Transformer and Mission San Juan Capistrano: Difference between pages

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:''Another mission bearing the name '''San Juan Capistrano''' is the [[Mission San Juan Capistrano (Texas)|Mission San Juan Capistrano]] in [[San Antonio, Texas]].

:''This article is about [[electrical]] and [[electronics|electronic]] transformers. For other meanings, see [[Transformers]]''

{{Infobox Missions|

[[Image:PoleMountTransformer02.jpg|thumb|300px|right|Three-phase pole-mounted step-down transformer]]

image=Mission San Juan Capistrano 4-5-05 100 6588.JPG|

A '''transformer''' is an [[electricity|electrical]] device that transfers energy from one circuit to another purely by [[magnetic]] [[Inductive coupling|coupling]]. Relative motion of the parts of the transformer is not required for transfer of energy. Transformers are often used to convert between high and low [[voltage]]s, to change [[impedance]], and to provide electrical isolation between circuits.

caption=A view of Mission San Juan Capistrano in April of 2005. At left is the façade of the first adobe church with its added ''espadaña''. Behind the ''campanario'', or "bell wall" is the "Sacred Garden." The Mission has earned a reputation as the "''Loveliest of the Franciscan Ruins.''"|

name=Mission San Juan Capistrano|

___location=[[San Juan Capistrano, California]]|

originalname=''La Misión de San Juan Capistrano de Sajavit''&nbsp;<ref>Leffingwell, p. 37</ref>|

translation=The Mission of Saint John of Sajavit|

namesake=[[Giovanni da Capistrano|Saint John]] of [[Capestrano]]|

nickname="Jewel of the Missions"&nbsp;<ref>Young, p. 26</ref><br>"Mission of the Swallow"|

founded=[[November 1]] [[1776]]&nbsp;<ref>Leffingwell, p. 37</ref>|

foundedby=Father Presidente [[Junípero Serra]]|

foundingorder=Seventh|

militarydistrict=First|

nativetribe=[[Acjachemem|Juaneño]]|

owner=[[Roman Catholic Church]]|

placename=''Quanís Savit, Sajivit''&nbsp;<ref>Ruscin, p. 195</ref>|

currentuse=Chapel / Museum|

Coor dms={{coor dms|33|30|10|N|117|39|42|W|}}|

NHL=[http://www.nationalregisterofhistoricplaces.com/CA/Orange/state2.html #NPS&ndash;71000170]|

NRHP=[[September 3]] [[1971]]|

CHL=[http://ohp.parks.ca.gov/default.asp?page_id=21445 #200]|

website=http://www.missionsjc.com|

}}

'''Mission San Juan Capistrano''' was founded on [[All Saints|All Saints Day]] ([[November 1]]), [[1776]]. Named for a 15th-century [[Theology|theologian]] and "warrior priest" who resided in the [[Abruzzo]] region of [[Italy]], San Juan Capistrano has the distinction of being home to the oldest building in California still in use, a [[chapel]] built in 1782; known alternately as "Serra's Chapel" and "Father Serra's Church," it the only extant structure wherein it has been documented that the padre officiated over [[mass]].<ref>Young, p. 23</ref> The founding document on display within the Mission is also the only known surviving founding paper signed by Father Serra. One of the best known of the Alta California missions, the site was originally consecrated on [[October 30]], [[1775]] by Father [[Fermín Lasuén]] but was abandoned due to unrest among the indigenous population in San Diego.<ref>Yenne, p. 72</ref>

== Introduction ==

The transformer is one of the simplest of electrical devices. Its basic design, materials, and principles have changed little over the last one hundred years, yet transformer designs and materials continue to be improved. Transformers are essential in high voltage [[power transmission]] providing an economical means of transmitting power over large distances. The simplicity, reliability, and economy of conversion of voltages by transformers was the principal factor in the selection of [[alternating current]] power transmission in the "[[War of Currents]]" in the late 1880's. In electronic circuitry, new methods of circuit design have replaced some of the applications of transformers, but electronic technology has also developed new transformer designs and applications.

The success of the settlement is evident in its historical records. Prior to the arrival of the missionaries, some 550 natives were scattered throughout the local area; by 1790, the number of converted [[Christians]] had grown to 700, and just six years later nearly 1,000 "neophytes" (recent converts) lived in or around the Mission compound. 1,649 [[baptism]]s were conducted that year alone, out of the total 4,430 souls converted throughout the Mission's lifetime. An estimated 2,000 former inhabitants (mostly [[Native Americans in the United States|Native Americans]]) are buried in unmarked graves in the Mission's [[cemetery]] (''campo santos''), as are the remains of Father (later [[Monsignor]]) [[St. John O'Sullivan]], the man credited with recognizing the property's historic value and working tirelessly to conserve and rebuild its structures. Father O'Sullivan is buried at the entrance to the cemetery on the west side of the property, and a statue raised in his honor stands at the head of the crypt. The surviving chapel also serves as the final resting place of three padres who passed on while serving at the Mission: Father José Barona, Father Vincent Fuster, and Father José Rafael Oliva are all entombed beneath the sanctuary floor.

Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage [[microphone]] to gigawatt units used to interconnect large portions of national power grids, all operating with the same basic principles and with many similarities in their parts.

The Mission entered a long period of gradual decline after [[secularization]] in 1834. Numerous efforts were made over the years to restore the Mission to its former glory, but none met with great success until the arrival of Father O'Sullivan in 1910. Restoration efforts continue to this day; "Serra's Chapel" is still used for religious services, and over half a million people visit the [[landmark]] every year. In 1984 a modern church complex was constructed just north and west of the Mission compound; the design is patterned after the old stone church, but twenty percent larger. Its 85-foot high main [[rotunda]] and 104-foot high bell tower make it the tallest building in town; [[Pope John Paul II]] conferred the rank of [[Minor Basilica]] to this facility on [[February 14]], [[2000]].

Transformers alone cannot do the following:

*Convert [[Direct current|DC]] to [[Alternating current|AC]] or vice versa

*Change the voltage or current of DC

*Change the AC supply [[frequency]].

However, transformers are components of the systems that perform all these functions.

[[Image:1916 Rexford Newcomb sketch -- Mission San Juan Capistrano.jpg|thumb|350px|right|Artist Rexford Newcomb's conception of Mission San Juan Capistrano in its heyday. The intact "Great Stone Church" is depicted at the far right.<ref>Newcomb, p. 16</ref>]]

==Basic principles==

===An analogy =Prehistory==

The first humans are thought to have made their homes among the southern valleys of California's coastal mountain ranges some 10,000 to 12,000 years ago. The earliest of these people are known only from archaeological evidence. Relatively much is known about the native inhabitants in recent centuries, thanks in part to the efforts of the Spanish explorer [[Juan Rodríguez Cabrillo]], who documented his observations of life in the coastal villages he encountered along the Southern California coast in October of 1542.<ref>Yenne, p. 8</ref> Fray Gerónimo Boscana, a Franciscan scholar who was stationed at San Juan Capistrano in 1812, compiled what is widely considered to be the most comprehensive study of prehistoric religious practices in the San Juan Capistrano valley. Religious knowledge was secret, and the prevalent religion, called ''[[Chinigchinix|Chingichngich]]'', placed village chiefs in the position of religious leaders, an arrangement that gave the chiefs broad power over their people.

The transformer may be considered as a simple two wheel 'gearbox' for electrical voltage and current. The primary winding is analogous to the input shaft and the secondary winding to the output shaft. In this comparison, voltage is equivalent to shaft speed, current to shaft torque. In a gearbox, mechanical power (speed multiplied by torque) is constant (neglecting losses) and is equivalent to electrical power (voltage multiplied by current) which is also constant. The gear ratio is equivalent to the transformer step up or down ratio.

==History==

=== Flux coupling laws===

===The Mission Era (1769 &ndash; 1833)===

[[Image:Transformer3d col3.svg|right|thumb|400px|An idealised step-down transformer showing resultant flux in the core]]

[[Image:Mission San Juan Capistrano 4-5-05 100 6535.JPG|thumb|250px|right|A statue of Father Junípero Serra and an Indian boy, sculpted by '''Tole van Rensalaar'''; the work was commissioned in 1914 by Father St. John O'Sullivan to depict the meeting of the two cultures. Father O'Sullivan acted as the subject for Serra, and local resident Clarence Mendelson was the model for the boy.]]

A simple transformer consists of two electrical [[Electrical conduction|conductor]]s called the '''primary winding''' and the '''secondary winding'''.

If a time-varying voltage <math>{v_P}\, </math> is applied to the primary winding of <math>N_P\, </math> turns, a current will flow in it producing a [[magnetomotive force]] (MMF). Just as an [[electromotive force]] (EMF) drives current around an electric circuit, so MMF drives magnetic flux through a magnetic circuit. The primary MMF produces a varying [[magnetic flux]] <math>\Phi_P\, </math> in the core (shaded grey), and induces a back [[electromotive force]] (EMF) in opposition to <math>{v_P}\, </math>. In accordance with [[Faraday's law of induction|Faraday's Law]], the voltage induced across the primary winding is proportional to the rate of change of flux :

Father Juan Crespí authored the first written account of actual interaction between Franciscan friars and the indigenous population after his expedition traveled through the region on [[July 22]], [[1769]]. The group officially named the area after [[Mary Magdalene|Santa Maria Magdalena]] (though it would also come to be called the ''Arroyo de la Quema'' and ''Cañada del Incendio'', "Wildfire Hollow").<ref>Kelsey, p. 9</ref> The Mission site was chosen as a logical halfway point between [[San Gabriel]] and [[San Diego]]. San Juan Capistrano is one of the few missions to have actually been founded twice (another being [[Mission La Purísima Concepción]]); the site was first established Father Fermín Lasuén and Father Gregório Amúrrio on October 30, 1775 near an [[Native Americans in the United States|Indian]] settlement named ''Sajivit''; unfortunately, [[Mission San Diego de Alcalá]] came under Indian attack eight days later.<ref>Wright, p. 37</ref> Since it was feared at the time that any hostile action by the natives against the few burgeoning outposts might break [[Spain]]'s tenuous hold on [[Alta California]], the fathers quickly buried the San Juan Capistrano Mission bells and the expedition returned to [[Presidio of San Diego|El Presidio de San Diego]] in order to quell the uprising.

:::<math>{v_P} = {N_P} \frac {d \Phi_P}{dt}</math>

One year later Fathers Serra and Lasuén returned to once again begin work on the Mission at San Juan Capistrano; once there, they uncovered the bells and discovered that a wooden cross that had been erected during the original dedication was still standing. Due to an inadequate water supply the Mission site was subsequently relocated approximately three miles to the west near the Indian village of ''Acágcheme''.<ref>Kelsey, p. 10</ref> According to a report filed in 1782 by Father Pablo Mugártegui, "''...the site was transferred to that which it occupies today, where we have the advantage of secure water...this transfer was made on [[October 4]], [[1778]].''"&nbsp;<ref>Mission San Juan Capistrano; retrieved on March 29, 2006</ref> The new venue was strategically placed above two nearby [[stream]]s, the [[Trabuco Canyon, California|Trabuco]] and the San Juan. [[Mission San Gabriel Arcángel]] provided [[cattle]] and neophyte labor to assist in the development of new the Mission.

Similarly, the voltage induced across the secondary winding is:

In 1778, the first [[adobe]] ''capilla'' (chapel) was blessed. It was replaced by a larger, 115-foot long house of worship in 1782, which is believed to be the oldest standing building in California. Known proudly as the "Serra Chapel," it has the distinction of being the only remaining church in which the padre is known to have officiated ([[Mission San Francisco de Asis|Mission Dolores]] was still under construction at the time of Serra's visit there). Father Serra presided over the confirmations of 213 people on October 12 and 13, 1783; divine services are held there to this day. The centerpiece of the chapel is its spectacular ''[[retablo]]'' which serves as the backdrop for the altar. A masterpiece of [[Baroque]] art, the altarpiece was hand-carved of 196 individual pieces of cherry wood and overlaid in [[gold leaf]] in [[Barcelona]] and is estimated to be 400 years old. It was originally imported from Barcelona in 1806 and later donated by Archbishop John Cantwell of [[Los Angeles]] (the building had to be enlarged to accommodate this piece). Although the ''retablo'' had been relayered over the centuries, most of the original gilding remains underneath the modern materials; extensive restoration was begun in June, 2006. By the time of the chapel's completion, living quarters, kitchens (''pozolera''), workshops, storerooms, soldiers' barracks (''cuartels''), and a number of other ancillary buildings had also been erected, effectively forming the main ''cuadrángulo'' (quadrangle).

:::<math>{v_S} = {N_S} \frac {d \Phi_S}{dt}</math>

[[Image:1916 Rexford Newcomb plan view -- Mission San Juan Capistrano.jpg|thumb|300px|left|A plan view of the Mission San Juan Capistrano complex (including the footprint of the "Great Stone Church") prepared by architectural historian [[Rexford Newcomb]] in 1916. <ref>Newcomb, p. 15</ref>]]

With perfect flux coupling, the flux in the secondary winding will be equal to that in the primary winding, and so we can equate <math>\Phi_P\, </math> and <math>\Phi_S\, </math>. It thus follows that:

California's first vineyard was located on the Mission grounds, with the planting of the "Mission" or "[[Criollo]]" grape in 1779, one grown extensively throughout Spanish America at the time but with "an uncertain European origin." It was the only grape grown in the Mission system throughout the mid-1800s. The first winery in Alta California was built in San Juan Capistrano in 1783; both red and white [[wine]]s (sweet and dry), [[brandy]], and a port-like [[fortified wine]] called [[Angelica wine|Angelica]] were all produced from the Mission grape. In 1791, the Mission's two original bells were removed from the tree branch on which they had been hanging for the previous fifteen years and placed within a permanent mounting. Over the next two decades the Mission prospered, and in 1794 over seventy adobe structures were built in order to provide permanent housing for the Mission Indians, some of which comprise the oldest residential neighborhood in California. It was decided that a larger, [[European]]-style church was required to accommodate the growing population. Hoping to construct an edifice of truly magnificent proportions, the padres retained the services of expert [[Mexican]] stonemason '''Isidoro Aguílar'''.<ref>Camphouse, p. 30</ref> Aguílar took charge of the church's construction and set about incorporating numerous design features not found at any other California Mission, including the use of a [[dome]]d roof structure made of [[Rock (geology)|stone]] as opposed to the typical flat wood roof. His elegant roof design called for six [[Vault (architecture)|vaulted]] domes (''bovedas'') to be built.

:::'''<math>\frac{v_P}{v_S}=\frac{N_P}{N_S}.</math>'''

Work was begun on "The Great Stone Church" on February 2, 1797. It was laid out in the shape of a cross, measuring 180 feet long by 40 feet wide with 50-foot high walls, and included a 120-foot tall ''campanile'' ("bell tower") located adjacent to the main entrance that could be seen for miles around. The building sat on a [[foundation (architecture)|foundation]] seven feet thick. Construction efforts required the participation of the entire ''[[Wiktionary:neophyte|neophyte]]'' population. Stones were quarried from gullies and creek beds up to six miles away and transported in carts (''carretas'') drawn by [[oxen]], carried by hand, and even dragged to the building site. [[Limestone]] was crushed into a powder on the Mission grounds to create a [[mortar (masonry)|mortar]] that was more erosion-resistant than the actual stones.

Hence in an ideal transformer, the [[ratio]] of the primary and secondary voltages is equal to the ratio of the [[coil|number of turns]] in their windings, or alternatively, the voltage per turn is the same for both windings. This leads to the most common use of the transformer: to convert electrical energy at one voltage to energy at a different voltage by means of windings with different numbers of turns.

[[Image:Mission San Juan Capistrano 4-5-05 100 6583.JPG|thumb|300px|right|A close-up view of the majestic ruins of Mission San Juan Capistrano's "Great Stone Church," dubbed the "[[American Acropolis]]" in reference to its classical [[Greco-Roman]] style.]]

The EMF in the secondary winding, if connected to an electrical circuit, will cause current to flow in the secondary circuit. The MMF produced by current in the secondary opposes the MMF of the primary and so tends to cancel the flux in the core. Since the reduced flux reduces the EMF induced in the primary winding, increased current flows in the primary circuit. The resulting increase in MMF due to the primary current offsets the effect of the opposing secondary MMF. In this way, the [[Electric power|electrical energy]] fed into the primary winding is delivered to the secondary winding.

Unfortunately, Señor Aguílar died six years into the project. His work was carried on by the padres and their charges, who made their best attempts to emulate the existing construction. Lacking the skills of a master mason, however, led to irregular walls and necessitated the addition of a seventh roof dome. The church was finally completed in 1806, and blessed by Fray Estévan Tapís on the evening of September 7<ref>Yenne, p. 75</ref>. The sanctuary floors were paved with diamond-shaped [[tile]]s, and [[brick]]-lined niches displayed the statues of various saints. It was by all accounts the most magnificent in all of California and a three-day feast was held in celebration of this monumental achievement. Tragedy struck the settlement when on [[December 8]], [[1812]] (the "Feast Day of the Immaculate Conception of the Blessed Virgin") a series of massive [[earthquake]]s shook Southern California during the first Sunday service. Twelve years earlier a minor earth [[tremor]] had hit, causing only superficial damage to the work in progress.<ref>Chase and Saunders, p. 27</ref> The 1812 [http://www.data.scec.org/chrono_index/wrightwd.html Wrightwood Earthquake] racked the doors to the church, pinning them shut. When the ground finally stopped shaking, the bulk of the nave had come crashing down, and the bell tower was completely obliterated. Forty-two worshippers from the local [[Acjachemem]] Nation (referred to as Juaneños by the [[Spaniards]]) who were attending mass were buried under the rubble and lost their lives, and were subsequently interred in the Mission cemetery. This was the second major setback the outpost had suffered, and followed severe storms and flooding that damaged Mission buildings and ruined crops earlier in the year.

Neglecting losses, for a given level of power transferred through a transformer, current in the secondary circuit is inversely proportional to the ratio of secondary voltage to primary voltage. For example, suppose a power of 50 watts is supplied to a resistive load from a transformer with a turns ratio of 25:2.

*P = E&middot;I (power = electromotive force &middot; current)

50 W = 2 V &middot; 25 A in the primary circuit

* Now with transformer change:

50 W = 25 V &middot; 2 A in the secondary circuit.

[[Image:San Juan Capistrano 1880 painting.jpg|thumb|300px|right|''Misión San Juan de Capistrano'' by [[Henry Ford (illustrator)|Henry Chapman Ford]], 1880. The work depicts the rear of the ruined "Great Stone Church" as well as part of the mission's ''campo santos''. A portion of "Serra's Church" is also visible at right.]]

In a practical transformer, the higher-voltage winding will have more turns,of smaller conductor cross-section, than the lower-voltage windings.

The padres immediately returned to holding services in Serra's Church. Within a year a brick ''campanario'' ("bell wall") had been erected between the ruins of the stone church and the Mission's first chapel to support the four bells salvaged from the rubble of the campanile. As the [[transept]], [[Sanctuary#Sanctuary as a sacred place|sanctuary]] (''reredos''), and ''sacristia'' ([[sacristy]]) were all left standing, an attempt was made to rebuild the stone church in 1815 which failed due to a lack of construction expertise (the latter is the only element that is completely intact today). Consequently, all of the construction work undertaken at the Mission grounds thereafter was of a strictly utilitarian nature. Father José Barona and Father Gerónimo Boscana oversaw the construction of a small infirmary ([[hospital]]) building (located just outside the northwestern corner of the quadrangle) in 1814, "for the convenience of the sick." It is here that Juaneño [[Medicine man|medicine men]] used traditional methods to heal the sick and injured.<ref>Engelhardt, p. 57</ref> [[Archaeological]] excavations in 1937 and 1979 unearthed what are believed to be the building's foundations.

Since a DC voltage source would not give a time-varying flux in the core, no back EMF would be generated and so current flow into the transformer would be unlimited. In practice, the series resistance of the winding limits the amount of current that can flow, until the transformer either reaches thermal equilibrium or is destroyed.

On [[December 14]], [[1818]] the [[France|French]] [[privateer]] [[Hippolyte de Bouchard|Hipólito Bouchard]], sailing under an [[Argentina|Argentine]] flag, brought his ships ''La Argentina'' and ''Santa Rosa'' to within sight of the Mission and sent forth an envoy with a demand for provisions. The [[garrison]] [[soldiers]] were aware that Bouchard (today known as "California's only [[pirate]]") had recently conducted raids on the settlements at [[Monterey, California|Monterey]] and [[Santa Barbara, California|Santa Barbara]], so the demand was rebuffed and threats of reprisals made.<ref>Yenne, p. 77</ref> In response, ''Pirate Buchar'' ordered an assault on the Mission, sending some 140 men and a trio of cannon to take the needed supplies by force.<ref>Jones p. 170</ref> The Mission guards engaged the attackers but were overwhelmed, and the privateers left several damaged buildings in their wake, including the ''Governor's house'', the ''King's stores'', and the barracks. A celebration is held annually to memorialize the event. Between 1820 and 1823 an ''estancia'' (station) was established a few miles north on the banks of the [[Santa Ana River]] to accommodate the Mission's sizeable cattle herd. The adobe structure built to house the [[Majordomo (domestic staff)|mayordomo]] and his men is known today as the [[Diego Sepúlveda Adobe]].

==== The Universal EMF equation ====

If the flux in the core is [[sinusoidal]], the relationship for either winding between its number of turns, voltage, [[magnetic flux density]] and core cross-sectional area is given by the universal emf equation:

[[Image:Mission san juan capistrano0001.jpg|thumbnail|300px|right|A [[Islamic architecture|Moorish]]-style fountain inside Mission San Juan Capistrano's central courtyard, built in the 1920s through the efforts of Father St. John O'Sullivan.]]

:::'''<math> E=4.44 \cdot f \cdot N \cdot a \cdot B</math>'''

[[Mexico]] gained its independence from [[Spain]] in 1821. The 1820s and [[1830s|30s]] saw a gradual decline in the Mission's status. Disease thinned out the once ample [[cattle]] [[herd]]s, and a sudden infestation of [[Mustard plant|mustard weed]] made it increasingly difficult to [[cultivate]] [[agriculture|crops]]. Floods and droughts took their toll as well. But the biggest threat to the Mission's stability came from the presence of [[Spanish people|Spanish]] settlers who sought to take over Capistrano's fertile lands. Over time the disillusioned Indian population gradually left the Mission, and without regular maintenance its physical deterioration continued at an accelerated rate.

Where '''<math>E\, </math>''' is the sinusoidal [[root mean square]] voltage of the winding, '''<math>f\, </math>''' is the [[frequency]] in [[hertz]], '''<math>N\, </math>''' is the number of turns of wire, '''<math>a\, </math>''' is the cross-sectional area of the core and '''<math>B\, </math>''' is the peak magnetic flux density in [[Tesla (unit)|tesla]]. The value 4.44 collects a number of constants required by the system of units.

Nevertheless, there was sufficient activity along [[El Camino Real (California)|El Camino Real]] to justify the construction of the [[Las Flores Asistencia]] in 1823. This facility, situated halfway between San Juan Capistrano and the Mission at [[Mission San Luis Rey de Francia|San Luís Rey]], was intended to act primarily as a rest stop for traveling clergy. During the same period the '''Diego Sepúlveda Adobe''' was established as an ''estancia'' (way-station) for the ''[[vaquero]]s'' ([[cowboys]]) who tended the Mission herds, in what today is the City of [[Costa Mesa, California|Costa Mesa]]. Following secularization, ownership passed to Don Diego Sepúlveda.

==Invention==

Although Governor [[José Figueroa]] (who took office in 1833) initially attempted to keep the mission system intact, the [[Congress of Mexico|Mexican Congress]] nevertheless passed ''An Act for the Secularization of the Missions of California'' on [[August 17]], [[1833]]. Mission San Juan Capistrano was the very first to feel the effects of this legislation the following year.

Those credited with the invention of the transformer include:

===The Rancho Era (1834 &ndash; 1849)===

* [[Michael Faraday]], who invented an 'induction ring' on August 29, [[1831]]. This was the first transformer, although Faraday used it only to demonstrate the principle of [[electromagnetic induction]] and did not foresee the use to which it would eventually be put.

[[Image:CHS.J3075.jpg|thumb|300px|left|The caretaker chats with guests beneath the shade of one of Mission San Juan Capistrano's courtyard arcades. The facility's advanced state of decay is evident.]]

* [[Lucien Gaulard]] and [[John Dixon Gibbs]], who first exhibited a device called a 'secondary generator' in London in 1881 and then sold the idea to American company [[Westinghouse Electric Corporation|Westinghouse]]. This may have been the first practical power transformer, but was not the first transformer of any kind. They also exhibited the invention in [[Turin]] in 1884, where it was adopted for an electric lighting system. Their early devices used an open iron core, which was later abandoned in favour of a more efficient circular core with a closed magnetic path.

* [[William Stanley (physicist)|William Stanley]], an engineer for Westinghouse, who built the first practical device in 1885 after George Westinghouse bought Gaulard and Gibbs' patents. The core was made from interlocking E-shaped iron plates. This design was first used commercially in 1886.

* [[Hungary|Hungarian]] [[engineer]]s [[Ottó Bláthy]], [[Miksa Déri]] and [[Károly Zipernowsky]] at the [[Ganz company]] in [[Budapest]] in [[1885]], who created the efficient "ZBD" model based on the design by Gaulard and Gibbs.

* [[Nikola Tesla]] in [[1891]] invented the [[Tesla coil]], which is a high-voltage, air-core, dual-tuned resonant transformer for generating very high voltages at high frequency.

The [[Mexican Congress]] passed ''An Act for the Secularization of the Missions of California'' on [[August 17]], [[1833]]. The Act also provided for the colonization of both Alta and Baja California, the expenses of this latter move to be borne by the proceeds gained from the sale of the mission property to private interests. Mission San Juan Capistrano was the very first to feel the effects of this legislation the following year. The [[Franciscans]] abandoned the Mission, taking with them most everything of value, after which the locals plundered the Mission buildings for construction materials. By 1835, little of the Mission's assets remained, though the manufacture of hides and tallow continued as described in [[Richard Henry Dana, Jr.|Richard Henry Dana's]] classic novel ''[[Two Years Before the Mast]]''.<ref>Young, p. 24</ref>

==Practical considerations==

San Juan Capistrano was officially designated as a [[secular]] Mexican [[pueblo]] in 1841, at which time those few who still resided at the Mission were granted sections of land to use as their own. Four years later the Mission property was auctioned off under questionable circumstances for $710 worth of tallow and hides to [[Englishman]] John "Don Juan" Forster (Governor [[Pío Pico]]'s brother-in-law, whose family would take up residence in the Friars' quarters for the next twenty years) and his partner James McKinley. More families would subsequently take up residence in other portions of the Mission buildings.

===Classifications===

[[Image:Polemount-singlephase-closeup.jpg|thumb|180px|right|Single phase pole-mounted step-down transformer]]

===California Statehood (1850 &ndash; 1900)===

Transformers are adapted to numerous engineering applications and may be classified in many ways:

[[Image:Mission San Juan Capistrano 4-5-05 100 6553.JPG|thumb|300px|right|Father José Mut's dining room as it is thought to have looked during his twenty-year stay at the Mission. Some years later, furniture maker and architect [[Gustav Stickley]] (the leading spokesperson for the American [[Arts and Crafts movement]]) would develop a reputation for fine, hand-crafted furnishings that were inspired by pieces such as these.<ref>Cathers, p. 45</ref>]]

* By power level (from fraction of a watt to many megawatts),

* By application (power supply, impedance matching, circuit isolation),

* By frequency range (power, audio, RF)

* By voltage class (a few volts to about 750 kilovolts)

* By cooling type (air cooled, oil filled, fan cooled, water cooled, etc.)

* By purpose (rectifier, arc furnace, amplifier output, etc.).

* By ratio of the number of turns in the coils

:*'''Step-up'''

:: The secondary has more turns than the primary.

:*'''Step-down'''

:: The secondary has fewer turns than the primary.

:*'''Isolating'''

:: Intended to transform from one voltage to the same voltage. The two coils have approximately equal numbers of turns, although often there is a slight difference in the number of turns, in order to compensate for losses (otherwise the output voltage would be a little less than, rather than the same as, the input voltage).

:*'''Variable'''

:: The primary and secondary have an adjustable number of turns which can be selected without reconnecting the transformer.

In 1860 an abortive attempt at restoring the stone church was the cause of its additional disintegration, forcing the dome over the [[transept]] and its ''[[cupola]]'' (lantern house) to collapse. A [[smallpox]] [[epidemic]] swept through the area in 1862, nearly wiping out the remaining Juaneño Indians. [[Abraham Lincoln|President Abraham Lincoln]] signed a proclamation on [[March 18]], [[1865]] that returned ownership of the Mission proper to the [[Roman Catholic Church]]. The document remains on display in the Mission's barracks ''cum'' museum; it is one of the few documents he ever signed as "Abraham Lincoln" instead of his customary "A. Lincoln." The Mission's sole resident from 1866 to 1886 was its pastor, Father José Mut. Father Mut made certain changes in order to accommodate his own needs, but little was accomplished to prevent further deterioration of the Mission buildings. By 1891 a roof collapse required that the Serra Chapel be abandoned completely. Modifications were made to the original [[adobe]] church (including the addition of a cross-topped ''espadaña'' at the south end, a feature that has been retained in the present iteration of the Mission compound) in order to render it suitable for use as a [[parish]] church.

[[Image:Transformer_01.jpg|thumb|180px|right|Three phase dry-type transformer with cover removed; rated about 200 KVA, 480 V]]

In 1894, the [[Atchison, Topeka and Santa Fe Railway]] constructed a new depot in the emerging "[[Mission Revival Style architecture|Mission Revival Style]]" mere blocks from the Mission. It is rumored that the stonework, bricks, and roof tiles were salvaged from the decaying buildings.<ref>Duke, p. 241</ref> The following year, a group calling itself the '''Landmarks Club of Los Angeles''' made the first real efforts at preserving the Mission and restoring it to its original state in over fifty years. Over 400 tons of debris was cleared away, holes in the walls were patched, and new [[Shake (roof)|shake]] [[Thuja plicata|cedar]] roofs were placed over a few of the derelict buildings. A mile of walkways were repaved with asphalt and gravel as well.

===Losses===

===The 20th Century and beyond (1901 &ndash; present)===

An ideal transformer would have no losses, and would therefore be 100% efficient. In practice energy is dissipated due both to the [[electrical resistance|resistance]] of the windings (known as ''copper loss''), and to magnetic effects primarily attributable to the core (known as ''iron loss''). Transformers are in general highly efficient, and large power transformers (around 100 MVA and larger) may attain an efficiency as high as 99.75%. Small transformers such as a plug-in "power brick" used to power small consumer electronics may be less than 85% efficient.

[[Image:Historic American Buildings Survey Photographed by Henry F. Withey June 1936 VIEW OF SANCTUARY OF SERRA'S CHURCH colorized.jpg|thumb|250px|left|The "Golden Altar," an early [[Baroque]]-style ''retablo'' (altarpiece) situated at the north-end sanctuary of "Father Serra's Church."]]

After Father Mut's departure in 1886 the parish found itself without a permanent pastor, and the Mission languished during this period. Father St. John O'Sullivan arrived in San Juan Capistrano in 1910 to recuperate from a recent stroke, and to seek relief from chronic [[tuberculosis]].<ref>Wright, p. 39</ref> He became fascinated by the scope of the Mission and soon set to work on rebuilding it a section at a time. Father O'Sullivan's first task was to repair the roof of the Serra Chapel (which was being employed as a granary and storeroom) using [[sycamore]] logs to match those that were used in the original work; in the process, the roof of the [[apse]] was raised to allow for the inclusion of a window so that natural light could be brought into the space. Other refurbishments were made as time and funds permitted. Arthur B. Benton, a Los Angeles [[architect]], strengthened the chapel walls through the addition of heavy [[masonry]] [[buttress]]es.

The losses arise from:

It is rumored that [[silent film]] star [[Mary Pickford|Mary Pickford's]] secret marriage to fellow [[actor]] [[Owen Moore]] in 1911 took place in the Mission chapel. The third act of [[John Steven McGroarty|John Steven McGroarty's]] ''The Mission Play'' (1911) is set "''...amid the broken and deserted walls of Mission San Juan Capistrano (the Mission of the Swallow), in 1847''." Severe flooding destroyed a portion of the Mission's front arcade in 1915, and heavy storms a year later washed away one end of the barracks building, which Father O'Sullivan rebuilt in 1917, incorporating minor modifications such as an ornamental archway in order to make the edifice more closely resemble a church. In 1918 the Mission was given [[parochial]] status with Father O’Sullivan as its first modern pastor. It was on [[April 21]] of that year that the [http://www.data.scec.org/chrono_index/sanj1918.html San Jacinto Earthquake] caused moderate structural damage to some of the buildings. In 1919, author [[Johnston McCulley]] created the character "[[Zorro]]" and chose Mission San Juan Capistrano as the setting for the first novella, titled ''[[The Curse of Capistrano]]''.<ref>Yenne, P. 79</ref>

:* '''Winding resistance'''

:: Current flowing through the windings causes resistive heating of the conductors.

:* '''Eddy currents'''

:: Induced currents circulate in the core and cause its resistive heating.

:* '''Stray losses'''

:: Not all the magnetic field produced by the primary is intercepted by the secondary. A portion of the [[leakage flux]] may induce eddy currents within nearby conductive objects such as the transformer's support structure, and be converted to heat. The familiar hum or buzzing noise heard near transformers is a result of stray fields causing components of the tank to vibrate, and is also from magnetostriction vibration of the core.

:*'''Hysteresis losses'''

:: Each time the magnetic field is reversed, a small amount of energy is lost to [[hysteresis]] in the magnetic core. The level of hysteresis is affected by the core material.

:* '''Mechanical losses'''

:: The alternating magnetic field causes fluctuating electromagnetic forces between the coils of wire, the core and any nearby metalwork, causing vibrations and noise which consume power.

:* '''Magnetostriction'''

:: The flux in the core causes it to physically expand and contract slightly with the alternating magnetic field, an effect known as [[magnetostriction]]. This in turn causes losses due to frictional heating in susceptible [[ferromagnetic]] cores.

:* '''Cooling system'''

:: Large power transformers may be equipped with cooling fans, oil pumps or water-cooled heat exchangers designed to remove the heat caused by copper and iron losses. The power used to operate the cooling system is typically considered part of the losses of the transformer.

In 1920, the "Sacred Garden" was created in the courtyard adjacent to the stone church, and in 1925 the full restoration of the Serra Chapel was completed. Father O'Sullivan died in 1933 and was buried in the Mission [[cemetery]]. His tomb lies at the foot of a [[Celtic cross]] the Father himself erected as a [[memorial]] to the Mission's builders. In 1937 representatives of the U.S. [[National Park Service|National Park Service's]] [[Historic American Buildings Survey]], as a part of the [http://www.cr.nps.gov/local-law/FHPL_HistSites.pdf Historic Sites Act of 1935], surveyed and photographed the grounds and structures extensively. Their efforts laid the groundwork for future excavation and reconstruction of the west wing industrial complex.

===High frequency operation===

The universal transformer emf equation indicates that at higher frequency, the core flux density will be lower for a given voltage. This implies that a core can have a smaller cross-sectional area and thus be physically more compact without reaching [[Saturation (magnetic)|saturation]]. It is for this reason that the aircraft manufacturers and the military use 400 hertz supplies. They are less concerned with efficiency, which is lower at higher frequencies (mostly due to increased hysteresis losses), but are more concerned with saving weight. Similarly, [[flyback transformer]]s which supply high voltage to [[cathode ray tube]]s operate at the frequency of the horizontal oscillator, many times higher than 50 or 60 hertz, which allows for a more compact component.

The prestigious [[World Monuments Fund]] placed "The Great Stone Church" on its ''List of 100 Most Endangered Sites'' in 2002. The most recent series of [[seismic]] retrofits at the Mission were completed in 2004.

== Construction ==

<br style="clear:both;">

==Mission industries==

===Cores===

[[Image:Brand-mission san juan capistrano.png|thumb|300px|The cattle [[Livestock branding|brand]] used at Mission San Juan Capistrano.]]

==== Steel cores ====

The goal of the missions was, above all, to become self-sufficient in relatively short order. [[Farming]], therefore, was the most important [[industry]] of any mission. [[Barley]], [[maize]], and [[wheat]] were the principal crops grown at San Juan Capistrano; [[cattle]], [[horses]], [[mules]], [[sheep]], and [[goat]]s were all raised by the hundreds as well. In 1790 the Mission's herd included 7,000 sheep and goats, 2,500 cattle, and 200 mules and horses. [[Olive]]s were grown, cured, and pressed under large stone [[wheel]]s to extract their [[Vegetable oil|oil]], both for use at the Mission and to trade for other goods. [[Grapes]] were also grown and [[fermentation (food)|ferment]]ed into [[wine]] for [[sacramental]] use and again, for trading. The specific variety, called the ''Criolla'' or "[[Mission (grape)|Mission grape]]," was first planted at the Mission in 1779; in 1783, the first wine produced in Alta California emerged from San Juan Capistrano's winery. [[Cereal]] grains were dried and ground by stone into [[flour]]. The Mission's [[kitchen]]s and [[bakery|bakeries]] prepared and served thousands of meals each day. [[Candles]], [[soap]], [[Grease (lubricant)|grease]], and [[ointment]]s were all made from [[tallow]] ([[kitchen rendering|rendered]] [[animal]] [[fat]]) in large [[vat]]s located just outside the west wing. Also situated in this general area were vats for dyeing [[wool]] and [[tanning]] [[leather]], and primitive [[loom]]s for [[weaving]]s. Large ''bodegas'' (warehouses) provided long-term storage for preserved foodstuffs and other treated materials.

[[Image:Transformer.filament.agr.jpg|thumb|300px|Laminated core transformer showing edge of laminations at top of unit.]]

Transformers for use at power or audio frequencies have cores made of many thin laminations of [[silicon steel]]. By concentrating the magnetic flux, more of it is usefully linked by both primary and secondary windings. Since the steel core is conductive, it, too, has currents induced in it by the changing magnetic flux. Each layer is insulated from the adjacent layer to reduce the energy lost to [[eddy current]] heating of the core. A typical laminated core is made from E-shaped and I-shaped pieces, leading to the name "EI transformer".

[[Image:Mission San Juan Capistrano 4-5-05 100 6559.JPG|thumb|300px|right|A view of the [[Catalan forge]]s at Mission San Juan Capistrano, the oldest existing facilities (''circa'' 1790s) of their kind in the State of California. The sign at the lower right-hand corner proclaims the site as being "''...part of Orange County's first industrial complex.''"]]

Certain types of transformer may have gaps inserted in the magnetic path to prevent [[Saturation (magnetic)|magnetic saturation]]. These gaps may be used to limit the current on a short-circuit, such as for [[neon sign]] transformers.

Three long ''zanjas'' ([[aqueducts]]) ran through the central courtyard and deposited the water they collected into large [[cistern]]s in the industrial area, where it was filtered for drinking and cooking, or dispensed for use in cleaning. The Mission had to fabricate all of its construction materials as well. Workers in the ''carpintería'' ([[carpentry]] shop) used crude methods to shape beams, lintels, and other structural elements; more skilled artisans carved doors, furniture, and wooden implements. For certain applications bricks (''ladrillos'') were fired in [[oven]]s ([[kilns]]) to strengthen them and make them more resistant to the elements; when ''tejas'' (roof tiles) eventually replaced the conventional ''jacal'' roofing (densely-packed reeds) they were placed in the kilns to harden them as well. Glazed ceramic pots, dishes, and canisters were also made in the Mission's kilns.

A steel core's [[magnetic hysteresis]] means that it retains a static magnetic field when power is removed. When power is then reapplied, the residual field will cause a high [[inrush current]] until the effect of the remanent magnetism is reduced, usually after a few cycles of the applied alternating current. Overcurrent protection devices such as [[fuse (electrical)|fuses]] must be selected to allow this harmless inrush to pass. On transformers connected to long overhead power transmission lines, induced currents due to geomagnetic disturbances during solar storms can cause saturation of the core, and false operation of transformer [[relay|protection devices]].

Prior to the arrival of the missions, the native peoples knew only how to utilize bone, seashells, stone, and wood for building, tool making, weapons, and so forth. The [[foundry]] at Mission San Juan Capistrano was the first to introduce the Indians to the [[Iron Age]]. The [[blacksmith]] used the Mission’s [[Catalan forge|Catalan furnaces]] (California’s first) to [[smelt]] and fashion [[iron]] into everything from basic tools and hardware (such as [[nails]]) to crosses, gates, hinges, even [[cannon]] for Mission defense. Iron was one commodity in particular that the Mission relied solely on trade to acquire, as the missionaries had neither the know-how nor the technology to [[mining|mine]] and process [[metal]] [[ore]]s.

Distribution transformers can achieve low off-load losses by using cores made with amorphous (non-crystalline) steel, so-called "[[Amorphous#Metallic_glass|metal glasses]]" - the high cost of the core material is offset by the lower losses incurred at light load, over the life of the transformer.

====The SolidMission cores ==bells==

[[Image:Mission San Juan Capistrano 4-5-05 100 6548.JPG|thumb|300px|right|A view of Mission San Juan Capistrano's "Sacred Garden" that was developed in 1920. The four-bell ''campanario'' was erected a year after the bell tower at "The Great Stone Church" was toppled in the 1812 earthquake.]]

In circuits that operate above mains frequencies, up to a few tens of kilohertz, such as switch-mode power supplies, powdered iron cores are used. These materials combine a high magnetic [[permeability]] with a high bulk material resistivity. At even higher frequencies, typically radio frequencies, other types of core made of non-conductive magnetic materials, such as various [[ceramic]] materials called ''[[ferrite (magnet)|ferrites]]'', are common. Some transformers in [[radio]]-frequency circuits have adjustable cores which allow tuning of the coupling circuit.

Bells were vitally important to daily life at any mission. The bells were rung at mealtimes, to call the Mission residents to work and to religious services, during births and funerals, to signal the approach of a ship or returning missionary, and at other times. All four of Mission San Juan Capistrano's bells are named and all bear inscriptions as follows (from the largest to the smallest; inscriptions are translated from [[Latin]]):

==== Air cores ====

High-frequency transformers may also use air cores. These eliminate the loss due to [[hysteresis]] in the core material. Such transformers maintain high coupling efficiency (low stray field loss) by overlapping the primary and secondary windings.

* "''Praised by [[Jesus]], '''San Vicente'''. In honor of the Reverend Fathers, Ministers (of the Mission) Fray Vicente Fuster, and Fray Juan Santiago, 1796.''"

==== Toroidal cores ====

* "''Hail Mary most pure. Ruelas made me, and my name is '''San Juan''', 1796.''"

Toroidal transformers are built around a ring-shaped core, which is made from a long strip of silicon [[steel]] or [[permalloy]] wound into a coil, or from [[ferrite (magnet)|ferrite]], depending on frequency. The strip construction ensures that all the [[grain boundary|grain boundaries]] are pointing in the optimum direction, making the transformer more efficient by reducing the core's [[reluctance]]. The ring shape eliminates the air gaps inherent in the construction of an EI core. The cross-section of the ring is usually square or rectangular, but more expensive cores with circular cross-sections are also available. The primary and secondary coils are wound concentrically to cover the entire surface of the core. This minimises the length of wire needed, and also provides screening to prevent the core's magnetic field from generating [[electromagnetic interference]].

* "''Hail Mary most pure, '''San Antonio''', 1804.''"

* "''Hail Mary most pure, '''San Rafael''', 1804.''"

In the aftermath of the 1812 earthquake, the two largest bells cracked and split open. Due to this damage neither produced clear tones. Regardless, they were hung in the campanario that went up the following year.

Ferrite cores are used at frequencies up to a few tens of kilohertz to reduce losses, particularly in switch-mode power supplies.

On [[March 22]], [[1969]] [[Richard Nixon|President Richard M. Nixon]] and [[First Lady]] [[Patricia Nixon]] visited the Mission and rang the Bell of San Rafael. A bronze plaque commemorating the event is set in the bell wall. In celebration of the new Mission church being elevated to minor basilica status in 2000, exact duplicates of the damaged bells were cast in the [[Netherlands]], utilizing molds made from the originals. The replacement bells were placed in the bell wall and the old ones put on display within the footprint of the destroyed Mission ''campanile'' ("bell tower").

Toroidal transformers are more efficient (around 95%) than the cheaper laminated EI types. Other advantages, compared to EI types, include smaller size (about half), lower weight (about half), less mechanical hum (making them superior in audio amplifiers), lower exterior magnetic field (about one tenth), low off-load losses (making them more efficient in standby circuits), single-bolt mounting, and more choice of shapes. This last point means that, for a given power output, either a wide, flat [[toroid]] or a tall, narrow one with the same electrical properties can be chosen, depending on the space available. The main disadvantage is higher cost.

=="The return of the swallows"==

A drawback of toroidal transformer construction is the higher cost of windings. As a consequence, toroidal transformers are uncommon above ratings of a few kVA. Small distribution transformers may achieve some of the benefits of a toroidal core by splitting it and forcing it open, then inserting a bobbin containg primary and secondary windings.

[[Image:Mission San Juan Capistrano 4-5-05 100 6552.JPG|thumb|250px|left|Looking down the [[Arcade (architecture)|arcade]] at Mission San Juan Capistrano's old adobe chapel. Cliff Swallows, annual visitors to the Mission, typically build their nests here. Note that much of the [[plaster]] finish has come off, exposing the [[brick]]s beneath to the elements.]]

The [[Cliff Swallow]] (''Petrochelidon pyrrhonota'') is a [[migratory]] bird that spends its winters in [[Goya, Corrientes|Goya]], [[Argentina]] but makes the 6,000-mile trek north to the warmer climes of the [[American Southwest]] in springtime. According to legend the birds, who have visited the San Juan Capistrano area every Summer for centuries, first took refuge at the Mission when an irate innkeeper began destroying their mud nests. The Mission's ___location near two [[river]]s made it an ideal ___location for the swallows to nest, as there was a constant supply of the [[insect]]s on which they feed, and the young birds are well-protected inside the ruins of the old stone church.

When fitting a toroidal transformer, it is important to avoid making an unintentional [[short-circuit]] through the core. This can happen if the steel mounting bolt in the middle of the core is allowed to touch metalwork at both ends, which could result in a dangerously large current flowing in the bolt.

Father O'Sullivan made note of the birds' annual habit of nesting beneath the Mission's eaves and archways, from Spring through Fall, during his two decades in residence. On [[March 13]], [[1939]] a popular radio program was broadcast live from the Mission grounds, announcing the swallows' return. Composer [[Leon René]] was so inspired by the event that he penned the song ''When the Swallows Come Back to Capistrano'' in tribute.<ref>Leffingwell, p. 39</ref> During its initial release the song spent several weeks atop the ''[[Your Hit Parade]]'' charts. The song has been recorded by such musicians as [[The Ink Spots]], [[Fred Waring]], [[Guy Lombardo]], and [[Glenn Miller]]. A glassed-off room in the Mission has been designated in René's honor and displays the upright piano on which he composed the tune, the reception desk from his office and several copies of the song's sheet music and other pieces of furniture, all donated by René's family.

=== Windings ===

In most practical transformers, the primary and secondary conductors are coils of conducting [[wire]] because each turn of the coil contributes to the [[magnetic field]], creating a higher [[magnetic flux density]] than would a single conductor.

Each year the City of San Juan Capistrano sponsors the ''Fiesta de las Golondrinas'', a week-long celebration of this auspicious event. Tradition has it that the main [[flock]] arrives on [[March 19]] (''[[Saint Joseph|Saint Joseph's Day]]''), and flies south on ''[[Giovanni da Capistrano|Saint John's Day]]'', [[October 23]].

The winding material depends on the application. Small power and signal transformers are wound with insulated solid copper wire, often [[Enameled wire|enameled]]. Larger power transformers may be wound with wire, copper or aluminum rectangular conductors, or strip conductors for very heavy currents. High frequency transformers operating in the tens to hundreds of kilohertz will have windings made of [[Skin effect#Mitigation|Litz wire]], to minimize the skin effect losses in the conductors. Large power transformers use multiply-stranded conductors as well, since even at low power frequencies non-uniform distribution of current would otherwise exist in large windings. Each strand is insulated from the others, and the strands are arranged so that either at certain points in the winding or throughout the winding, each portion occupies different relative positions in the complete conductor. This "transposition" equalises the current flowing in each strand of the conductor, and reduces [[eddy current]] losses in the winding itself. The stranded conductor is also more flexible than a solid conductor of similar size. ( see reference (1) below)

<br>

Windings on both primary and secondary of a power transformer may have external connections (called taps) to intermediate points on the winding to allow adjustment of the voltage ratio; taps may be connected to automatic on-load [[tap changer]] [[switchgear]] for [[Voltage regulator|voltage regulation]] of [[Power distribution|distribution]] circuits. Audio-frequency transformers used for distribution of audio to public address loudspeakers have taps to allow adjustment of power supplied to each speaker. A center-tapped transformer is often used in the output stage of an audio power [[amplifier]] in a [[push-pull]] circuit. Tapped transformers are also used as components of amplifiers, oscillators, and for [[feedback]] linearization of amplifier circuits.

::::::::::::'''''When the swallows come back to Capistrano'''''

=== Insulation ===

::::::::::::'''''That's the day you promised to come back to me'''''

The conductor material must have insulation to ensure the current travels around the core, and not through a turn-to-turn short-circuit.

::::::::::::'''''When you whispered, "Farewell," in Capistrano'''''

::::::::::::''''''twas the day the swallows flew out to sea'''''

:::::::::::::<small>excerpt from "When the Swallows Come Back to Capistrano" by Leon René</small>

In power transformers, the voltage difference between parts of the primary and secondary windings can be quite large. Insulation is inserted between layers of windings to prevent arcing, and the transformer may also be immersed in [[transformer oil]] that provides further insulation. To ensure that the insulating capability of the transformer oil does not deteriorate, the transformer casing is completely sealed against moisture ingress. The oil serves as both cooling medium to remove heat from the core and coil and as part of the insulation system.

==Other historic designations==

=== Shielding ===

* [[California Historical Landmark]] [http://ohp.parks.ca.gov/default.asp?page_id=21445 #227] &mdash; Diego Sepúlveda Adobe ''Estancia''

Although an ideal transformer is purely magnetic in operation, the proximity of the primary and secondary windings can create a mutual capacitance between the windings. Where transformers are intended for high electrical isolation between primary and secondary circuits, an electrostatic shield can be placed between windings to minimize this effect.

* [http://www.asminternational.org/Content/NavigationMenu/Membership/AwardsProgram/HistoricalLandmarks/Landmarks.htm ASM International Historical Landmark] (1988) &mdash; "Metalworking Furnaces"

* [http://wmf.org/html/programs/ussanj.html World Monuments Fund ''List of 100 Most Endangered Sites''] (2002) &mdash; "The Great Stone Church"

==Notes==

Transformers may also be enclosed by magnetic shields, electrostatic shields, or both to prevent outside interference from affecting the operation of the transformer, or to prevent the transformer from affecting the operation of other devices (such as [[Cathode ray tube|CRTs]] in proximity to the transformer).

[[Image:San Juan Capistrano circa 1910 William Amos Haines.jpg|thumb|300px|right|An overall view of "The Mission of the Swallow" around the time of Father St. John O'Sullivan's arrival in 1910.]]

[[Image:Fray Engelhardt SJC 1915.jpg|thumb|300px|right|Clerical historian Father [[Zephyrin Engelhardt]], O.F.M. visits Mission San Juan Capistrano in 1915.]]

=== Coolant ===

All transformers must have some circulation of [[coolant]] to remove the waste heat produced by losses. Small transformers up to a few kilowatts in size usually are adequately cooled by air circulation. Larger "dry" type transformers may have cooling fans. Some dry transformers are enclosed in pressurized tanks and are cooled by [[nitrogen]] or [[sulfur hexafluoride]] gas.

<references/>

The windings of high-power or high-voltage transformers are immersed in [[transformer oil]] - a highly-refined [[mineral oil]] that is stable at high temperatures. Large transformers to be used indoors must use a non-flammable liquid. Formerly, [[polychlorinated biphenyl]] (PCB) was used as it was not a fire hazard in indoor power transformers and it is highly stable. Due to the stability of PCB and its environmental accumulation, it is no longer permitted in new equipment. Today, nontoxic, stable [[silicone]]-based oils or [[fluorocarbon|fluorinated hydrocarbon]]s may be used, where the expense of a fire-resistant liquid offsets additional building cost for a transformer vault. Other less-flammable fluids such as [[canola oil]] may be used but all fire resistant fluids have some drawbacks in performance, cost, or toxicity compared with mineral oil.

==References==

The oil cools the transformer, and provides part of the electrical insulation between internal live parts. It has to be stable at high temperatures so that a small short or arc will not cause a breakdown or fire. The oil-filled tank may have radiators through which the oil circulates by natural convection. Very large or high-power transformers (with capacities of millions of [[watt]]s) may have cooling fans, oil pumps and even oil to water [[heat exchangers]]. Oil-filled transformers undergo prolonged drying processes, using vapor-phase heat transfer, electrical self-heating, the application of a [[vacuum]], or combinations of these, to ensure that the transformer is completely free of [[water vapor]] before the cooling oil is introduced. This helps prevent electrical breakdown under load.

[[Image:MSJC_by_John_Gutzon-Borglum.jpg|thumb|300px|An 1894 painting by [[Fred Behre]] and [[Gutzon Borglum|John Gutzon Borglum]] depicts the intact Mission. Watercolor and gouache.]]

* {{cite book|author=Camphouse, Marjorie|year=1974|title=Guidebook to the Missions of California|publisher=Anderson, Ritchie & Simon, Los Angeles, CA|id=ISBN 0-378-03792-7}}

Oil-filled power transformers may be equipped with [[Buchholz relay]]s - safety devices sensing gas buildup inside the transformer (a side effect of an [[electric arc]] inside the windings) and switching off the transformer.

* {{cite book|author=Cathers, David M.|year=1981|title=Furniture of the American Arts and Crafts Movement|publisher=The New American Library, Inc|id=ISBN 0453003974}}

* Chase, J. and Saunders, C. (1974). "Mission San Juan Capistrano." ''American West'' '''40''' (7) 22-29.

Experimental power transformers in the 2 MVA range have been built with [[superconductivity|superconducting]] windings which eliminates the copper losses, but not the core steel loss. These are cooled by liquid [[nitrogen]] or [[helium]].

* {{cite book|author=Duke, Donald|year=1995|title=Santa Fe: The Railroad Gateway to the American West, Volume One|publisher=Golden West Books, San Marino, CA|id=ISBN 0-87095-110-6}}

* {{cite book|author=Engelhardt, Zephyrin|year=1922|title=San Juan Capistrano Mission|publisher=Standard Printing Co., Los Angeles, CA|id=}}

===Terminals===

* {{cite book|author=Kelsey, H.|year=1993|title=Mission San Juan Capistrano: A Pocket History|publisher=Interdisciplinary Research, Inc., Altadena, CA|id=}}

Very small transformers will have wire leads connected directly to the ends of the coils, and brought out to the base of the unit for circuit connections. Larger transformers may have heavy bolted terminals, bus bars or high-voltage insulated [[Bushing (electrical)|bushings]] made of polymers or porcelain. A large bushing can be a complex structure since it must both provide electrical insulation, and contain oil within the transformer tank.

* {{cite book|author=Jones, Roger W.|year=1997|title=California from the Conquistadores to the Legends of Laguna|publisher=Rockledge Enterprises, Laguna Hills, CA|id=}}

* {{cite book|author=Leffingwell, Randy|year=2005|title=California Missions and Presidios: The History & Beauty of the Spanish Missions|publisher=Voyageur Press, Inc., Stillwater, MN|id=ISBN 0-89658-492-5}}

===Enclosure===

* {{cite book|author=Newcomb, Rexford|year=1973|title=The Franciscan Mission Architecture of Alta California|publisher=Dover Publications, Inc., New York, NY|id=ISBN 0-486-21740-X}}

Small transformers often have no enclosure. Transformers may have a shield enclosure, as described above. Larger units may be enclosed to prevent contact with live parts, and to contain the cooling medium (oil or pressurized gas).

* {{cite book|author=Ruscin, Terry|year=1999|title=Mission Memoirs|publisher=Sunbelt Publications, San Diego, CA|id=ISBN 0-932653-30-8}}

* {{cite book|author=Wright, Ralph B.|year=1950|title=California's Missions|publisher=Hubert A. and Martha H. Lowman, Arroyo Grande, CA|id=}}

== Transformer designs ==

* {{cite book|author=Yenne, Bill|year=2004|title=The Missions of California|publisher=Thunder Bay Press, San Diego, CA|id=ISBN 1-59223-319-8}}

* {{cite book|author=Young, Stanley and Melba Levick|year=1988|title=The Missions of California|publisher=Chronicle Books LLC, San Francisco, CA|id=ISBN 0-8118-3694-0}}

=== Autotransformers ===

* {{cite web|title=Mission San Juan Capistrano|work=San Juan Capistrano Historical Society|url=http://www.sjchistoricalsociety.com/missionsjc.html|accessdate=March 29|accessyear=2006}}

{{main|Autotransformer}}

An [[autotransformer]] has only a single winding, which is tapped at some point along the winding. AC or pulsed voltage is applied across a portion of the winding, and a higher (or lower) voltage is produced across another portion of the same winding. For voltage ratios not exceeding about 3:1, an autotransformer is less costly, lighter, smaller and more efficient than a two-winding transformer of a similar rating.

By exposing part of the winding coils and making the secondary connection through a sliding [[brush (electric) | brush]], an autotransformer with a near-continuously variable turns ratio can be obtained, allowing for very small increments of voltage.

=== Polyphase transformers ===

[[Image:Wye_Delta_01.png|300px|thumb|right|Wye and delta winding connections]]

For [[Three-phase electric power|three-phase power]], three separate single-phase transformers can be used, or all three phases can be connected to a single polyphase transformer. The three primary windings are connected together and the three secondary windings are connected together. The most common connections are Y-Δ, Δ-Y, Δ-Δ and Y-Y. A [[vector group]] indicates the configuration of the windings and the [[phase angle]] difference between them. If a winding is connected to earth (grounded), the earth connection point is usually the center point of a Y winding. There are many possible configurations that may involve more or fewer than six windings and various tap connections.

=== Resonant transformers ===

A [[resonance|resonant]] transformer is one that operates at the [[resonant frequency]] of one or more of its coils. The resonant coil, usually the secondary, acts as an [[inductor]], and is connected in series with a [[capacitor]]. If the primary coil is driven by a periodic source of [[alternating current]], such as a square or sawtooth wave, each pulse of current helps to build up an oscillation in the secondary coil. Due to resonance, a very high voltage can develop across the secondary, until it is limited by some process such as [[electrical breakdown]]. These devices are therefore used to generate high alternating voltages. The current available from this type of coil can be much larger than that from electrostatic machines such as the [[Van de Graaff generator]] and [[Wimshurst machine]]. They also run at a higher operating temperature than standard units.

Examples:-

*[[Tesla coil]]

*[[Oudin coil]] (or Oudin resonator; named after its inventor [[Paul Oudin]])

*[[Jacques Arsene d'Arsonval|D'Arsonval]] apparatus

*[[ignition coil]] or [[induction coil]] used in the [[ignition system]] of a [[petrol engine]]

*[[Flyback transformer]] of a [[CRT]] [[television]] set or video monitor.

Other applications of resonant transformers are as coupling between stages of a [[superheterodyne receiver]], where the selectivity of the receiver is provided by the tuned transformers of the intermediate-frequency amplifiers.

A voltage regulating transformer uses a resonant winding and allows part of the core to go into saturation on each cycle of the alternating current. This effect stabilizes the output of the regulating transformer, which can be used for equipment that is sensitive to variations of the supply voltage. Saturating transformers provide a simple rugged method to stabilize an ac power supply. However, due to the hysteresis losses accompanying this type of operation, efficiency is low.

===Instrument transformers===

====Current transformers====

[[Image:CurrentTransformers.jpg|right|thumb|300px|Current transformers used as part of [[electricity meter|metering equipment]] for [[three-phase]] 400 ampere electricity supply]]A '''current transformer''' is designed to provide a current in its secondary which is accurately proportional to the current flowing in its primary.

Current transformers are commonly used in [[electricity meter]]s to facilitate the measurement of large currents which would be difficult to measure more directly.

Care must be taken that the secondary of a current transformer is not disconnected from its load while current is flowing in the primary as in this circumstance a very high voltage would be produced across the secondary.

Current transformers are often constructed with a single primary turn either as an insulated cable passing through a toroidal core, or else as a bar to which circuit conductors are connected.

====Voltage transformers====

Voltage transformers (also known as potential transformers) are used in the electricity supply industry to measure accurately the voltage being supplied. They are designed to present negligible load to the voltage being measured.

=== Pulse transformers ===

A '''pulse transformer''' is a transformer that is optimised for transmitting rectangular electrical pulses (that is, pulses with fast rise and fall times and a constant [[amplitude]]). Small versions called ''signal'' types are used in [[digital logic]] and [[telecommunications]] circuits, often for matching logic drivers to [[transmission line]]s. Medium-sized ''power'' versions are used in power-control circuits such as [[camera flash]] controllers. Larger ''power'' versions are used in the [[electrical power distribution]] industry to interface low-voltage control circuitry to the high-voltage gates of [[Power semiconductor device|power semiconductor]]s such as [[TRIAC]]s, [[IGBT]]s, [[thyristor]]s and [[MOSFET]]s. Special [[high voltage]] pulse transformers are also used to generate high power pulses for [[radar]], [[particle accelerators]], or other [[pulsed power]] applications.

To minimise distortion of the pulse shape, a pulse transformer needs to have low values of leakage inductance and distributed capacitance, and a high open-circuit inductance. In power-type pulse transformers, a low coupling capacitance (between the primary and secondary) is important to protect the circuitry on the primary side from high-powered transients created by the load. For the same reason, high insulation resistance and high breakdown voltage are required. A good transient response is necessary to maintain the rectangular pulse shape at the secondary, because a pulse with slow edges would create switching losses in the power semiconductors.

The product of the peak pulse voltage and the duration of the pulse (or more accurately, the voltage-time integral) is often used to characterise pulse transformers. Generally speaking, the larger this product, the larger and more expensive the transformer.

===RF transformers ===

For [[radio frequency]] use, transformers are sometimes made from configurations of transmission line, sometimes [[bifilar]] or [[coaxial]] cable, wound around [[ferrite]] cores. This style of transformer gives an extremely wide [[bandwidth]], however only a limited number of ratios (such as 1:9, 1:4 or 1:2) can be achieved with this technique. The ferrite increases the inductance dramatically while also lowering its [[Q factor]]. The cores of such transformers help performance at the lower frequency end of the band. This style of transformer is frequently used as an [[impedance matching]] [[balun]] to convert from 300 ohm balanced to 75 ohm unbalanced in FM receivers.

== Audio transformers ==

Traditionally, in the [[valve amplifier]], the function of the output transformer was to convert the low [[alternating current]] music signal (that had been imposed on top of the high-voltage [[direct current]] from the [[plate electrode]] of the final output tube) into a useable high-current/low-voltage level for conversion by the [[loudspeakers]].

The exception to this use was the [[valve amplifier]] designed by [[Julius Futterman]] that allowed for a direct connection of the [[vacuum tube]] output.

In early [[transistor]] amplifiers, such transformers were also used.

== Uses of transformers ==

* [[Electric power transmission]] over long distances.

* High-voltage direct-current [[HVDC]] power transmission systems

* Large, specially constructed power transformers are used for [[electric arc furnace]]s used in [[steelmaking]].

* Rotating transformers are designed so that one winding turns while the other remains stationary. A common use was the video head system as used in VHS and Beta video tape players. These can pass power or radio signals from a stationary mounting to a rotating mechanism, or [[radar]] [[antenna (electronics)|antenna]].

* Sliding transformers can pass power or signals from a stationary mounting to a moving part such as a machine tool head. See [[linear variable differential transformer]],

* Some rotary transformers are precisely constructed in order to measure distances or angles. Usually they have a single primary and two or more secondaries, and electronic circuits measure the different amplitudes of the currents in the secondaries. See [[synchro]] and [[Resolver (electrical)|resolver]].

* Small transformers are often used to isolate and link different parts of [[radio receiver]]s and [[audio amplifier]]s, converting high current low voltage circuits to low current high voltage, or vice versa. See [[electronics]] and [[impedance matching]]. See also [[isolation transformer]] and [[repeating coil]].

* Balanced-to-unbalanced conversion. A special type of transformer called a [[balun]] is used in radio and audio circuits to convert between balanced circuits and unbalanced [[transmission line]]s such as antenna downleads. A [[balanced line]] is one in which the two conductors (signal and return) have the same [[impedance]] to ground: twisted pair and "balanced twin" are examples. [[Unbalanced line]]s include [[coaxial cable]]s and strip-line traces on [[printed circuit board]]s. A similar use is for connecting the "single ended" input stages of an amplifier to the high-powered "push-pull" output stage.

==See also==

* [[Spanish missions in California]]

{{wikibookspar||School science/How to make a transformer}}

* [[Diego Sepúlveda Adobe]]

* [[Las Flores Asistencia]]

* ''Main'' : [[Distributed generation]], [[Electronic power supply]], [[Electronics]], [[Inductor]], [[Pickup]], [[Electrical network]], [[Electricity distribution]], [[Wet transformer]], [[List of electronics topics]], [[Electronic Transformers]]

* [[USNS Mission Capistrano (AO-112)|USNS ''Mission Capistrano'' (AO-112)]] &mdash; a [[USNS Mission Buenaventura (AO‑111)|''Mission Buenaventura'']] Class [[Oiler (ship)|fleet oiler]] built during [[World War II]].

* ''Circuits'': [[Clamp meter]], [[Repeating coil]], [[Inverter (electrical)]], [[Ignition system]], [[Electricity generation]], [[Linear variable differential transformer]], [[Neon signage]], [[Regulator]], [[Electrical substation]], [[Switched-mode power supply]], [[Technological applications of superconductivity]], [[Tesla coil]], [[Transducer]]

* ''Electromagnetism'': [[Alternating current]], [[Electric power]], [[Electric power transmission]], [[Electromagnetic induction]], [[Equivalent series resistance]], [[High-voltage direct current]], [[Impedance matching]], [[Inductive coupling]], [[Potential difference]], [[Skin effect]], [[Leakage inductance]], [[Superconductivity]]

* ''People'': [[Ottó Bláthy]], [[Miksa Déri]], [[John Ambrose Fleming]], [[Otto A. Knopp]], [[William Stanley (physicist)|William Stanley]], [[Nikola Tesla]], [[Milan Vidmar]], [[George Westinghouse]], [[Károly Zipernowsky]]

* ''Other'': [[DI unit]], [[Polychlorinated biphenyl]], [[Stafford]], [[Timeline of invention]], [[War of Currents]], [[World's Columbian Exposition]]

== External links ==

*[http://www.du.edu/~jcalvert/tech/transfor.htm ''Inside Transformers'' from Denver University]

== References ==

* (1) {{Book reference | Author=Central Electricity Generating Board | Title=Modern Power Station Practice |Publisher=Pergamon | Year=1982 | ID=ISBN 0-08-016436-6}}

* {{Book reference | Author=Daniels, A.R. | Title=Introduction to Electrical Machines|Publisher=Macmillan | Year=1985 | ID=ISBN 0-333-19627-9}}

* {{Book reference | Author=Heathcote, MJ | Title=J&P Transformer Book, 12th ed. | Publisher=Newnes| Year=1998 | ID=ISBN 0-7506-1158-8}}

* {{Book reference | Author=Hindmarsh, J. | Title=Electrical Machines and their Applications, 4th ed. | Publisher=Pergamon | Year=1984 | ID=ISBN 0-08-030572-5}}

* {{Book reference | Author=Shepherd,J; Moreton,A.H; Spence,L.F. | Title=Higher Electrical Engineering | Publisher=Pitman Publishing| Year=1970 | ID=ISBN 0-273-40025-8}}

*[http://www.gass-transformatoren.de/en/frame_wissenswert.htm Kinds of Transformers]

==External links==

[[Category:Electronics]]

[[Image:Basilica San Juan Capistrano 1987.jpg|thumb|300px|right|The Basilica at San Juan Capistrano, designed after the "Great Stone Church," in 1987.]]

[[Category:Transformers (electrical)|*]]

* [http://www.missionparish.org/ Official parish website]

* [http://www.mymission.org/images/juancap.gif Elevation & Site Layout sketches of the Mission proper]

* [http://memory.loc.gov/cgi-bin/ampage?collId=hhdatapage&fileName=ca/ca0400/ca0449/data/hhdatapage.db&recNum=0&itemLink=D?hh:73:./temp/~ammem_y9wL:: Historic American Buildings Survey/Historic American Engineering Record]

* [http://virtualguidebooks.com/SouthCalif/LosAngeles/Capistrano/CapistranoStoneChurch.html Virtual Reality Panorama of "The Ruined Stone Church"]

* [http://virtualguidebooks.com/SouthCalif/LosAngeles/Capistrano/CapistranoColonnade.html Virtual Reality Panorama of the "Cloister Colonnade at Mission San Juan Capistrano"]

* [http://virtualguidebooks.com/SouthCalif/LosAngeles/Capistrano/CapistranoCourtyard.html Virtual Reality Panorama of "The Inner Courtyard"]

* [http://virtualguidebooks.com/SouthCalif/LosAngeles/Capistrano/CapistranoSerraChapel.html Virtual Reality Panorama of "Father Serra's Chapel"]

* [http://www.missionsjc.com/pdf/edu/DailyLife.pdf Daily Life at Mission San Juan Capistrano] ([[PDF]])

* [http://www.missionsjc.com/pdf/edu/MissionIndians.pdf Indians of the Mission] ([[PDF]])

* [http://www.octhen.com/Landmarks/Mission/lca/index.htm "Little Chapters about San Juan Capistrano" by Father St. John O'Sullivan, 1912]

* [http://www.webroots.org/library/usahist/ca/cahaoto0.html "Chinigchinich; a Historical Account of the Origin, Customs, and Traditions of the Indians at the Missionary Establishment of St. Juan Capistrano, Alta California Called The Acagchemem Nation" by The Reverend Father Friar Gerónimo Boscana, 1846]

* [http://www.juaneno.com/ Official website of the Juaneño Band of Mission Indians, Acjachemem Nation]

{|

[[Image:CHS.J3074.jpg|thumb|300px|left|One of the earliest examples of "Mission Revival Style" architecture, the Sante Fe Railway depot in San Juan Capistrano (with its 40-foot high dome and bell) was considered to be one of the railroad's finest when it was completed on October 8, 1894.]]

|

[[Image:Mission San Juan Capistrano circa 1921.jpg|thumb|300px|right|This ''circa'' 1921 view of the Mission San Juan Capistrano complex documents the restoration work that was already well underway by that time. The perimeter garden wall, including the ornate entranceway, is an early-20th century addition.]]

|}

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