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The importance of the transformers is that we Sirba much as boththe single phase and three

phase in, their operation is to reduce the voltage generated by the

company we electraca of Guatemala.

In high tancion cables is where transformers have more work as we decrease to seventy-

five thousand volts which conpone thecanbio of voltage transformers is that in the primary

coil has acurrent where it enters more and have

the secondary coils corientedisminuñe the hundred and twenty two forty volt or most of the

houses that is the service they consume.

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1 In developing the docunmental of transformers is to giveinformation on the great work they

do for all people who useelectric power.

2 The transformers generally work more in high retention that are responsible to all the

homes are single phase with the energyservisio appropriate for your own life.

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Topics pages

Transformers……………………………………………………………………………….6

Mutual Inductance…………………………………………………………………...…...7

Coupling of three-phase transformers in parallel…………………………………..8

Types of transformers……………………………………………………………………10

Distribution transformer…………………………………………………………………12

Dry transformers encapsulated in epoxy resin……………………………………..13 Integral Filling Hermetic transformers………………………………………..….…..14 Rural transformers………………………………………………………………….…....15 Underground transformers…………………………………………………………….15

Protected Auto Transformers………………………………………………………….16

AUTOTRANSFORMERS…………………………………………………………………18

CURRENT TRANSFORMER TT / CC…………………………………………………..19

POTENTIAL TRANSFORMER TT / PP…………………………………………………21

Constant current transformers……………………………………………………......23

Furnace Transformers…………………………………………………………………..23

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Transformers Grounding……………………………………………………………….23

mobile transformers………………………………………………………………….….24

Transformers for radio………………………………………………………………….24

Transformers for rectifiers………………………………………………………..…...25

special transformers………………………………………………………………..…...25

Transformers trials………………………………………………………………………27

other transformers……………………………………………………………………….28

PHASE TRANSFORMER………………………………………………………………..33

GENERAL……………………………………………………………………………..…..34

Connecting three-phase alternating current………………………………………35

delta Connection…………………………………………………………………….….35

star Connection…………………………………………………………………………35

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Transformers

The transformer is a static device electromagnetic type having two or more windings coupled by a mutual magnetic field (core) and is used to convert one or more systems ca in one or more systemsa.c. of different voltage. The application of the transformers can raise or lower the voltage,varying the number of phases and in some cases even vary the frequency of the ac The ability to transmit electrical signals fromone winding to another by electromagnetic induction was discovered by M. Faraday.

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Mutual Inductance.

Electromagnetic effects produced between two circuits that are close, ie when the respective magnetic fields of the sameinfluence each other, have been included under the heading ofmutual inductance and mutual inductance. These phenomena are of great use in electronics, radio and TV. Where powertransformers represent a typical example of the mutual inductance between two circuits.

In order to better interpret the effect of mutual induction, let us turnto Figure 1 below, which represents an inductor L1, fed by an alternating current and one inductor L2 which we consider is located near the first, so to be influenced by aquel.Evidentementemagnetic field, closing the circuit on L1, flow through this windingan alternating current, which in turn give rise to a variablemagnetic field. As L2 is close, this magnetic field will exert its action on itself, creating an emf on L2 inductors.

The voltage present on L2, will cause a current flow through the galvanometer will be charged interleaved. Therefore, L2, in turn,will cause a new magnetic field due to the emf induced, and thisnew magnetic field will also affect L1, which was the one who gave origen.De will result therefore affected the respectiveinductances L1 and L2 in their values. The closer they aretogether both windings, the greater the mutual effect caused.Figure 1 - Mutual induction between two magnetically coupledcoils.

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Coupling of three-phase transformers in parallel

Principle of operation. The basis of operation of a transformer is also the electromagnetic induction. In the figure shown in this text illustrates the fundamental transformer consisting of an iron coreand two windings referred to primary and secondary. The core provides a path for the magnetic field and is usually constructed of a large number of thin plates of special steel. The primary is the recipient of the power line and the secondary is the one who gives power to the load.

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Types of transformers

Power transformers:

Description:

Substransmisión and are used for power transmission in high and medium voltage. Apply in substations, power generation and large users. General Features:

Are built on standard powers from 1.25 to 20 MVA, at voltages of 13.2, 33, 66 and 132 kV. and frequencies of 50 and 60 Hz

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Distribution transformer

It is called distribution transformers, power transformers generallyequal to or less than 500 kVA and voltages less than or equal to 67 000 V, both single and three phase. Although most of these units are designed for mounting on poles, some of the higher power sizes above 18 kV classes are built for mounting in stations or on platforms. Typical applications are fed to farms, residences, public buildings or warehouses, shops and malls.

Here are some types of distribution transformers:

Description: They are used in outdoor or indoor electrical power distribution, medium voltage. They apply in urban areas, industries, mining,oil, great shopping and all activities that require intensive use ofelectricity. General Features: They are manufactured in standard powers from 25 to 1000 kVAand primary voltages of 13.2, 15, 25, 33 and 35 kV. They are built in other primary voltages as individual customer specifications.Are provided at frequencies of 50-60 Hz voltage variation is performed by an external switch operated with no load.

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Dry transformers encapsulated in epoxy resin

Description:

Used indoors for power distribution, medium voltage, in places where confined spaces and safety requirements in case of firepreclude the use of oil-cooled transformers. They apply in large buildings, hospitals, industries, mining, large shopping centers and any activity that requires the intensive use of electricity.

General Features:

Its main feature is that they are cooled in air with Class Finsulation, using epoxy resin as a protection of the windings, being unnecessary any post-installation maintenance. They are manufactured in standard power from 100 to 2500 kVA, primary voltages of 13.2, 15, 25, 33 and 35 kV and frequencies of 50 and 60 Hz

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Integral Filling Hermetic transformers

Description: They are used in outdoor or indoor electrical power distribution, medium voltage, being very useful in places where space islimited. They apply in urban areas, industries, mining, oil, great shopping and all activities that require intensive use of electricity. General Features: Its main feature is that by not carrying oil expansion tank is maintenance free, this construction being more compact than the traditional one. They are manufactured in standard power from 100 to 1000 kVA, primary voltages of 13.2, 15, 25, 33 and 35 kVand frequencies of 50 and 60 Hz

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Rural transformers Description: Monopole are designed for installation in suburban electrificationmonofilament nets, two and three wire, 7.6, 13.2 and 15 kV. In three-wire networks can be used as an alternative transformers3 phase or single phase.

Underground transformers applications Transformer proper construction to be installed in chambers at any level and can be used where it can dip of any kind.

features

Power: 150 to 2000kVA High voltage: 15 or 24.2 KV

Low Voltage: 216.5 / 125, 220/127, 380/220, 400/231V

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Protected Auto Transformers

applications

The processor incorporates components for distribution system protection against overloads, short circuits in the secondary network and internal faults in the transformer, for this high voltage fuses poseee and low voltage circuit breaker, mounted internally in the tank, high voltage fuses and low voltage circuit breaker. Forsurge protection the transformer is equipped with lightning protection device for external fixation in the tank.Características

Power: 45 to 150KVA High voltage: 15 or 24.2 KV

Low Voltage: 380/220 or 220/127V

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AUTOTRANSFORMERS

Auto-transformers are typically used to connect two transmission systems voltages, often with a delta tertiary winding. Similarly,auto-transformers are suitable as plant transformers when you want to feed two different transport systems. In this case the deltatertiary winding is a winding connected to the generator full capacity and the two transport systems are connected to thewinding autotransformer. The autotransformer has not only undernormal transformer losses, but their smaller size and weight allow the transport of higher powers.

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CURRENT TRANSFORMER TT / CC

Current transformers are used to sample the line current and reduce it to a safe level and measurable standard for ranges of instruments, measuring devices, or other measuring and controldevices. Certain types of current transformers protect the instruments to short circuit occur.

The values of the current transformers are:

Rated load: 2.5 to 200 VA, depending on their function. Rated: 5 and 1A on the secondary side. relationships are defined as primary current secondary current. Relations typical of acurrent transformer could be: 600 / 5, 800 / 5, 1000 / 5.

Usually these devices come with a suitable ammeter to the turns ratio of current transformers, for example, a transformer 600 / 5 is available with an ammeter graduated from 0 - 600A.

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POTENTIAL TRANSFORMER TT / PP

A transformer winding is especially a high voltage primary and a secondary low voltage. Is rated very low and its sole purpose is to provide a sample power system voltage to be measured withinstruments included.

Furthermore, since the main objective is the sampling of voltage should be particularly accurate as not to distort the true values. You can get potential transformers of various levels of accuracy,depending on how accurate your readings should be for eachspecific application.

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Constant current transformers A constant current transformer is a transformer that automaticallymaintains a nearly constant current in the secondary circuit under varying load impedance, when the primary is fed by anapproximately constant voltage source. The most common type, the provision of "voice coil," has separated primary and secondary coils, which are free to move among themselves, thusvarying the magnetic leakage reactance transformer. There substation types available that provide comprehensivecompact models, which carry the necessary accessoriesincluding control and protection of the transformer. The standard accessories include a solenoid switch primary protection. againstopen circuit, fuses or circuit breakers with fuses on the primary and surge arresters on the primary and secondary. Constant current transformers static type have no moving partsand operate on the principle of a resonant network. This networktypically consists of two inductive reactance and two capacitivereactance equal each to the supply frequency. With such a network, the secondary current is independent of the impedance of the connected load, but is directly proportional to the primary voltage.

Furnace Transformers

Furnace transformers supplying power to electric arc furnaces,induction rates,

resistance, submerged arc and open arc. Thesecondary voltages are low, sometimes less than 100 V, buttypically several hundred volts. The size range varies from a fewkVA to over

50 MVA, with the secondary currents in excess of 60 000 A. The high currents are obtained by connecting in parallelseveral sections of winding. The current is collected

by internalrods and carried through the transformer cover by bars or by high current terminals.

Transformers Grounding

A grounding transformer is a transformer designed mainly for the purpose of providing a neutral to ground effects. It can be a two-winding unit with the secondary winding connected in delta andstar connected primary winding that provides neutral groundeffects or may be a three-phase autotransformer windingsingle-star windings interconnected, ie in zig-zag.

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mobile transformers

Mobile transformers and mobile

substations. Transformers orautotransformers phones are usually mounted on trailers andhave built-arrester and separate sections. A mobile substationalso has switchgear and metering equipment and protection. The unit is moved by road pulled by tractors. State and federalregulations on road transport limit the maximum size and weight.The mobile units are used to restore power in emergencies, to allow maintenance without interruption of service, to provideservice during major construction and to reduce investment in the system.

The mobile unit is designed so that it is a multi-purpose compact unit that provides maximum power in kVA, for the weight

Transformers for radio

Power transformers. The purpose of the power transformerapplications in radio receivers is to vary the tension of the home network to a level that, when applied to a vacuum tube orsemiconductor rectifier (either half wave or full wave ) and is properly filtered, can be used to feed the bias voltages and currents for the active devices (valves, transistors, etc..) radio.The power transformer can also be used to change the supply voltage to a suitable value for filaments of the valves or fixturesthat may be on the radio.

Audio frequency transformers. Can be used three types of audiofrequency transformers in radio receivers: input, output andintermediate stages. In the normal receiver only uses the output transformer. The coupling between amplifier stages is achieved by common impedance input circuits and output amplifier stages. Input transformers. Work between the voltage source a.c. (most commonly the last intermediate frequency amplifier in a radio)and the first vacuum tube or transistor amplifier audio amplifier.The turns ratio for this transformer is determined by the normal stress applied on the primary and the desired value of voltage to be applied to the grid of the first valve or the base of thetransistor.

Transformers intermediate stages. All this before the input transformer to apply to processors of intermediate stages, with the exception that the intermediate stages transformers are used between stages of amplification audio amplifiers.

Output transformers. Operate between the last stage vacuum tubeamplifier transistors 0 audio and charging circuit, which is theradio speaker coil. Normally, the output transformer for a poweroutput stage has a ratio gearbox, because the speaker impedance is relatively low compared to the impedance of theoutput of an amplifier, whether tube or transistor.

RF transformers. This term is used to describe a class of transformers that operate at a much higher frequency of the audio range. This is the carrier frequency of the received radio signal,

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or in super-heterodyne radios, is the difference between theincoming carrier frequency and the oscillator frequency of the radio. This frequency difference is called the intermediate frequency and processors through which it passes are calledintermediate frequency transformers.

RF transformers perform essentially the same functions as theaudio frequency transformer (turns ratio determined by thedesired tension), but have three important differences. As mentioned above, work with much higher frequencies. In addition, they operate with powers considerably lower than the audiotransformers. Finally, one or both windings of a transformer RFare often shunted by a capacitor, so that forms a tuned circuit that attenuates all frequencies less than desired.

Transformers for rectifiers

Rectifier transformers to supply power to the rectifiers to the ACinput voltage required for output voltage d.c. desired. They are built in sizes that go up to 15 000 kVA and sometimes more. Thesecondary voltage is generally low, varying from less than 50 V, for some electrolytic processes, up to 1000 V for other applications. The secondary current is generally high and can reach many thousands of amperes

Transformer connections can be used to produce phase lags toget 12, 24 or even more, in order to reduce current harmonics inthe ac input Auxiliary transformers can be used or connections between the phase windings of the rectifier transformersthemselves. When using two secondary windings (as in thedouble-star circuit) must have the same impedance between the primary and each secondary winding to obtain the switchingangles and dc voltages equal in the two secondary circuits.

special transformers

Special application transformers Distribution transformers are generally dry type usually used with the primary circuits connected to low voltage distribution, to power lighting loads and small loadsto even lower voltages. There are transformers for primaryvoltages, 120, 240, 480 and 600 V, with power ratings from 25 VAto 500 kVA, 60 Hz

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Control transformers are isolation transformers and constant voltage dry type. Generally used with the primary winding circuitsconnected to low voltage distribution 600 V or less. Proper

selection of a control transformer facilitate the correct powersupply with reduced voltage lighting loads and control up to 250VA.

The transformers are similar to machine tool control transformerswith capacities up to 1500 VA for localized lighting for machine control devices such as solenoids, contactors, relays, bothportable and fixed tooltips. Primarily used to provide 120 Voutputs from 240 to relay 480 V at 60 Hz also available for operation at different voltages with 25 and 50 Hz

Class 2 transformers are isolation transformers dry type suitable for use in Class 2 circuits of the National Electrical Code. These transformers are generally used in remote control, small powersupply and signal circuits for driving stamps, campaigns, furnacecontrols, valves, relays, solenoids and the like. They are the primary units to 120 V limiter on both the type and the type energyis not limiting.

Signalling transformers are isolation transformers, gearboxes,constant voltage dry type, which are generally used with theirprimary windings connected or distribution networks to supply low voltage signaling systems not subject to the limitations of Class 2 circuits . Circuits exist for 120 or 240 V They carry a selection ofoutput voltages of 4, 8, 12, 16, 20 or 24 V, properly connectingthe four output terminals. There are units up to 1000 VA. Transformers for luminescent tubes, to power neon or other gases, are made in sizes ranging from 50 to 1650 VA. The ranges of the secondary voltages are between 2 000 and 15 000 V. The voltage depends on the length of the tube forming the circuit, ie the greater the length of the tube, the more tension is needed. The power delivered by the processors is between 18 and 120 mA.

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For ignition transformers are dry type transformers, highreactance, used to ignite gas burners or domestic fuel oil. Suchtransformers are limited to primary voltages of 120 or 240 V. Thesecondary voltages are limited to 15 400 V and typically willrange from 6 000 to 14 000 V. The range of nominal currents in the secondary goes from 20 to 28 mA and the power of 140 to 430 VA.

Transformers for toys are down transformers, the low voltagesecondary type, whose main purpose is to supply power toelectrically operated toys. They are usually portable and because of its intended use, gets special attention in regard to buildingsafety and fire hazard elimination, the entrance to the primary winding by construction should be limited to 660 W, even when the winding secondary is shorted, a condition that must be supported without creating a fire hazard. Such transformers are not authorized to voltages above 150 V primary and secondaryvoltages may not exceed 30 V between any two output terminals.

Transformers trials

For testing transformers, used for testing high voltage at low frequency, have been developed for higher voltages to enable the study of transport applications tensions growing. It often takes tensions of 1 500 000 or more volts. Units have been built for 1000 kV relative to ground, but usually it is cheaper to obtain such tensions connecting two or more units 'cascade' or 'chain'.The transformers for testing, are usually designed for short term applications. However, for special applications may require a power of several thousand kVA and time of application may be continuous.

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Current Transformer typical laboratory

Current Transformer typical laboratory

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Laboratory three-phase transformer

Laboratory single-phase transformer

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Common distribution transformer of the city

Utility distribution transformers

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Typical laboratory autotransformer

Power transformer

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Internal three-phase transformer

PHASE TRANSFORMER

equivalent Circuits

Almost all major systems of power generation and distribution of the world are today, three-phase AC systems. Since three-phase systems play an important role in modern life, it is necessary to understand how transformers are used in it.

Transformers for phase circuits can be constructed in two ways.These are:

1 Taking three-phase transformers and connecting them in a groupphase.

2 Making a three-phase transformer consisting of three sets ofwindings wound on a common core.

For the analysis of its equivalent circuit should represent eachsingle-phase transformer bank up phase by an equivalent circuit.As the effects of the capabilities of the windings and the harmonics of the excitation currents are negligible, you can use any of the equivalent circuits deduced for the case of single phase, the most useful for this study are shown in Figure 1 .

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GENERAL

Three-phase:

The three-phase electric power generation is the most commonand provides a more efficient use of drivers. The use of a three-phase electricity is common mostly for use in industries where many motors are designed for use.

The current phase consists of a set of three waveforms out of phase relative to each other 120 degrees, according to thediagram below.

The three phase currents are generated by alternators equipped with three coils or groups of coils wound on three sets of equally spaced pole pieces. The return of each of these circuits or phases is coupled to a point, called neutral, where the sum of the three currents is zero, so that transportation can be made using only three wires. The three-phase system is a class within the multi-phase power generation systems, but by far the most used. When you only need a single phase supply, as with domestic supply and distribution network is three-phase, it consists of four conductors, one for each phase and one for the neutral. In this case what you do is go handing the connection of different households between the three phases, so that the burdens ofeach stay as equal (balanced) as possible when connectingmany consumers.

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For security reasons, often connecting thread between the fifthmain breaker or fuse box and electrical building within each household, this thread is known as ground wire. The ground wireis connected to a bar or cobreclavada pica on the floor where it can be properly moistened to facilitate the best contact with the surrounding terrain. Spanish law prohibits electrical, for safety,that this ground was made through water or gas pipes.

In case of failure, accidental contact with the housing phase of an apparatus, the ground wire must support the current required toblow the fuse and isolate the faulty circuit, thus preventing the user from electrical shock can be damaged .

In addition to this protection, current legislation requires anysupply connection to each home through an enclosure comprisingat least a differential switch and one or more circuit breakers.

Connecting three-phase alternating current

Synchronous generators in each of the electromagnets areconnected to its own phase. You may wonder how it is possible, because in a three-phase system usually has only three wires(cables). The answer lies in the drawings above:

delta Connection

If we call the phase conductors L1, L2 and L3, then connect the first magnet to L1 and L2, L2 and L3 second and the third to L3 and L1.

This type of connection is called a delta connection, since driversare arranged in a triangle. There will be a voltage differencebetween each two phases which in itself is an alternating current.The voltage difference between each pair of phases will be larger than the voltage that defined on the previous page and in fact will always be 1.732 times the voltage (1.732 is the square root of 3).

star Connection However, there is another way in which a three-phase networkcan be connected: You can also connect one end of each of the three coils of an electromagnet to its own phase, and then connect the other end to a common connection for all three phases. This may seemimpossible, but consider that the sum of the three phases isalways zero and realize that this is indeed possible.

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