (as a diameter of between 0.2 and 0.4 mm) or slab of different measures. Depending on the type of turns of the coils can be constructed in two ways. ďƒ˜ Helicoidadl continuously. ďƒ˜ With separate coils (discoidal). The helical coils are made, usually when the driver used is hearth, all care must be taken is in the form of isolation from the core and possibly its mechanical constitution. This type of construction has certain limitations, in terms of isolation, even when you can build in layers, so that their practice is limited to low voltage windings. Coil construction discoidal (for windings with separate coils), usually done with the same number of turns per coil and is made of layers so as to limit the maximum voltage between turns of adjacent layers to a value between 200 and 300 volts with this are expected in general, and only in exceptional cases, the coil voltage is at most 1000 volts between layers separated by insulating paper. With regard to the position of the windings, transformers are of two types: concentric windings and windings alternate. In the case of concentric windings transformers, these, the primary and secondary windings are completely different and are mounted one inside the other flavor the nucleus, while, for reasons of privacy, especially the lower voltage winding closer to the nucleus . At higher power transformers and only exceptionally, one can divide the low voltage winding into two parts, so that one is close to the nucleus and the other is placed on the winding tension can, that is, is a dual concentric. The concentric arrangement of the windings, is the one with a wider field of application.
Whatever the type of winding, the construction of the coils is usually done on wooden or metal molds mounted on winding or unwinding whose type is different, depending mainly coil size to be built. In the case of small transformer coils that can be done in workshops windings, these coils are manual, and can eventually get to use lathes. When finished winding a coil before assembly should be given treatment and dried in a vacuum to remove any traces of moisture, and a process of impregnating insulating varnish and baked at a temperature which depends on the type of varnish and whose goal is to give mechanical consistency. External insulation of the windings. The primary and secondary windings must be insulated themselves aware generally that isolates using wooden separators, bakelite or similar insulating materials also meet cooling functions. MOORING SYSTEM VIA AXIAL winding opposite screw pressure. The isolation between the phase-phase transformer is made conveniently separating the columns, between which are interposed separators or diaphragms sometimes treated cardboard or bakelite. The external insulation between the phases is achieved through the nozzles that connect the terminals of the windings. Connections of the windings. When building a winding can be wound in the sense of right or left (with respect to the direction of clockwise), it was observed that a current has a certain sense, it produces a magnetic flux in the opposite direction, have a built winding to the left or right winding, this should be taken into account, to prevent the connections are
made, they have opposing flows or voltages induced opposites. In general, each manufacturer takes a winding one-way for all coils, both secondary and primary. In the two-column single-phase transformers, the flow is direct and opposite in the two columns, this means there must be a form of connection. Change in the transformation ratio. In a distribution network, the voltage is not exactly the same at all points, because the voltage drop depends on the distance from the feed point and the magnitude of the load. In order to use the distribution transformers at various points in the network and adapt to changes in tension, it provides one of the windings of a tap changer (The high voltage) so that they can increase or decrease the number of coils and thus vary the transformation ratio within limits, these limits are typically 5%.
ELECTRICAL MATERIALS USED IN CONSTRUCTION OF TRANSFORMERS. Electric conductors. The materials used as conductors in transformers like those used in other electrical machines, must be of high conductivity, since these are produced with the coils. The fundamental requirements to be met by conducting materials are as follows: 1. The highest conductivity possible. 2. The lowest possible temperature coefficient electrical resistance. 3. Adequate mechanical strength. 4. Must be reducible and malleable. 5. Must be readily weldable.
6. Have adequate corrosion resistance. The resistivity or specific resistance, the breakdown voltage, the dielectric permittivity and hysteresis in addition to the dielectric properties should also consider the mechanical properties and its ability to withstand the action of chemicals, heat and other elements during operation. The temperature and insulation materials. One of the factors that affect the lives of the isolates, is the operating temperature of electrical machines, this temperature is caused mainly by losses in the specific case of transformers, during operation, these losses are located in the following main elements: The core or magnetic circuit, here the losses are caused by the hysteresis effect and circulating currents in the laminations, are dependent on the induction, ie, influencing the supply voltage. Windings, the losses here are mainly due to the Joule effect and to a lesser extent by eddy currents, these losses in the windings are dependent on the load on the transformer. Losses are also presented in the joints or connections which are also known as "hot spots" as well as in tap changers. All these losses cause heating in transformers, and removes this warming is due to values that are not dangerous pair isolates Also, through the application of different means of cooling. In order to maintain in a reliable and satisfactory operation of electrical machines, heating of each of its parts, must be controlled within certain predefined limits. The losses in an electrical machine are important not so much constitute a source of inefficiency, but because they represent an important source of elevated temperature
parts of a transformer
The transformer is a device that has no moving parts, which transfers electrical energy fromone circuit or another under the principle of electromagnetic induction. The transfer of energy usually makes changes in the values of voltages and currents. A transformer receives electrical power to a voltage value and surrender to a higher value, while a power transformer receives a high voltage value and commitment to a low value.
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Glossary Electricity magnetism in an electromagnet, which is different from a permanent magnet and the magnetic field occurs only when the coils of wire wound around the core, carryingelectric current. To determine the polarity of an electromagnet you can use the so-calledleft-hand rule. The voltage induces an electric generator, either when a coil moves through a magnetic field or when the field produced at the poles cut a stationary coil movement. The resistance Ro represents the dissipative effect due to the load losses, R1 is the resistance of primary winding, the secondary R2. Secondary resistance and reactance referred to the primary winding according to the relations: Wattmetor indicating power losses due to circulating currents in the primary and secondary windings The applied voltage (Vc) is regulated and varies as noted above, to circulate full loadcurrent in the primary voltage Vcc applied to the short circuit impedance Zt = total internalwinding referred to This impedance is also known as equivalent impedance of the transformer.