Villanova Wildcats - wikipedia Villanova Wildcats Jump to : navigation , search Villanova Wildcats University Villanova University Conference Big East Conference CAA ( football & women 's rowing ) NCAA Division I / FCS Athletic director Mark Jackson Location Villanova , Pennsylvania Varsity teams 24 Football stadium Villanova Stadium Basketball arena William B. Finneran Pavilion ( on campus ) Wells Fargo Center ( high - attendance games ) Baseball stadium Villanova Ballpark at Plymouth Soccer stadium Higgins Soccer Complex Mascot Will D. Cat Nickname Wildcats Fight song `` V for Villanova '' Colors Navy Blue and White Website www.villanova.com The Villanova Wildcats are the athletic teams of Villanova University . They compete in the Big East ( NCAA Division I ) for every sport except football and women 's rowing , where they compete in the Colonial Athletic Association ( Football Championship Subdivision , formerly Division I - AA , for football only ) . On December 15 , 2012 , Villanova and the other six Catholic , non-FBS schools announced that they were departing the Big East for a new conference . This conference assumed the Big East name on July 1 , 2013 . Contents ( hide ) 1 Teams 1.1 Men 's basketball 1.2 Women 's basketball 1.3 Football 1.4 Men 's lacrosse 1.5 Track and field 1.6 Cross country 1.7 Swimming and diving 2 NCAA team championships 3 Conference realignment 4 Notable non varsity sports 4.1 Rugby 5 See also 6 References 7 External links Teams ( edit ) Men 's sports Women 's sports Baseball Basketball Basketball Cross country Cross country Field hockey Football Lacrosse Golf Rowing Lacrosse Soccer Soccer Softball Swimming & diving Swimming & diving Tennis Tennis Track & field Track & field Volleyball Waterpolo † -- Track and field includes both indoor and outdoor . Men 's Basketball ( edit ) Main article : Villanova Wildcats men 's basketball The Villanova Wildcats compete in the Big East Conference and are coached by Jay Wright . The team has traditionally divides its home schedule between its on - campus arena , the William B. Finneran Pavilion , and the Wells Fargo Center in South Philadelphia , for larger draws . During the 2017 - 18 season , the team played its entire home schedule that season at the Wells Fargo Center following the reconstruction of the Pavilion scheduled to be completed in time for the 2018 - 19 school year . Wright has taken the Wildcats to 12 postseason appearances including 7 consecutive trips ( 2005 -- 2011 ) and 5 consecutive trips ( 2013 - 2017 ) to the NCAA Tournament . The 2011 - 12 team struggled and missed postseason but Coach Wright brought a surprising young team back to the 2013 NCAA Tournament . Villanova has appeared in the NIT 17 times , winning in 1994 , and won the Big East Tournament in 1995 , 2015 and 2017 . The Wildcats have appeared in the NCAA Men 's Tournament 37 times , the 8th highest total in NCAA history have reached the Elite Eight 13 times . They have been to the Final Four of the NCAA Division I Men 's Basketball Tournament on five occasions . The 1939 team coached by Al Severance reached the inaugural NCAA Final Four played at the Palestra for the 1939 NCAA Basketball Tournament . All - American Howard Porter led a Wildcat team coached by Jack Kraft to Final Four of the 1971 NCAA University Division Basketball Tournament . Coach Rollie Massimino took Villanova to a surprising 1985 National Championship . Current Coach Jay Wright reached the Final Four at the 2009 NCAA Division I Men 's Basketball Tournament behind Dante Cunningham and Scottie Reynolds . The team most recently won the 2018 NCAA Division I Men 's Basketball Tournament for their third National Championship . Villanova won the 1985 NCAA Division I Men 's Basketball Tournament with a historic 66 - 64 win over top - seeded Georgetown . The eighth - seeded Wildcats ( unranked in the final AP poll ) beat Dayton ( at Dayton ) , top - seeded Michigan , Maryland and second - seeded North Carolina to win the Southeast Regional en route to the Final Four in Lexington , Kentucky . After defeating 2 - seed Memphis State ( now known as Memphis ) in the national semifinals , Villanova met defending champion and ten - point - favorite Georgetown , led by Patrick Ewing , in the title game on April 1 , 1985 . The Wildcat squad remains the lowest overall seed in tournament history to win the championship , and their overall team shooting percentage of 78.6 % remains an NCAA tournament record for a single game . This Championship Game is often cited among the greatest upsets in college basketball history . Ed Pinckney , who shot 5 - of - 7 and had 16 points in the game , was named the NCAA Tournament 's Most Outstanding Player . On April 4 , 2016 , the Wildcats won their second NCAA Championship in Men 's Basketball , the first time in 31 years . They beat the North Carolina Tar Heels 77 - 74 off a buzzer - beater shot by Kris Jenkins with 0.5 seconds remaining in regulation . Two years later , on April 2 , 2018 , Villanova earned its third national championship beating the Michigan Wolverines 79 - 62 . Women 's Basketball ( edit ) Main article : Villanova Wildcats women 's basketball 600th win The Villanova Wildcats women 's basketball team are coached by Harry Perretta , now serving his 34th year as head coach of the team . For the 2017 -- 18 season , they will play their home games at Jake Nevin Field House on the Villanova campus while the future Finneran Pavilion is undergoing renovations . The Women 's basketball program started in 1969 and played under CIAW and AIAW through 1981 - 82 season before moving to NCAA Division I. In the 81 - 82 season , the Wildcats posted an outstanding 29 - 4 record and reached the Final Four of the 1982 AIAW Women 's Basketball Tournament before losing to eventual National Champion , Rutgers . Through the 2009 - 10 season , the Villanova Women have a 669 - 413 alltime record since the program started in 1969 . Previous head coaches include Liz Cawley ( 1969 -- 70 ) , Jane Sefranek - Stoltz ( 1970 -- 75 ) and Joan King ( 1975 -- 78 ) . The 1982 - 83 season was the initial season for Villanova Women 's basketball to play NCAA Division I and they joined the Big East Conference that same season . Villanova was the Big East regular season and tournament champions in both 1985 - 86 and 1986 - 87 behind All - American Shelly Pennefather . During the 2008 - 09 season , Coach Perretta led the Wildcats to the NCAA Tournament for the ninth time in his Villanova career . This marked the ninth postseason appearance in the previous 10 years for the Wildcats . After playing in the 2000 WNIT , Villanova went to four consecutive NCAA Tournaments from 2001 to 2004 before playing in the WNIT in 2005 , 2006 and 2008 . The 2002 - 03 season was a special one for the Wildcats . In addition to an impressive 28 - 6 overall record and a 12 - 4 Big East Conference mark , the Wildcats won their third Big East Conference Tournament championship and first since 1987 with an improbable 52 - 48 upset over previously unbeaten Connecticut . The win snapped Connecticut 's then NCAA Division I women 's basketball record of 70 - straight victories and ended Connecticut 's streak of nine - straight conference tournament championships . The dean of the Big East and Big 5 coaches , Harry Perretta has brought the Wildcats national respect and success during his tenure at Villanova which began in 1978 at the age of 22 . Coach Perretta reached a coaching milestone on November 12 , 2011 with a win over Iona , representing the 600th win of his career . He is the 35th coach in the history of women 's basketball at any level to reach the 600 win plateau , including the 22nd to accomplish the feat at the Division I level . Perretta is only the seventh NCAA Division I coaches to have 600 victories all at one school . On February 8 , 2012 , Perretta reached another milestone as he became the seventh coach across all NCAA divisions to coach 1,000 games at the same institution . Perretta was named the 2009 Big East Conference Co-Coach of the Year . That was the third time in his career that he has garnered Big East Coach of the Year distinction . He has led the Wildcats to fourteen seasons of 20 wins or more . Since joining the Big East in 1982 , Perretta has compiled a 200 - 175 conference record through 2010 . Shelly Pennefather , was recognized in 1987 as the nation 's top women 's college basketball player , winning the Margaret Wade Trophy and earning Kodak All - America honors . Pennefather was the first 3 - time winner of the Big East Conference Women 's Basketball Player of the Year . She is the all - time leading scorer in the history of Villanova basketball with 2408 points . Pennefather was named the best Colorado Girls High school player of all - time and led Bishop Machebeuf Catholic High School to a 96 - 0 record and 3 State Championships . Football ( edit ) Main article : Villanova Wildcats football The Wildcats compete in the Colonial Athletic Association and are coached by Andy Talley who is the winningest football coach in school history with a 190 - 117 - 1 (. 617 ) record . Since moving to I - AA , Villanova has made 9 appearances in the I - AA / FCS playoffs making trips to the NCAA Semifinal in 2002 and 2010 and winning the 2009 FCS National Championship . The Wildcats played in the NCAA Division I Football Championship game on December 18 , 2009 against the Montana Grizzlies . The Wildcats beat the Grizzlies 23 -- 21 to win their first NCAA Division I - AA National Championship . Villanova played in bowl games following the 1936 , 1947 , 1948 , 1961 , and 1962 college football seasons . After 87 seasons , the Board of Trustees voted to drop Football in April 1981 due to financial losses and poor attendance . In April , 1984 , the Board of Trustees agreed to reinstate Football at a lower level as a non-scholarship program ( Division I schools could field a non-scholarship Division III program at the time ) and named Andy Talley as the head coach , with first Division III practice that fall and first . The program began competing in Division I - AA ( now Division I FCS ) level during the 1988 season . Villanova football has sent 36 players to the NFL over the years including Hall of Fame defensive end Howie Long , formerly of the Oakland Raiders and All - Pro running back Brian Westbrook of the Philadelphia Eagles . Villanova plays the Delaware Fightin ' Blue Hens in the `` Battle of the Blue '' . Villanova leads the all - time series which was first played in 1895 by the margin of 23 - 21 - 1 . The Wildcats have a current four - year series where they will play the Temple Owls for the Philadelphia `` Mayor 's Cup '' . Villanova won the inaugural game in September 2009 but dropped the next two games to the FBS school . Villanova still leads the all - time series that started in 1928 by the margin of 16 - 14 - 2 . The Wildcats also play the Penn Quakers in most recent seasons with many of the games held at historic Franklin Field . The series was first played in 1905 and Villanova has an 11 - 5 lead . There has been some discussion regarding a potential promotion to the Football Bowl Subdivision and into the Big East in which they already participate for all other Sports . In September 2010 , the Big East informally spoke with Villanova about joining for football . The school conducted several feasibility studies but a scheduled April 12 , 2011 Board of Trustees vote was never taken after several Big East Football ( now the American Athletic Conference ) schools objected to their use of Talen Energy Stadium , then known as PPL Park , as an unacceptable venue for future games . The stadium currently holds only 18,500 but is expandable at the discretion of the Philadelphia Union soccer organization . Men 's Lacrosse ( edit ) Main article : Villanova Wildcats men 's lacrosse The Villanova Wildcats men 's lacrosse team represents Villanova University in National Collegiate Athletic Association ( NCAA ) Division I men 's lacrosse . Villanova currently competes as a member of the Big East Conference and plays their home games at Villanova Stadium in Villanova , Pennsylvania . Coach Michael Corrado has taken the team to its only two NCAA appearances in history during his 6 - year tenure and the school is poised for greater success in upcoming seasons . Villanova rose as high as # 7 ranking and qualified for an at - large bid in the 2011 NCAA Tournament where they lost to the University of Denver in the first round . During the regular season , the Wildcats drew over 6500 fans to a Big East match - up with Syracuse setting a new on - campus record for Lacrosse . Brian Karalunas became the first USILA First Team All - American in Villanova history . Through 2009 , Villanova men 's lacrosse was a member of the Colonial Athletic Association and won the CAA tournament for their first title in 2009 . The fourth - seeded Wildcats were the lowest - seeded championship team in conference history . That season , Villanova also made their first NCAA tournament appearance , where they were routed in the first round by first - seeded Virginia , 18 -- 6 . The 2004 team finished 13 - 3 playing against the stiff competition of the CAA . Track and field ( edit ) Villanova University 's Track and field team has a history of athletic success that has spanned from championships in both incarnations of the Big East Conference to NCAA championships . The men 's team has produced 69 NCAA championships , 36 indoor and 33 outdoor . The team has had 8 NCAA team championships -- 4 cross country , 3 indoor ( ' 68 , ' 71 , ' 79 ) , 1 outdoor ( ' 57 ) . Prior to NCAA sponsoring Indoor T&F in 1965 , Villanova won 6 ICAAAA Indoor T&F Championships ( ' 57 , ' 58 , ' 60 , ' 62 , ' 63 , ' 64 ) . Villanova has produced 28 athletes who have made appearances in the Olympics , 10 of whom have medaled ( 7 Gold medals , 3 Silver medals ) . The men 's team has also won 112 Penn Relays Championships , which stands as the most wins by any school . The men 's current coaches include head coach , Marcus O'Sullivan , and assistant head coach , Anthony Williams . The women 's team has also had a multitude of success , producing 10 Big East team Championships and 7 NCAA team Championships . They have also produced 7 Olympians including Vicki Huber , Sonia O'Sullivan , Kim Certain , Kate Fonshell , Jen Rhines , Carmen Douma , and Carrie Tollefson . The Women 's team has won 28 Penn Relays Championships , which is the most wins by any women 's program . The current women 's coaches include head coach , Gina Procaccio , and assistant head coach , Anthony Williams . At least one Villanova athlete has competed in every Summer Olympics since 1948 , winning a total of 13 medals ( 9 gold , 4 silver ) . Cross Country ( edit ) Villanova Men 's and Women 's Cross Country teams have a successful history of Big East and NCAA National Championships . Villanova won both the Men 's and Women 's Big East Cross Country Team Titles in 2011 . The 2011 women 's Cross Country team finished as national runner - up led by Sheila Reid individual title . In 2010 and 2009 , the women 's cross country team won the NCAA Women 's Cross Country Championship under Coach Gina Procaccio . The 2010 victory was led by individual national champion Sheila Reid of Villanova who repeated her NCAA individual crown in 2011 . The Wildcats hold the NCAA Division I record for the most NCAA Team and Individual Women 's Cross Country Champions with 9 NCAA Team Championships ( ' 89 , ' 90 , ' 91 , ' 92 , ' 93 , ' 94 , ' 98 , ' 09 , ' 10 ) and 9 NCAA individual champions , 7 of which coincided . NCAA Individual Cross Country Champions Vicki Huber 1989 Sonia O'Sullivan 1990 , 1991 Carole Zajac 1992 , 1993 Jennifer Rhines 1994 Carrie Tollefson 1997 Sheila Reid 2010 , 2011 The 2011 Villanova Men 's Cross Country team finished 13th in the Team competition at NCAA meet . Villanova has won 4 NCAA Men 's Cross Country Team Championships covering 1966 , 1967 , 1968 and 1970 . NCAA Individual Cross Country Champions Victor Zwolak 1963 Patrick Tiernan 2016 Swimming and Diving ( edit ) Main article : Villanova Swimming and Diving In its history , Villanova Swimming and Diving has produced several Olympians . Most recently Maddy Crippen competed in the 400m individual medley at the 2000 Olympics . At the 2008 Olympics , Villanova was represented by Kristina Lennox - Silva . Lennox competed for Puerto Rico and swam the 400m freestyle and 200m butterfly . NCAA team Championships ( edit ) Villanova has 21 NCAA team national championships . Men 's ( 12 ) Basketball ( 3 ) : 1985 , 2016 , 2018 Cross Country ( 4 ) : 1966 , 1967 , 1968 , 1970 Football ( 1 ) : 2009 Indoor Track & Field ( 3 ) : 1968 , 1971 , 1979 Outdoor Track & Field ( 1 ) : 1957 Women 's ( 9 ) Cross Country ( 9 ) : 1989 , 1990 , 1991 , 1992 , 1993 , 1994 , 1998 , 2009 , 2010 see also : Big East Conference NCAA team championships List of NCAA schools with the most NCAA Division I championships Conference realignment ( edit ) In December 2012 the presidents of seven Big East schools which do not sponsor FBS football ( also sometimes referred to as the `` Catholic 7 '' ) , including Villanova , voted unanimously to leave the Big East and form a new conference . The new conference , which kept the Big East name , officially began on July 1 , 2013 . Notable non varsity Sports ( edit ) Rugby ( edit ) Villanova Ruby Football Club University Villanova University Association USA Rugby Conference Keystone Conference The Villanova Rugby Football Club regained its official sanctioning by the University in 2010 , after losing this status and being classified as a recreational sport during the 1990s . The college rugby team has been able to develop a roster of over 50 players , due in part to the growing popularity of rugby at the high school level , and the Wildcats are supported by a network of rugby alumni that contribute towards the cost of the rugby program . The Wildcats are led by head coach Jack Foley , a former Villanova RFC athlete , USA 7 's player , and a head coach at various programs since 1998 . Recently , the Wildcats played at the 2013 Collegiate Rugby Championship , the highest profile competition in college rugby , which was broadcast live on NBC from PPL Park in Philadelphia . Currently , Villanova competes in the D1 - AA Keystone Conference for both 15 's and 7 's rugby . The team also schedules out of conference games , such as its preseaon wins over Columbia , UPenn , and Lehigh in the fall of 2016 . Following its regular spring sevens schedule , the team also competes in the annual Philadelphia Cup at PPL Park which runs concurrent with the CRC . Winning the Philadelphia Cup guarantees the Wildcats a spot in the CRC for the next year . See also ( edit ) Sports in Philadelphia # Collegiate sports References ( edit ) Jump up ^ Villanova Athletics Identity Standards Guide ( PDF ) . June 26 , 2012 . Retrieved April 10 , 2016 . Jump up ^ `` Seven basketball - only schools leaving the Big East to start new conference '' . NCAA.com . National Collegiate Athletic Association . Associated Press . December 17 , 2012 . Retrieved March 27 , 2016 . Jump up ^ `` Seven schools leaving Big East '' . ESPN . December 15 , 2012 . Retrieved December 16 , 2012 . Jump up ^ `` Villanova.com Harry Perretta Bio - Official Athletic Site Official Athletic Site - Women 's Basketball '' . Jump up ^ `` Harry Perreta '' . Villanova University . Jump up ^ 2009 Villanova Men 's Lacrosse Quick Facts ( PDF ) , Villanova University , retrieved May 14 , 2009 . Jump up ^ Villanova claims first CAA title with 10 - 9 win over Towson Archived May 6 , 2009 , at the Wayback Machine. , Inside Lacrosse , May 2 , 2009 . Jump up ^ Villanova Secures First CAA Men 's Lacrosse Title , National Collegiate Athletic Association , May 3 , 2009 . Jump up ^ Virginia crushes Villanova , 18 -- 6 , faces Hopkins in next round , The Baltimore Sun , May 11 , 2009 . ^ Jump up to : `` RUNNOVA '' . Retrieved 2008 - 02 - 20 . Jump up ^ Villanova magazine , Summer 2008 , `` Villanovans have won 20 Olympic Medals '' Jump up ^ `` 2011 DI mens team cross country results '' . NCAA.com . Jump up ^ http://fs.ncaa.org/Docs/stats/champs_records_book/Overall.pdf ^ Jump up to : The Villanovan , University restores club charter to men 's rugby Sep. 22 , 2010 Jump up ^ Philly.com , Orphaned Rugby Club Wins On The Main Line Without Villanova , Dec. 24 , 1997 , http://articles.philly.com/1997-12-24/sports/25553859_1_screening-athletes-usa-rugby-football-union-rugby-injury Jump up ^ `` Villanova Rugby '' . Villanova University Rugby Football Club . External links ( edit ) Official website Villanova University Academics School of Business School of Law Campus Arboretum Villanova St. Thomas of Villanova Church Villanova , PA People Alumni List of Presidents Fr . Peter Donohue ( President ) Order of Saint Augustine ( O.S.A. ) Media The Villanovan WXVU Athletics Villanova Wildcats Holy War Men 's basketball Women 's basketball Men 's lacrosse Football ( Battle of the Blue ) The Pavilion Villanova Stadium Jake Nevin Field House Catholicism portal Links to related articles Big East Conference Full members Butler Bulldogs Creighton Bluejays DePaul Blue Demons Georgetown Hoyas Marquette Golden Eagles Providence Friars St. John 's Red Storm Seton Hall Pirates Villanova Wildcats Xavier Musketeers Associate members Cincinnati Bearcats ( women 's lacrosse ; leaving in 2018 ) Connecticut Huskies ( field hockey , women 's lacrosse ; lacrosse leaving in 2018 ) Denver Pioneers ( men 's lacrosse , women 's lacrosse ) Florida Gators ( women 's lacrosse ; leaving in 2018 ) Liberty Lady Flames ( field hockey ) Old Dominion Monarchs ( field hockey ; women 's lacrosse joining in 2018 ) Quinnipiac Bobcats ( field hockey ) Temple Owls ( field hockey , women 's lacrosse ; lacrosse leaving in 2018 ) Vanderbilt Commodores ( women 's lacrosse ; leaving in 2018 ) History Big East Conference ( 1979 -- 2013 ) 2010 -- 13 Big East realignment Colonial Athletic Association Full members Charleston Cougars Delaware Fightin ' Blue Hens Drexel Dragons Elon Phoenix Hofstra Pride James Madison Dukes Northeastern Huskies Towson Tigers UNC Wilmington Seahawks William & Mary Tribe Football - only members Albany Great Danes Maine Black Bears New Hampshire Wildcats Rhode Island Rams Richmond Spiders Stony Brook Seawolves Villanova Wildcats Lacrosse - only members Fairfield Stags Massachusetts Minutemen Other associate members Eastern Michigan Eagles ( women 's rowing ) Villanova Wildcats ( football and women 's rowing ) History 2010 -- 13 Colonial Athletic Association realignment Sports teams based in and around Philadelphia Baseball MLB Philadelphia Phillies IL Lehigh Valley IronPigs EL Reading Fightin Phils Trenton Thunder CL Wilmington Blue Rocks Basketball NBA Philadelphia 76ers G League Delaware Blue Coats Football NFL Philadelphia Eagles AFL Philadelphia Soul NAL Lehigh Valley Steelhawks WFA Philadelphia Phantomz IWFL Philadelphia Firebirds Hockey NHL Philadelphia Flyers AHL Lehigh Valley Phantoms ECHL Reading Royals NAHL Philadelphia Rebels EHL Philadelphia Little Flyers Philadelphia Junior Flyers Philadelphia Revolution Rugby league USARL Bucks County Sharks Delaware Black Foxes Philadelphia Fight Roller derby WFTDA Diamond State Roller Girls Philly Roller Derby Soccer MLS Philadelphia Union USL Bethlehem Steel FC NPSL Junior Lone Star FC PDL Lehigh Valley United Sonic Reading United A.C. ASL Philadelphia Fury Tennis WTT Philadelphia Freedoms Lacrosse NLL Philadelphia Wings College athletics ( NCAA Div . I ) Drexel University Dragons La Salle University Explorers Saint Joseph 's University Hawks Temple University Owls University of Pennsylvania Quakers Villanova University Wildcats Lafayette College Leopards Lehigh University Mountain Hawks Rider University Broncs University of Delaware Blue Hens Princeton University Tigers See also : Philadelphia Big 5 and City 6 College athletics ( NCAA Div. II ) Philadelphia University Rams University of the Sciences Devils West Chester University Golden Rams Wilmington University Wildcats Currently defunct teams Further information : Template : Defunct Philadelphia sports teams Main article : Sports in Philadelphia Retrieved from `` https://en.wikipedia.org/w/index.php?title=Villanova_Wildcats&oldid=835350602 '' Categories : Villanova Wildcats Philadelphia Big 5 Hidden categories : Webarchive template wayback links All articles with dead external links Articles with dead external links from July 2016 Articles with permanently dead external links Talk Contents About Wikipedia Español Français Polski 中文 Edit links This page was last edited on 8 April 2018 , at 04 : 42 . Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply . By using this site , you agree to the Terms of Use and Privacy Policy . 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Question: when was the last time villanova won the ncaa basketball championship


Transformer types - wikipedia Transformer types Jump to : navigation , search Circuit symbols Transformer with two windings and iron core . Transformer with three windings . The dots show the relative configuration of the windings . Transformer with electrostatic screen preventing capacitive coupling between the windings . An electric arc furnace the transformer has heavy copper bus for the low voltage winding , which can be rated for tens of thousands of amperes . They are immersed in oil for cooling and insulation , and are designed to survive frequent short circuits . A variety of types of electrical transformer are made for different purposes . Despite their design differences , the various types employ the same basic principle as discovered in 1831 by Michael Faraday , and share several key functional parts . Contents ( hide ) 1 Power transformers 1.1 Laminated core 1.2 Toroidal 1.3 Autotransformer 1.4 Variable autotransformer 1.5 Induction regulator 1.6 Polyphase transformer 1.7 Grounding transformer 1.8 Phase - shifting transformer 1.9 Variable - frequency transformer 1.10 Leakage or stray field transformers 1.10. 1 Uses 1.11 Resonant transformer 1.11. 1 Constant voltage transformer 1.12 Ferrite core 1.12. 1 Planar transformer 1.13 Oil cooled transformer 1.14 Cast resin transformer 1.15 Isolating transformer 2 Instrument transformer 2.1 Current transformer 2.2 Voltage transformer or potential transformer 2.3 Combined instrument transformer 3 Pulse transformer 4 RF transformer 4.1 Air - core transformer 4.2 Ferrite - core transformer 4.3 Transmission - line transformer 4.4 Balun 5 IF transformer 6 Audio transformer 6.1 Loudspeaker transformer 6.2 Output transformer 6.3 Small signal transformer 6.4 Interstage and coupling transformers 7 Other types 7.1 Transactor 7.2 Hedgehog 7.3 Variometer and variocoupler 7.4 Rotary transformer 7.5 Variable differential transformer 7.6 Resolver and synchro 8 See also 9 References Power transformers ( edit ) Laminated core ( edit ) Laminated core transformer This is the most common type of transformer , widely used in electric power transmission and appliances to convert mains voltage to low voltage to power electronic devices . They are available in power ratings ranging from mW to MW . The insulated laminations minimizes eddy current losses in the iron core . Small appliance and electronic transformers may use a split bobbin , giving a high level of insulation between the windings . The rectangular cores are made up of stampings , often in E-I shape pairs , but other shapes are sometimes used . Shields between primary and secondary may be fitted to reduce EMI ( electromagnetic interference ) , or a screen winding is occasionally used . Small appliance and electronics transformers may have a thermal cut - out built into the winding , to shut - off power at high temperatures to prevent further overheating . Toroidal ( edit ) Toroidal transformer Doughnut shaped toroidal transformers save space compared to E-I cores , and may reduce external magnetic field . These use a ring shaped core , copper windings wrapped round this ring ( and thus threaded through the ring during winding ) , and tape for insulation . Toroidal transformers have a lower external magnetic field compared to rectangular transformers , and can be smaller for a given power rating . However , they cost more to make , as winding requires more complex and slower equipment . They can be mounted by a bolt through the center , using washers and rubber pads or by potting in resin . Autotransformer ( edit ) Main article : Autotransformer An autotransformer has one winding that is tapped at some point along the winding . Voltage is applied across a portion of the winding , and a higher ( or lower ) voltage is produced across another portion of the same winding . The equivalent power rating of the autotransfomer is lower than the actual load power rating . It is calculated by : load VA × ( Vin -- Vout ) / Vin . For example , an auto transformer that adapts a 1000 VA load rated at 120 Volts to a 240 Volt supply has an equivalent rating of at least : 1,000 VA × ( 240V -- 120V ) / 240V = 500VA . However , the actual rating ( shown on the tally plate ) must be at least 1000 VA . For voltage ratios that do n't exceed about 3 : 1 , an autotransformer is cheaper , lighter , smaller , and more efficient than an isolating ( two - winding ) transformer of the same rating . Large three - phase autotransformers are used in electric power distribution systems , for example , to interconnect 33 kV and 66 kV sub-transmission networks . Variable autotransformer ( edit ) Variable autotransformer Main article : Autotransformer § Variable autotransformers By exposing part of the winding coils of an autotransformer , and making the secondary connection through a sliding carbon brush , an autotransformer with a near - continuously variable turns ratio can be obtained , allowing for wide voltage adjustment in very small increments . Induction regulator ( edit ) Main article : Induction regulator The induction regulator is similar in design to a wound - rotor induction motor but it is essentially a transformer whose output voltage is varied by rotating its secondary relative to the primary -- i.e. , rotating the angular position of the rotor . It can be seen as a power transformer exploiting rotating magnetic fields . The major advantage of the induction regulator is that unlike variacs , they are practical for transformers over 5 kVA . Hence , such regulators find widespread use in high - voltage laboratories . Polyphase transformer ( edit ) A high - voltage transformer being dismantled Cutaway view of a polyphase transformer For polyphase systems , multiple single - phase transformers can be used , or all phases can be connected to a single polyphase transformer . For a three phase transformer , the three primary windings are connected together and the three secondary windings are connected together . Examples of connections are wye - delta , delta - wye , delta - delta and wye - wye . 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 wye winding . If the secondary is a delta winding , the ground may be connected to a center tap on one winding ( high leg delta ) or one phase may be grounded ( corner grounded delta ) . A special purpose polyphase transformer is the zigzag transformer . There are many possible configurations that may involve more or fewer than six windings and various tap connections . Three - phase transformers 380kV / 110kV and 110kV / 20kV Grounding transformer ( edit ) Main article : Earthing transformer Grounding or earthing transformers let three wire ( delta ) polyphase system supplies accommodate phase to neutral loads by providing a return path for current to a neutral . Grounding transformers most commonly incorporate a single winding transformer with a zigzag winding configuration but may also be created with a wye - delta isolated winding transformer connection . Phase - shifting transformer ( edit ) Main article : Quadrature booster This is a specialized type of transformer which can be configured to adjust the phase relationship between input and output . This allows power flow in an electric grid to be controlled , e.g. to steer power flows away from a shorter ( but overloaded ) link to a longer path with excess capacity . Variable - frequency transformer ( edit ) Main article : Variable - frequency transformer A variable - frequency transformer is a specialized three - phase power transformer which allows the phase relationship between the input and output windings to be continuously adjusted by rotating one half . They are used to interconnect electrical grids with the same nominal frequency but without synchronous phase coordination . Leakage or stray field transformers ( edit ) Leakage transformer A leakage transformer , also called a stray - field transformer , has a significantly higher leakage inductance than other transformers , sometimes increased by a magnetic bypass or shunt in its core between primary and secondary , which is sometimes adjustable with a set screw . This provides a transformer with an inherent current limitation due to the loose coupling between its primary and the secondary windings . In this case , it is short - circuit inductance which is actually acting as a current limiting parameter . The output and input currents are low enough to prevent thermal overload under all load conditions -- even if the secondary is shorted . Uses ( edit ) Leakage transformers are used for arc welding and high voltage discharge lamps ( neon lights and cold cathode fluorescent lamps , which are series connected up to 7.5 kV AC ) . It acts then both as a voltage transformer and as a magnetic ballast . Other applications are short - circuit - proof extra-low voltage transformers for toys or doorbell installations . Resonant transformer ( edit ) Further information : Resonant inductive coupling Further information : Tesla coil § Resonant transformer A resonant transformer is a transformer in which one or both windings has a capacitor across it and functions as a tuned circuit . Used at radio frequencies , resonant transformers can function as high Q factor bandpass filters . The transformer windings have either air or ferrite cores and the bandwidth can be adjusted by varying the coupling ( mutual inductance ) . One common form is the IF ( intermediate frequency ) transformer , used in superheterodyne radio receivers . They are also used in radio transmitters . Resonant transformers are also used in electronic ballasts for gas discharge lamps , and high voltage power supplies . They are also used in some types of switching power supplies . Here the short - circuit inductance value is an important parameter that determines the resonance frequency of the resonant transformer . Often only secondary winding has a resonant capacitor ( or stray capacitance ) and acts as a serial resonant tank circuit . When the short - circuit inductance of the secondary side of the transformer is L and the resonant capacitor ( or stray capacitance ) of the secondary side is C , The resonance frequency ω of 1 ' is as follows ω s = 1 L s c C r = 1 ( 1 − k 2 ) L s C r ( \ displaystyle \ omega _ ( s ) = ( \ frac ( 1 ) ( \ sqrt ( L_ ( sc ) C_ ( r ) ) ) ) = ( \ frac ( 1 ) ( \ sqrt ( ( 1 - k ^ ( 2 ) ) L_ ( s ) C_ ( r ) ) ) ) ) The transformer is driven by a pulse or square wave for efficiency , generated by an electronic oscillator circuit . Each pulse serves to drive resonant sinusoidal oscillations in the tuned winding , and due to resonance a high voltage can be developed across the secondary . Applications : Intermediate frequency ( IF ) transformer in superheterodyne radio receiver Tank transformers in radio transmitters Tesla coil CCFL inverter Oudin coil ( or Oudin resonator ; named after its inventor Paul Oudin ) D'Arsonval apparatus Ignition coil or induction coil used in the ignition system of a petrol engine Electrical breakdown and insulation testing of high voltage equipment and cables . In the latter case , the transformer 's secondary is resonated with the cable 's capacitance . Constant voltage transformer ( edit ) See also : Voltage regulator § Constant - voltage transformer By arranging particular magnetic properties of a transformer core , and installing a ferro - resonant tank circuit ( a capacitor and an additional winding ) , a transformer can be arranged to automatically keep the secondary winding voltage relatively constant for varying primary supply without additional circuitry or manual adjustment . Ferro - resonant transformers run hotter than standard power transformers , because regulating action depends on core saturation , which reduces efficiency . The output waveform is heavily distorted unless careful measures are taken to prevent this . Saturating transformers provide a simple rugged method to stabilize an AC power supply . Ferrite core ( edit ) Ferrite core power transformers are widely used in switched - mode power supplies ( SMPSs ) . The powder core enables high - frequency operation , and hence much smaller size - to - power ratio than laminated - iron transformers . Ferrite transformers are not used as power transformers at mains frequency since laminated iron cores cost less than an equivalent ferrite core . Planar transformer ( edit ) A planar transformer Exploded view : the spiral primary `` winding '' on one side of the PCB ( the spiral secondary `` winding '' is on the other side of the PCB ) Manufacturers etch spiral patterns on a printed circuit board to form the `` windings '' of a planar transformer , replacing the turns of wire used to make other types . Some planar transformers are commercially sold as discrete components . Other planar transformers are one of many components on a printed circuit board . A planar transformer can be thinner than other transformers , which is useful for low - profile applications or when several printed circuit boards are stacked . Almost all planar transformers use a ferrite planar core . Oil cooled transformer ( edit ) Large transformers used in power distribution or electrical substations have their core and coils immersed in oil , which cools and insulates . Oil circulates through ducts in the coil and around the coil and core assembly , moved by convection . The oil is cooled by the outside of the tank in small ratings , and by an air - cooled radiator in larger ratings . Where a higher rating is required , or where the transformer is in a building or underground , oil pumps circulate the oil , and an oil - to - water heat exchanger may also be used . Some transformers may contain PCBs where or when its use was permitted . For example , until 1979 in South Africa . substitute fire - resistant liquids such as silicone oils are now used instead . Cast resin transformer ( edit ) Cast - resin power transformers encase the windings in epoxy resin . These transformers simplify installation since they are dry , without cooling oil , and so require no fire - proof vault for indoor installations . The epoxy protects the windings from dust and corrosive atmospheres . However , because the molds for casting the coils are only available in fixed sizes , the design of the transformers is less flexible , which may make them more costly if customized features ( voltage , turns ratio , taps ) are required . Isolating transformer ( edit ) An isolation transformer links two circuits magnetically , but provides no metallic conductive path between the circuits . An example application would be in the power supply for medical equipment , when it is necessary to prevent any leakage from the AC power system into devices connected to a patient . Special purpose isolation transformers may include shielding to prevent coupling of electromagnetic noise between circuits , or may have reinforced insulation to withstand thousands of volts of potential difference between primary and secondary circuits . Instrument transformer ( edit ) Main article : Instrument transformer Instrument transformers Instrument transformers are typically used to operate instruments from high voltage lines or high current circuits , safely isolating measurement and control circuitry from the high voltages or currents . The primary winding of the transformer is connected to the high voltage or high current circuit , and the meter or relay is connected to the secondary circuit . Instrument transformers may also be used as an isolation transformer so that secondary quantities may be used without affecting the primary circuitry . Terminal identifications ( either alphanumeric such as H , X , Y , etc. or a colored spot or dot impressed in the case ) indicate one end of each winding , indicating the same instantaneous polarity and phase between windings . This applies to both types of instrument transformers . Correct identification of terminals and wiring is essential for proper operation of metering and protective relay instrumentation . Current transformer ( edit ) Main article : Current transformer Current transformers used in metering equipment for three - phase 400 ampere electricity supply A current transformer ( CT ) is a series connected measurement device designed to provide a current in its secondary coil proportional to the current flowing in its primary . Current transformers are commonly used in metering and protective relays in the electrical power industry . Current transformers are often constructed by passing a single primary turn ( either an insulated cable or an uninsulated bus bar ) through a well - insulated toroidal core wrapped with many turns of wire . The CT is typically described by its current ratio from primary to secondary . For example , a 1000 : 1 CT provides an output current of 1 amperes when 1000 amperes flow through the primary winding . Standard secondary current ratings are 5 amperes or 1 ampere , compatible with standard measuring instruments . The secondary winding can be single ratio or have several tap points to provide a range of ratios . Care must be taken to make sure the secondary winding is not disconnected from its low - impedance load while current flows in the primary , as this may produce a dangerously high voltage across the open secondary and may permanently affect the accuracy of the transformer . Specially constructed wideband CTs are also used , usually with an oscilloscope , to measure high frequency waveforms or pulsed currents within pulsed power systems . One type provides a voltage output that is proportional to the measured current . Another , called a Rogowski coil , requires an external integrator in order to provide a proportional output . A current clamp uses a current transformer with a split core that can be easily wrapped around a conductor in a circuit . This is a common method used in portable current measuring instruments but permanent installations use more economical types of current transformer . Voltage transformer or potential transformer ( edit ) Voltage transformers ( VT ) , also called potential transformers ( PT ) , are a parallel connected type of instrument transformer , used for metering and protection in high - voltage circuits or phasor phase shift isolation . They are designed to present negligible load to the supply being measured and to have an accurate voltage ratio to enable accurate metering . A potential transformer may have several secondary windings on the same core as a primary winding , for use in different metering or protection circuits . The primary may be connected phase to ground or phase to phase . The secondary is usually grounded on one terminal . There are three primary types of voltage transformers ( VT ) : electromagnetic , capacitor , and optical . The electromagnetic voltage transformer is a wire - wound transformer . The capacitor voltage transformer uses a capacitance potential divider and is used at higher voltages due to a lower cost than an electromagnetic VT . An optical voltage transformer exploits the electrical properties of optical materials . Measurement of high voltages is possible by the potential transformers . Combined instrument transformer ( edit ) Combined instrument transformer A combined instrument transformer encloses a current transformer and a voltage transformer in the same transformer . There are two main combined current and voltage transformer designs : oil - paper insulated and SF insulated . One advantage of applying this solution is reduced substation footprint , due to reduced number of transformers in a bay , supporting structures and connections as well as lower costs for civil works , transportation and installation . Pulse transformer ( edit ) Bothhand TS6121A pulse transformer 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 relatively constant amplitude ) . Small versions called signal types are used in digital logic and telecommunications circuits , often for matching logic drivers to transmission lines . 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 semiconductors . Special high voltage pulse transformers are also used to generate high power pulses for radar , particle accelerators , or other high energy pulsed power applications . To minimize 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 . Pulse transformers by definition have a duty cycle of less than 0.5 ; whatever energy stored in the coil during the pulse must be `` dumped '' out before the pulse is fired again . RF transformer ( edit ) There are several types of transformer used in radio frequency ( RF ) work . Laminated steel is not suitable for RF . Air - core transformer ( edit ) These are used for high frequency work . The lack of a core means very low inductance . All current excites current and induces secondary voltage which is proportional to the mutual inductance . Such transformers may be nothing more than a few turns of wire soldered onto a printed circuit board . Ferrite - core transformer ( edit ) Ferrite - core transformers are widely used in impedance matching transformers for RF , especially for baluns ( see below ) for TV and radio antennas . Many only have one or two turns . Transmission - line transformer ( edit ) For radio frequency use , transformers are sometimes made from configurations of transmission line , sometimes bifilar or coaxial cable , wound around ferrite or other types of core . This style of transformer gives an extremely wide bandwidth but only a limited number of ratios ( such as 1 : 9 , 1 : 4 or 1 : 2 ) can be achieved with this technique . The core material increases the inductance dramatically , thereby raising its Q factor . The cores of such transformers help improve performance at the lower frequency end of the band . RF transformers sometimes used a third coil ( called a tickler winding ) to inject feedback into an earlier ( detector ) stage in antique regenerative radio receivers . In RF and microwave systems , a quarter - wave impedance transformer provides a way of matching impedances between circuits over a limited range of frequencies , using only a length of transmission line . The line may be coaxial cable , waveguide , stripline or microstripline . Balun ( edit ) Main article : Balun Baluns are transformers designed specifically to connect between balanced ( non-grounded ) and unbalanced ( grounded ) circuits . These are sometimes made from configurations of transmission line and sometimes bifilar or coaxial cable and are similar to transmission line transformers in construction and operation . Baluns can be designed to not only interface between balanced and unbalanced loads , but to additionally provide impedance matching between those load types . IF transformer ( edit ) Ferrite - core transformers are widely used in ( intermediate frequency ) ( IF ) stages in superheterodyne radio receivers . They are mostly tuned transformers , containing a threaded ferrite slug that is screwed in or out to adjust IF tuning . The transformers are usually canned ( shielded ) for stability and to reduce interference . Audio transformer ( edit ) Two speaker - level audio transformers in a tube amplifier are seen on the left . The power supply toroidal transformer is on right Five audio transformers for various line level purposes . The two black boxes on the left contain 1 : 1 transformers for splitting signals , balancing unbalanced signals , or isolating two different AC ground systems to eliminate buzz and hum . The two cylindrical metal cases fit into octal sockets ; each one contains a 1 : 1 line transformer , the first is rated at 600 ohms , the second is rated at 15,000 ohms . On the far right is a DI unit ; its 12 : 1 transformer ( with yellow insulation ) changes a high impedance unbalanced input to a low impedance balanced output . Audio transformers are those specifically designed for use in audio circuits to carry audio signal . They can be used to block radio frequency interference or the DC component of an audio signal , to split or combine audio signals , or to provide impedance matching between high impedance and low impedance circuits , such as between a high impedance tube ( valve ) amplifier output and a low impedance loudspeaker , or between a high impedance instrument output and the low impedance input of a mixing console . Audio transformers that operate with loudspeaker voltages and current are larger than those that operate at microphone or line level , which carry much less power . Bridge transformers connect 2 - wire and 4 - wire communication circuits . Being magnetic devices , audio transformers are susceptible to external magnetic fields such as those generated by AC current - carrying conductors . `` Hum '' is a term commonly used to describe unwanted signals originating from the `` mains '' power supply ( typically 50 or 60 Hz ) . Audio transformers used for low - level signals , such as those from microphones , often include magnetic shielding to protect against extraneous magnetically coupled signals . Audio transformers were originally designed to connect different telephone systems to one another while keeping their respective power supplies isolated , and are still commonly used to interconnect professional audio systems or system components , to eliminate buzz and hum . Such transformers typically have a 1 : 1 ratio between the primary and the secondary . These can also be used for splitting signals , balancing unbalanced signals , or feeding a balanced signal to unbalanced equipment . Transformers are also used in DI boxes to convert high - impedance instrument signals ( e.g. , bass guitar ) to low impedance signals to enable them to connect to a microphone input on the mixing console . A particularly critical component is the output transformer of a valve amplifier . Valve circuits for quality reproduction have long been produced with no other ( inter-stage ) audio transformers , but an output transformer is needed to couple the relatively high impedance ( up to a few hundred ohms depending upon configuration ) of the output valve ( s ) to the low impedance of a loudspeaker . ( The valves can deliver a low current at a high voltage ; the speakers require high current at low voltage . ) Most solid - state power amplifiers need no output transformer at all . Audio transformers affect the sound quality because they are non-linear . Harmonic distortion is added to the original signal , especially odd - order harmonics with an emphasis on third - order harmonics . When the incoming signal amplitude is very low there is not enough level to energize the magnetic core ( see coercivity and magnetic hysteresis ) . When the incoming signal amplitude is very high the transformer saturates and adds ringing harmonics . Another non-linearity comes from limited frequency response . For good low - frequency response a relatively large magnetic core is required ; high power handling increases the required core size . Good high - frequency response requires carefully designed and implemented windings without excessive leakage inductance or stray capacitance . All this makes for an expensive component . Early transistor audio power amplifiers often had output transformers , but they were eliminated as advances in semiconductors allowed the design of amplifiers with sufficiently low output impedance to drive a loudspeaker directly . Loudspeaker transformer ( edit ) Loudspeaker transformer in old radio In the same way that transformers create high voltage power transmission circuits that minimize transmission losses , loudspeaker transformers can power many individual loudspeakers from a single audio circuit operated at higher than normal loudspeaker voltages . This application is common in public address applications . Such circuits are commonly referred to as constant - voltage speaker systems . Such systems are also known by the nominal voltage of the loudspeaker line , such as 25 - , 70 - and 100 - volt speaker systems ( the voltage corresponding to the power rating of a speaker or amplifier ) . A transformer steps up the output of the system 's amplifer to the distribution voltage . At the distant loudspeaker locations , a step - down transformer matches the speaker to the rated voltage of the line , so the speaker produces rated nominal output when the line is at nominal voltage . Loudspeaker transformers commonly have multiple primary taps to adjust the volume at each speaker in steps . Output transformer ( edit ) Valve ( tube ) amplifiers almost always use an output transformer to match the high load impedance requirement of the valves ( several kilohms ) to a low impedance speaker Small signal transformer ( edit ) Moving coil phonograph cartridges produce a very small voltage . For this to be amplified with a reasonable signal - noise ratio usually requires a transformer to convert the voltage to the range of the more common moving - magnet cartridges . Microphones may also be matched to their load with a small transformer , which is mumetal shielded to minimise noise pickup . These transformers are less widely used today , as transistorized buffers are now cheaper . Interstage and coupling transformers ( edit ) In a push -- pull amplifier , an inverted signal is required and can be obtained from a transformer with a center - tapped winding , used to drive two active devices in opposite phase . These phase splitting transformers are not much used today . Other types ( edit ) This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . ( January 2013 ) ( Learn how and when to remove this template message ) Transactor ( edit ) A transactor is a combination of a transformer and a reactor . A transactor has an iron core with an air - gap , which limits the coupling between windings . Hedgehog ( edit ) Hedgehog transformers are occasionally encountered in homemade 1920s radios . They are homemade audio interstage coupling transformers . Enamelled copper wire is wound round the central half of the length of a bundle of insulated iron wire ( e.g. , florists ' wire ) , to make the windings . The ends of the iron wires are then bent around the electrical winding to complete the magnetic circuit , and the whole is wrapped with tape or string to hold it together . Variometer and variocoupler ( edit ) Variometer used in 1920s radio receiver A variometer is a type of continuously variable air - core RF inductor with two windings . One common form consisted of a coil wound on a short hollow cylindrical form , with a second smaller coil inside , mounted on a shaft so its magnetic axis can be rotated with respect to the outer coil . The two coils are connected in series . When the two coils are collinear , with their magnetic fields pointed in the same direction , the two magnetic fields add , and the inductance is maximum . If the inner coil is rotated so its axis is at an angle to the outer coil , the magnetic fields do not add and the inductance is less . If the inner coil is rotated so it is collinear with the outer coil but their magnetic fields point in opposite directions , the fields cancel each other out and the inductance is very small or zero . The advantage of the variometer is that inductance can be adjusted continuously , over a wide range . Variometers were widely used in 1920s radio receivers . One of their main uses today is as antenna matching coils to match longwave radio transmitters to their antennas . The vario - coupler was a device with similar construction , but the two coils were not connected but attached to separate circuits . So it functioned as an air - core RF transformer with variable coupling . The inner coil could be rotated from 0 ° to 90 ° angle with the outer , reducing the mutual inductance from maximum to near zero . The pancake coil variometer was another common construction used in both 1920s receivers and transmitters . It consists of two flat spiral coils suspended vertically facing each other , hinged at one side so one could swing away from the other to an angle of 90 ° to reduce the coupling . The flat spiral design served to reduce parasitic capacitance and losses at radio frequencies . Pancake or `` honeycomb '' coil vario - couplers were used in the 1920s in the common Armstrong or `` tickler '' regenerative radio receivers . One coil was connected to the detector tube 's grid circuit . The other coil , the `` tickler '' coil was connected to the tube 's plate ( output ) circuit . It fed back some of the signal from the plate circuit into the input again , and this positive feedback increased the tube 's gain and selectivity . Rotary transformer ( edit ) Main article : Rotary transformer A rotary ( rotatory ) transformer is a specialized transformer that couples electrical signals between two parts that rotate in relation to each other -- as an alternative to slip rings , which are prone to wear and contact noise . They are commonly used in helical scan magnetic tape applications . Variable differential transformer ( edit ) Main articles : Linear variable differential transformer and rotary variable differential transformer A variable differential transformer is a rugged non-contact position sensor . It has two oppositely - phased primaries which nominally produce zero output in the secondary , but any movement of the core changes the coupling to produce a signal . Resolver and synchro ( edit ) Main articles : Resolver ( electrical ) and synchro The two - phase resolver and related three - phase synchro are rotary position sensors which work over a full 360 ° . The primary is rotated within two or three secondaries at different angles , and the amplitudes of the secondary signals can be decoded into an angle . Unlike variable differential transformers , the coils , and not just the core , move relative to each other , so slip rings are required to connect the primary . Resolvers produce in - phase and quadrature components which are useful for computation . Synchros produce three - phase signals which can be connected to other synchros to rotate them in a generator / motor configuration . See also ( edit ) Three - phase Three - phase electric power Buck -- boost transformer Tap changer Transformer Motor - generator References ( edit ) Jump up ^ `` The basics of autotransformers '' . ECMwebs . Jump up ^ Donald G. Fink & H. Wayne Beatty. ( 1978 ) . Standard Handbook for Electrical Engineers , 11th Edition . McGraw Hill , ISBN 0 - 07 - 020974 - X pp. 10 -- 44 and 10 -- 45 . Jump up ^ T.J. Gallagher and A.J. Pearmain ( 1983 ) : `` High Voltage - Measurement , Testing and Design '' , ISBN 0 - 471 - 90096 - 6 Jump up ^ `` 3 - Phase Step - Up Transformer '' , Agile Magnetics , Retrieved June 8 , 2016 . Jump up ^ Philips PM3311 Oscilloscope service manual Section 6.2. 16 ( describing the switch mode power supply ) , `` The unregulated d.c. voltage is applied in the form of pulses to a resonant transformer T1602 ... '' Jump up ^ `` Planar Transformer on a PCB '' Jump up ^ ANSI IEEE Standard C57. 12.00 General Requirements for Liquid - Immersed Distribution , Power and Regulating Transformers , 2000 Jump up ^ page 9 Jump up ^ UNEP Chemicals ( 1999 ) . Guidelines for the Identification of PCBs and Materials Containing PCBs ( PDF ) . United Nations Environment Programme . p. 2 . Retrieved 2007 - 11 - 07 . Jump up ^ ( 1 ) Jump up ^ ( 2 ) Jump up ^ `` Measurement Canada Standard Dwg . No. 3400 D3 Delta Connected CTs '' ( PDF ) . MEASUREMENT CANADA . Retrieved 12 December 2012 . Jump up ^ Network Protection & Automation , AREVA 2002 Jump up ^ `` The combined transformer - an optimal solution för HV substations , p. 1 '' ( PDF ) . Retrieved 9 July 2013 . Jump up ^ `` Combined instrument transformer , PVA 123 , p. 2 '' ( PDF ) . Retrieved 9 July 2013 . Jump up ^ Khanchandani , M.D. Singh , K.B. ( 2008 ) . Power electronics ( 2nd ed . ) . New Delhi : Tata McGraw - Hill . p. 76 . ISBN 9780070583894 . Jump up ^ `` Air Core Transformers '' , Virtual Institute of Applied Science , Retrieved June 8 , 2016 Jump up ^ Rumsey , Francis ; McCormick , Tim ( 2009 ) . Sound and recording ( 6th ed . ) . Oxford , UK : Focal Press . p. 356 . ISBN 978 - 0 - 240 - 52163 - 3 . Jump up ^ Robjohns , Hugh ( February 2010 ) . `` Analogue Warmth -- The Sound Of Tubes , Tape & Transformers '' . Sound On Sound . Jump up ^ The Institution of Engineering and Technology ( 1995 ) . Power system protection . London : Institution of Electrical Engineers . ISBN 0852968361 . Jump up ^ Douglas , Alan ( 1995 ) . Radio manufacturers of the 1920 's . Chandler , Ariz. : Sonoran Pub . p. 76 . ISBN 9781886606005 . ( hide ) Transformer Types Amorphous metal transformer Austin transformer Autotransformer Buck -- boost transformer Capacitor voltage transformer Current transformer Distribution transformer Delta - wye transformer Energy efficient transformer Flyback transformer Grounding transformer Instrument transformer Isolation transformer Dry Isolation transformer Linear variable differential transformer Modulation transformer Neon - sign transformer Padmount transformer Paraformer Planar transformers Rotary transformer Rotary variable differential transformer Scott - T transformer Trigger transformer Variable - frequency transformer Zigzag transformer Coils Hybrid coil Induction coil Oudin coil Polyphase coil Repeating coil Tesla coil Trembler coil Topics Agbioeletric Balun Buchholz relay Bushing Center tap Circle diagram Condition monitoring of transformers Copper loss Dissolved gas analysis Electrical insulation paper Growler High - leg delta Induction regulator Leakage inductance Magnet wire Metadyne Open - circuit test Polarity Polychlorinated biphenyl Prolec GE Quadrature booster Resolver Resonant inductive coupling Severity factor Short - circuit test Stacking factor Synchro Tap changer Toroidal inductors and transformers Transformer oil Transformer oil testing Transformer utilization factor Vector group Retrieved from `` https://en.wikipedia.org/w/index.php?title=Transformer_types&oldid=838140333 '' Categories : Electric transformers Hidden categories : All articles with unsourced statements Articles with unsourced statements from January 2013 Articles needing additional references from January 2013 All articles needing additional references Talk Contents About Wikipedia हिन्दी Edit links This page was last edited on 25 April 2018 , at 05 : 06 . 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Question: two examples where low voltage transformers are used