document_title: Minor League Baseball

question_text: what is the order of minor league baseball

question_tokens: what is the order of minor league baseball

text: Minor League Baseball

text: History[edit]

text: The earliest professional baseball association, the National Association of 1871 to 1875, comprised all fully professional teams. This system proved unworkable, however, as there was no way to ensure competitive balance, and financially unsound clubs often failed in midseason. This problem was solved in 1876 with the formation of the National League, with a limited membership which excluded less competitive and financially weaker teams. Professional clubs outside the National League responded by forming regional associations of their own. There was a series of ad hoc groupings, such as the New England Association of 1877 and the Eastern Championship Association of 1881. These were loose groups of independent clubs which agreed to play a series of games for a championship pennant.

text: The first minor league is traditionally considered to be the Northwestern League of 1883 to 1884. Unlike the earlier minor associations, it was conceived as a permanent organization. It also, along with the National League and the American Association, was a party to the National Agreement of 1883. Included in this was the agreement to respect the reserve lists of clubs in each league. Teams in the National League and the American Association could only reserve players who had been paid at least $1000. Northwest League teams could reserve players paid merely $750, implicitly establishing the division into major and minor leagues. Over the next two decades, more minor leagues signed various versions of the National Agreement. Eventually, the minor leagues joined together to negotiate jointly.

text: In the late 1890s, the Western League run by the fiery Ban Johnson decided to challenge the National League's position. In 1900, he changed the name of the league to the American League and vowed to make deals to sign contracts with players who were dissatisfied with the pay and terms of their deals with the National League. This led to a nasty turf war that heated up in 1901 enough to concern Patrick T. Powers, president of the Eastern League, and many other minor league owners about the conflict potentially affecting their organizations. Representatives of the different minor leagues met at the Leland Hotel in Chicago on September 5, 1901. In response to the National–American battle, they agreed to form the National Association of Professional Baseball Leagues, called the NAPBL, or NA for short. (The NA uses the name Minor League Baseball today.) The purpose of the NA at the time was to maintain the independence of the leagues involved. Several did not sign the agreement and continued to work independently. Powers was made the first president of the NAPBL, whose offices were established in Auburn, New York.

text: In 1903, the conflict between the American and National Leagues ended in the National Agreement of 1903.[2] The NAPBL became involved in the later stages of the negotiations to develop rules for the acquisition of players from their leagues by the National and the American. The 1903 agreement ensured that teams would be compensated for the players that they had taken the time and effort to scout and develop, and no NA team was required to sell their players, although most did because the cash was an important source of revenue for most teams. The NA leagues were still fiercely independent, and the term "minor" was seldom used in reference to them, save by the major-market sports writers. News did not travel far in the days before television and radio, so, while the leagues often bristled at the major market writers descriptions, they viewed themselves as independent sports businesses. Many baseball writers of that time regarded the greatest players of the minor leagues, such as Buzz Arlett, Jigger Statz, Ike Boone, Buddy Ryan, Earl Rapp and Frank Shellenback, as comparable to major league players. Leagues in the NA would not be truly called minor until Branch Rickey developed the first modern farm system in the 1930s. The Commissioner of Baseball, Kenesaw Mountain Landis fought Rickey's scheme, but, ultimately, the Great Depression drove teams to establish systems like Rickey's to ensure a steady supply of players, as many NA and independent teams could not afford to keep their doors open without the patronage of major league baseball. The leagues of the NA became subordinate to the major leagues, creating the first minor leagues. Other than the Pacific Coast League, which under its president Pants Rowland tried to become a third major league in the Western states, the other leagues maintained autonomy in name only, being totally economically dependent upon the American and National leagues.

text: In 1922, the United States Supreme Court decision Federal Baseball Club v. National League (259 U.S. 200), which grants baseball a special immunity from antitrust laws, had a major effect on the minor leagues. The special immunity meant that the American and National leagues could dictate terms under which every independent league did business. By 1925, major league baseball established a flat-fee purchase amount of $5,000 for the contract of any player from an NA league team. This power was leveled primarily at the Baltimore Orioles, then a Triple-A team that had dominated the minors with stars.

text: Current system[edit]

text: Under most circumstances, minor league teams are not owned by major league clubs, but have affiliation contracts with them. A small number of minor league clubs are directly owned by major league clubs, but these are rare. Major league Rule 56 governs the standard terms of a Player Development Contract (PDC) which is the standard agreement of association between a minor league team and its major league affiliate. Generally, the parent major league club pays the salaries and benefits of uniformed personnel (players and coaches) and bats and balls, while the minor league club pays for in-season travel and other operational expenses.[3]

text: Minor league teams often change their affiliation with major league clubs for a variety of reasons. Sometimes major or minor League clubs wish to affiliate with a partner that is geographically closer. In recent years, some MLB clubs have attempted to place as many affiliated teams within their blackout area as possible, in order to make scouting and player transfers more convenient and to take advantage of the existing fan base when interest in the parent team builds support for the minor league affiliate and early fan interest in developing minor league players reinforces support for the parent team as "local players" reach the majors. Sometimes a minor league club wishes to improve the caliber of players its major league affiliate sends to play there. Sometimes a major league club wishes to improve the facility where it will send its developing players. In even-numbered years, any major or minor league club with an expiring PDC may notify Major League Baseball or Minor League Baseball, respectively, of its desire to explore a re-affiliation with a different PDC partner. The Major League Baseball and Minor League Baseball offices then send a list of the corresponding major and minor league clubs seeking new affiliations, and there is a limited period of time in September within which clubs may agree upon new PDCs. If any are left over after this process, the Major League Baseball and Minor League Baseball offices are empowered to assign major and minor league clubs to each other.

text: Going into the 2010 season, the longest continuous link between major league and minor league clubs was the link between the Orioles and their Rookie-level Appalachian League affiliate, the Bluefield Orioles. The teams were affiliated for 53 years, from 1958 through 2010. Baltimore ended the PDC after the 2010 season. At the start of the 2011 season, the longest continuous affiliations were two 45-year links: between the Philadelphia Phillies and their Double-A Eastern League affiliate, the Reading Fightin Phils; and the one between the Detroit Tigers and their Class A-Advanced Florida State League affiliate, the Lakeland Flying Tigers. Both Reading and Lakeland are owned by their parent Major League clubs.

text: There are several baseball clubs that operate teams at multiple levels of the minor leagues; they are not required to affiliate all of their clubs to the same major league franchise. Bob Rich, Jr., for example, owns the Triple-A Buffalo Bisons and the short-season West Virginia Black Bears, the latter of which had been the Jamestown Jammers before the 2015 season. Even though the teams were located slightly more than 70 miles (110 km) apart before the Jammers' relocation, Rich has never affiliated the two teams with the same parent club.

text: The current minor league classification system divides leagues into one of five classes, those being Triple-A (AAA), Double-A (AA), Class A (Single-A or A), Class A Short Season, and Rookie. Furthermore, Class A is further subdivided into Class A and Class A-Advanced (often called Low-A and High-A, respectively), and Rookie is further subdivided into Rookie Advanced, Complex-based Rookie and international summer baseball. Under the rules governing the affiliated minor leagues (specifically Major League Baseball Rule 51), Class A Short Season is a separate classification from the other leagues bearing the "Class A" name, despite the similarity in name.

text: Triple-A[edit]

text: This classification currently includes two affiliated leagues: the International League and the Pacific Coast League, which feature teams from Eastern and Western United States respectively.[4] For most of the 20th century, it also contained the American Association, based in the Midwest, but that league disbanded, its clubs absorbed by the other two leagues, as part of a reorganization of the Triple-A level in 1997. The Mexican League is also classified as a Triple-A league, though its clubs do not have PDCs with Major League clubs.

text: Both young players and veterans play for Triple-A teams. Teams usually hold many of the remaining 15 players of the 40-man major league roster whom the major league club has chosen not to play at the major league level. Players at Triple-A on the 40-man roster can be invited to come up to the major league club once the major league roster expands on September 1, although teams usually wait until their affiliates' playoff runs are over, should they qualify. For teams in contention for a pennant, it gives them fresh players. For those not in contention, it gives them an opportunity to evaluate their second-tier players against major-league competition.[5] Some Triple-A players are "career minor leaguers", former prospects whose skill growth has halted and are not likely to be ready for MLB action unless as a temporary replacement.[6]

text: Unlike at other levels of competition, the two affiliated Triple-A leagues meet each summer in the Triple-A All-Star Game, first played in 1988. Each league fields a team composed of the top players in their respective leagues as voted on by fans, the media, and each club's field manager and general manager.[7] In another instance of interleague play, the annual Triple-A Baseball National Championship Game has been held since 2006 to serve as a single championship game between the champions of the International League and Pacific Coast League to determine an overall champion of Triple-A baseball.[8]

text: Double-A[edit]

text: There are currently three leagues in this classification: Eastern League, Southern League, and the Texas League.[4] Some players jump to the majors from this level, as many of the top prospects are put here to play against each other rather than against minor and major league veterans in Triple-A.[6] A small handful of players might be placed here to start, usually veterans from foreign leagues with more experience in professional baseball. The expectation is usually that these players will be in the majors by the end of the season, as their salaries tend to be higher than those of most prospects.

text: Unlike the major league and the Triple-A level, two of the three Double-A leagues play a split season, the Eastern League being the exception. One team may clinch a spot in the playoffs by winning the division in first half of the season. The teams' records are then cleared and another team will also clinch a playoff slot during the second half. Wild cards are used to fill out the remaining teams. Usually, four teams qualify for the league playoffs. This system is used at the Class A level as well.

text: Class A-Advanced[edit]

text: One level below Double-A, the California League, Carolina League, and the Florida State League play at the Class A-Advanced level, also known as "Class A+" or "High A".[4] This is often a second or third promotion for a minor league player, although a few high first-round draftees, particularly those with college experience, begin at this level. These leagues play a complete season like Triple-A and Double-A, from April through early September. Many of the teams in the Florida State League are owned by major league parent clubs and use their spring training complexes. The class consists of 30 teams from around the United States, from San Jose to Tampa.

text: Class A[edit]

text: Slightly below Class A-Advanced are the full season Class A leagues, the South Atlantic League and Midwest League.[4] These leagues are a mix of players moving up from the Short Season and Rookie leagues, as well as the occasional experienced first-year player. These leagues play a full, 140 game schedule, which runs from the first week of April through the first week of September.

text: Short season leagues[edit]

text: Short season leagues, as the name implies, play a shortened season of 76 games, starting in mid-June and ending in early September, with only a few off-days during the season. The late start of the season is designed to allow college players to complete their college seasons in the spring, then be drafted, signed, and immediately placed in a competitive league (The MLB First Year Player Draft begins on the first Monday in June).

text: Players in short season leagues are a mixture of newly signed draftees who are considered more advanced than other draftees, and second-year pros who were not ready or for whom there was not space at a higher level to move up. Second-year pros are assigned to "extended spring training" in Florida or Arizona during April and May before reporting to their short season leagues.

text: Of the 30 major league clubs, 13 field teams in Class A Short Season only, 8 clubs field their top short season teams in the Rookie Advanced leagues, and 9 clubs have affiliates at both levels.

text: Class A Short Season[edit]

text: Class A Short Season, despite the name, is a separate classification from Class A. Class A Short Season teams are slightly more limited than Class A teams with respect to player age and years of experience in professional baseball. There are two short season leagues, the New York–Penn League and Northwest League.

text: Rookie Advanced[edit]

text: The Appalachian League and Pioneer League are known as "Rookie Advanced" leagues. The players in these leagues are thought to be further along in their development than players in the pure Rookie leagues, and hence games are more competitive. Teams in these leagues sell concessions and charge admission.

text: Rookie[edit]

text: Leagues in the Rookie classification play a shortened season, similar to, but slightly shorter than, the short season leagues, starting in mid-June and ending in late August or early September. This lowest level of minor league baseball consists of two domestic leagues, the Arizona League and Gulf Coast League, and one foreign-based league, the Dominican Summer League.[4]

text: The domestic Rookie leagues play a 60-game schedule, and are usually called "complex leagues" because games are played at their parent clubs' spring training complexes. Rosters comprise newly drafted players who are not ready for a higher level of play. These leagues are intended almost exclusively to allow players to hone their skills; no admission is charged and no concessions are sold.

text: Rehabilitation assignments[edit]

text: Players on the disabled list (DL) can be sent to the minor leagues to aid in rehabilitation following an injury, typically for one or two weeks. Players are often sent to minor league clubs based on geography and facilities, not necessarily by class for these reassignments.

text: Curt Schilling's recovery from an ankle injury in 2005 saw him rehab in Pawtucket, Rhode Island at the Triple-A Pawtucket Red Sox, very close to the home club in Boston. The Cincinnati Reds often send players to their Class A affiliate, the Dayton Dragons, for rehab assignments. Despite Dayton's status as Low Class A, Dayton is a short, 50-mile drive away from the Reds' Great American Ball Park.

text: Minnesota Twins superstar Joe Mauer, who missed most of the first two months of the 2011 season due to a difficult recovery from arthroscopic knee surgery after the 2010 season, reported to Minnesota's Class A-Advanced Florida State League team, the Fort Myers Miracle, which is based in their well-equipped Spring Training facility in Fort Myers. In addition, the Miracle manager at the time was Mauer's older brother Jake. The Twins would later send Joe Mauer and pitcher Ricky Nolasco to rehab with the club's Low-A affiliate located across the Minnesota-Iowa border in Cedar Rapids.[9]

text: Mike Trout's first rehab assignment of his career, in July 2017, was with the Inland Empire 66ers of San Bernardino, California, the Class A-Advanced affiliate of the Los Angeles Angels. This allowed Trout to stay closer to the Angels compared to the team's Triple-A affiliate, the Salt Lake Bees.[10]

text: Reorganization of 1963[edit]

text: The current minor league structure is largely based on a significant reorganization that occurred before the 1963 season, which was caused by the club and league contraction of the 1950s and early 1960s. In 1949, the peak of the post-World War II minor league baseball boom, 438 teams in 59 leagues were members of the National Association of Professional Baseball Leagues. By the end of 1963, only 15 leagues survived in the United States and Canada.[11]

text: Previous structure (1946–1962)[edit]

text: Before 1946, the minors' highest level was labeled Double-A. In 1946, the Triple-A classification was created and the three Double-A circuits (the Pacific Coast and International leagues, and the American Association) were automatically reclassified Triple-A. The Class A1 level, two rungs below the Majors and comprising the Texas League and the Southern Association, was then renamed Double-A.

text: Prior to 1963, the Class A level was a higher-rung classification. In 1946, Class A consisted of the Eastern League and the original South Atlantic or "Sally" League, and it would soon include the Western League (1947–1958), the Central League (1948–1951), and the Western International League (1952–1954). The WIL became the Class B Northwest League in 1955, and the Western and Central loops folded. But postwar Class A cities included communities such as Denver, in Major League Baseball since 1993, as well as Vancouver, Omaha, Colorado Springs, Scranton and Allentown, which would establish themselves as Triple-A venues.

text: The lower levels of the minors were ranked Classes B through D in descending order. With the exception of the 1952–1957 Open Classification experiment for the Pacific Coast League, this structure would remain intact through 1962. (see Defunct levels, below)

text: The 1963 classification realignment[edit]

text: After the 1962 season, the Triple-A American Association disbanded and the surviving International and Pacific Coast leagues absorbed the four remaining American Association franchises. Meanwhile, at the Double-A level and below there were even more significant changes:

text:
The two existing Class A leagues—the Eastern and South Atlantic—were upgraded to Double-A, joining the Texas League and the Mexican League, then Double-A, as members of this classification. This move was caused by the disbanding of the Southern Association after 1961, leaving the six-team Texas League as the only U.S.-based Double-A circuit in 1962. (The Mexican League, although a formal member of minor league baseball, was not affiliated with any Major League teams.) In addition, many Major League parent teams had frequently treated the pre-1963 Eastern and South Atlantic leagues as de facto Double-A circuits, one step (rather than two) below Triple-A.
The Class B Carolina League and Northwest League, the Class C California League, Pioneer League and Northern League, and the Class D Florida State League, Georgia–Florida League, Midwest League, New York–Penn League, and Western Carolinas League were all designated Class A (or Single-A) leagues. (The unaffiliated Mexican Central League of 1960–1978, ranked Class C in 1962, also was upgraded to Class A.)
The Class D Appalachian League, then the only "short-season" circuit, was given a new designation as a "Rookie" league.

text: As part of the 1963 reorganization, Major League clubs increased their commitments to affiliate with minor league teams through Player Development Contracts, outright ownerships, or shared affiliations and co-op arrangements.[11]

text: Further changes after 1963[edit]

text:
Triple-A: The American Association was revived as a Triple-A league in 1969 and flourished with the minor league baseball boom of the 1980s and 1990s. However, all of its teams were again absorbed into the International and Pacific Coast leagues in 1998 as part of a sweeping reorganization of the minors' top classification. The American Association and the International League also played an interlocking schedule during the late 1980s as part of the Triple-A Alliance. The Mexican League was upgraded from Double-A to Triple-A in 1967.
Double-A: In 1964, the South Atlantic League changed its name to its current identity, the Southern League. Because of continued contraction (and Major League expansion) that left each circuit with only seven teams, the Texas and Southern leagues merged into an umbrella circuit, the Dixie Association, in 1971. The arrangement lasted only for that season and the records and history of the Texas and Southern loops were kept distinct. In 1972, each league added an eighth team, rebalancing their schedules. They resumed their former, separate identities, and returned to prosperity with the revival of minor league baseball that began in the 1980s.
Class A: In 1965, the Class A–Short Season designation was created, and the Northern and Northwest loops moved from "full season" Class A into the new classification (with the New York–Penn League following in 1967). The Georgia–Florida League disbanded after the 1963 season, while the Northern League played its last year in official minor league baseball in 1971. In 1980, the Western Carolinas League changed its identity to become the modern incarnation of the South Atlantic League.
Rookie: In 1964, the Pioneer League stepped down from Class A to Rookie league status, and the first "complex-based" leagues, the Sarasota Rookie League and the Cocoa Rookie League, made their debuts. The Sarasota Rookie League underwent a name change to the Florida Rookie League in 1965 before becoming the modern Gulf Coast League the next season. The Cocoa Rookie League lasted only one season, but the Florida East Coast League of 1972 was based in the same region of the state. In 1989, an Arizona-based counterpart to the Gulf Coast League, the Arizona League, made its debut in minor league baseball, and it continues to operate as a Rookie-level league for MLB teams with spring training facilities based in that state.
Failed start-up leagues: During the 1970s, three "official" minor leagues attempted unsuccessfully to revive unaffiliated baseball within the organized baseball structure. These were the Class A Gulf States League (1976) and Lone Star League (1977), and the Triple-A Inter–American League (1979). None lasted more than a full season.

text: Defunct levels[edit]

text: Open[edit]

text: The Pacific Coast League, from 1952–1957, was the only minor league to obtain open classification. At this time, the major leagues only extended as far west as St. Louis and as far south as Washington, D.C. This classification severely restricted the rights of the major leagues to draft players out of the PCL, and at the time it seemed like the PCL would eventually become a third major league. The PCL would revert to Triple-A classification in 1958 due to increasing television coverage of major league games and in light of the Dodgers and Giants moving to Los Angeles and San Francisco, respectively. The open classification no longer exists in the major league rules.

text: Class A1[edit]

text: The forerunner to the modern Double-A classification, the A1 level existed from 1936 through 1945. In 1936, two Class A circuits, the Texas League and the Southern Association, were upgraded to Class A1 to signify their continued status as one step below the highest classification, then Double-A, yet a notch above their former Class A peers, the New York–Pennsylvania League and Western League. Ten years later, after World War II, with the minor leagues poised for unprecedented growth, classification terminology was changed. Beginning in 1946, the three Double-A leagues (the American Association and International and Pacific Coast leagues) joined a new classification, Triple-A, and the Class A1 level became known as Double-A.

text: Class B, C and D[edit]

text: Until 1963, there were also Class B, C, and D leagues (and, for half a season, one E league). The Class D of that period would be equivalent to the Rookie level today. The other class designations disappeared because leagues of that level could not sustain operation during a large downturn in the financial fortunes of minor league baseball in the 1950s and 1960s caused by the rise of television broadcasts of major league sports across broad regions of the country. The impact of the Korean War in 1950 caused a player shortage in most cities in class D and C. The Class E level existed briefly in 1943 in the form of the Twin Ports League. It folded July 13 after six weeks of operation.

text: Players[edit]

text: Only 25 of the players on a Major League Baseball team's 40-man major league reserve list may be active for the major league club, with two exceptions. One minor exception is that when a team is scheduled to play a day-night doubleheader, it is allowed to carry 26 players on the active roster for that day only. The more significant exception is that from September 1 to the end of the regular season, teams are allowed to expand their game-day rosters to 40 players. The remaining 15 players are generally either on the disabled list or play at some level of the minor leagues (usually at the Triple-A or Double-A level). Players on the 40-man reserve list are eligible for membership in the Major League Baseball Players Association. The minor league players work at the lower end of major league pay scales and are covered by all rules and player agreements of the players association. Minor league players not on the 40-man reserve list are under contract to their respective parent Major League Baseball clubs but have no union. They generally work for far less pay as they develop their skills and work their way up the ladder toward the major leagues.[12] Many players have signing bonuses and other additional compensation that can run into the millions of dollars, although that is generally reserved for early round draft picks.

text: A major league team's Director of Player Development determines where a given player will be placed in the farm system, in coordination with the coaches and managers who evaluate their talent. At the end of spring training, players both from the spring major camp and minor league winter camp are placed by the major league club on the roster of a minor league team. The Director of Player Development and the general manager usually determine the initial assignments for new draftees, who typically begin playing professionally in June after they have been signed to contracts. The farm system is ever-changing, and evaluation of players is a constantly ongoing process. The Director of Player Development and his managers meet or teleconference regularly to discuss how players are performing at each level. Personal development, injuries, and high levels of achievement by players in the classes below all steer a player's movement up and down in the class system.

text: Players will play for the team to which they are assigned for the duration of that season unless they are "called up" (promoted to a higher level), "sent down" (demoted to a lower-class team in the major league club's farm system), or "released" from the farm system entirely. A release from minor-league level used to spell the end of a minor league player's career. In more modern times, released players often sign with independent baseball clubs, which are scouted heavily by major league organizations. Many players get a second or third look from the major league scouts if they turn their career around in the independent leagues.

text: Even though minor league players are paid considerably less than their major league counterparts, they are nevertheless paid for their services and are thus considered professional athletes. Minor league salaries vary based on class level and length of season; however, the majority of players make less than $10,000 per season.[13] Baseball cards refer to "pro record" and "pro seasons" as including both major and minor leagues. For this reason, minor league players generally consider it an insult when someone asks when they're going to "get to the pros". More accurately, a player's aim is to reach "The Show" or the "big leagues."

text: Umpires[edit]

text: Umpires at the minor league level are overseen by Minor League Baseball Umpire Development, which is responsible for the training, evaluation, and recommendation for promotion and retention or release of the umpires.[14]

text: The umpires are evaluated eight times a season by the staff of the MiLB Umpire Development, and receive a ranking at mid-season and the end of each year. Based on performance during the year, an umpire may advance in classification when a position opens in-season or during the off-season. Umpire Development holds an annual evaluation course every year in March to evaluate rookie umpires. Participants are normally the best students from the two professional umpire schools (one owned and operated by the same entity). The top students who pass the evaluation course are recommended for the first openings in the Rookie and short season leagues.[15]

text: Any student who wants to work as an umpire must attend a professional umpire training school. The MiLB recognizes two schools for training prospective professional umpires, the Harry Wendelstedt Umpire School and Minor League Baseball Umpire Training Academy, both located in Florida. The Minor League Baseball Umpire Training Academy is owned and operated by Minor League Baseball Umpire Development (MiLBUD), while Wendelstedt is independently owned by MLB Umpire Hunter Wendelstedt. The classes for each school are held for five weeks in January and February. The instructors at these schools are former or present major or minor league umpires. Simply attending one of these schools, however, does not guarantee that the candidate will also be recommended either to the evaluation course or to the openings in the Rookie or short season leagues. Generally, less than 20% of umpire school students move on to the Rookie Evaluation Course.[16]

text: Before the umpire development program was created, the Minor League presidents would recruit umpires directly from the schools. Umpires were then "sold" from league to league by word of mouth through the various league presidents.[17]

text: The umpire development program first started in 1964, when it was decided that a method of recruitment, training and development for umpires of both major and minor leagues was needed. The Umpire Development Program was founded at Baseball's 1964 Winter Meetings in Houston, and it began operating the next year. The program aimed to recruit more athletic, energetic and dedicated individuals who would also have high morals and integrity standards. In 1968, it was decided that the program needed its own umpire training course which would be held each year. The first "Umpire Specialization Course" was held in St. Petersburg, Florida the following year.[18]

text: Presently, the candidates for a job in professional umpiring must meet several requirements in order to be considered. An applicant must have a high school diploma or a G.E.D., must be athletic, and also must have 20/20 vision, though they are permitted to wear glasses or contact lenses.[19] They must also have good communication skills, good reflexes and coordination, and must have trained at one of the two professional umpire schools.

text: On June 21, 2016, the Gulf Coast League hired Jen Pawol, the first female umpire in Minor League Baseball since 2007.[20]

text: Presidents of Minor League Baseball[edit]

text:
Patrick T. Powers, 1901–1909
Michael H. Sexton, 1909–1931
William G. Bramham, 1932–1946
George Trautman, 1947–1963
Phil Piton, 1964–1971
Hank Peters, 1972–1975
Bobby Bragan, 1976–1978
John H. Johnson, 1979–1988
Sal Artiaga, 1988–1991
Mike Moore, 1991–2007
Pat O'Conner, 2008–present

text: Television and radio[edit]

text: Minor League Baseball has a national television contract with CBS Sports Network, which airs 10–15 games on Thursday nights. The arrangement began in 2014 and will continue through the 2015 season.[21] For the 2015 season, select MiLB games will be featured on the American Sports Network.[22] Also, many individual teams have contracts with local over-the-air channels. Games are also occasionally simulcast on MLB Network.

text: MiLB.TV[edit]

text: MiLB.TV is the minor leagues' official online video streaming service, in the vein of Major League Baseball's MLB.tv. The service currently offers every Triple-A game and select games from the other classifications.

text: Radio[edit]

text: Nearly every minor-league team has its own local radio contract, though unlike their major-league counterparts, these generally consist of only one or two individual stations. Minor League Baseball currently has an arrangement with TuneIn to provide free audio streams of virtually every game.[23]

text: Independent baseball[edit]

text: Independent leagues are those professional leagues in the United States and Canada not under the purview of organized Minor League Baseball and the Commissioner of Baseball. Independent baseball existed in the early 20th century and has become prominent again since 1993.[24]

text: Leagues operated mostly autonomously before 1902, when the majority joined the NAPBL. From then until 1915, a total of eight new and existing leagues remained independent. Most joined the National Association after one season of independence. Notable exceptions were the California League, which was independent in 1902 and from 1907–1909, the United States Baseball League, which folded during its independent 1912 season, and the Colonial League, a National Association Member that went independent in 1915 and then folded.[25] Another independent league, the Federal League, played at a level considered major league from 1914–1915.

text: Few independent leagues existed between 1915 and 1993. Major exceptions included the Carolina League and the Quebec-based Provincial League. The Carolina League, based in the North Carolina Piedmont region, gained a reputation as a notorious "outlaw league" during its existence from 1936–1938.[26] The Provincial League had six teams across Quebec and was independent from 1948–1949. Similarly to early 20th-century independent leagues, it joined the National Association in 1950, playing for six more years.[25][27]

text: Independent leagues saw new growth after 1992, after the new Professional Baseball Agreement in organized baseball instituted more stringent revenue and stadium requirements on members.[28] Over the next eight years, at least 16 independent leagues formed, of which six existed in 2002.[25] As of 2016, seven independent leagues are in operation in the U.S. and Canada, compared to 19 in organized Minor League Baseball.

text: List of leagues[edit]

text:
International League
Pacific Coast League
Mexican League[29]

text:
Eastern League
Southern League
Texas League

text:
California League
Carolina League
Florida State League

text:
Midwest League
South Atlantic League

text:
New York–Penn League
Northwest League

text:
Pioneer League
Appalachian League

text:
Arizona League
Gulf Coast League
Dominican Summer League

text:
Arizona Fall League
Australian Baseball League
Colombian Professional Baseball League
Dominican Professional Baseball League
Mexican Pacific League
Puerto Rico Baseball League
Venezuelan Professional Baseball League

text:
American Association
Atlantic League
Can-Am League
Empire Professional Baseball League
Frontier League
Pacific Association
Pecos League
United Shore League

text: Major league affiliations[edit]

text:
Table key

Triple-A
Double-A
Class A-Advanced
Class A
Class A Short Season
Rookie Advanced

International League
Eastern League
Carolina League
South Atlantic League
New York-Penn League
Appalachian League

Pacific Coast League
Texas League
California League
Midwest League
Northwest League
Pioneer League

—

Southern League
Florida State League

—

—

—

text:
Division
Team
Triple-A
Double-A
Class A-Advanced
Class A
Class A Short Season
Rookie Advanced

American League

East
Baltimore Orioles
Norfolk Tides
Bowie Baysox
Frederick Keys
Delmarva Shorebirds
Aberdeen IronBirds

—

Boston Red Sox
Pawtucket Red Sox
Portland Sea Dogs
Salem Red Sox
Greenville Drive
Lowell Spinners

—

New York Yankees
Scranton/Wilkes-Barre RailRiders
Trenton Thunder
Tampa Yankees
Charleston RiverDogs
Staten Island Yankees
Pulaski Yankees

Tampa Bay Rays
Durham Bulls
Montgomery Biscuits
Charlotte Stone Crabs
Bowling Green Hot Rods
Hudson Valley Renegades
Princeton Rays

Toronto Blue Jays
Buffalo Bisons
New Hampshire Fisher Cats
Dunedin Blue Jays
Lansing Lugnuts
Vancouver Canadians
Bluefield Blue Jays

Central
Chicago White Sox
Charlotte Knights
Birmingham Barons
Winston-Salem Dash
Kannapolis Intimidators

—

Great Falls Voyagers

Cleveland Indians
Columbus Clippers
Akron RubberDucks
Lynchburg Hillcats
Lake County Captains
Mahoning Valley Scrappers

—

Detroit Tigers
Toledo Mud Hens
Erie SeaWolves
Lakeland Flying Tigers
West Michigan Whitecaps
Connecticut Tigers

—

Kansas City Royals
Omaha Storm Chasers
Northwest Arkansas Naturals
Wilmington Blue Rocks
Lexington Legends

—

Burlington Royals
Idaho Falls Chukars

Minnesota Twins
Rochester Red Wings
Chattanooga Lookouts
Fort Myers Miracle
Cedar Rapids Kernels

—

Elizabethton Twins

West
Houston Astros
Fresno Grizzlies
Corpus Christi Hooks
Buies Creek Astros
Quad Cities River Bandits
Tri-City ValleyCats

—

Los Angeles Angels
Salt Lake Bees
Mobile BayBears
Inland Empire 66ers
Burlington Bees

—

Orem Owlz

Oakland Athletics
Nashville Sounds
Midland RockHounds
Stockton Ports
Beloit Snappers
Vermont Lake Monsters

—

Seattle Mariners
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Modesto Nuts
Clinton LumberKings
Everett AquaSox

—

Texas Rangers
Round Rock Express
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Down East Wood Ducks
Hickory Crawdads
Spokane Indians

—

National League

East
Atlanta Braves
Gwinnett Braves
Mississippi Braves
Florida Fire Frogs
Rome Braves

—

Danville Braves

Miami Marlins
New Orleans Baby Cakes
Jacksonville Jumbo Shrimp
Jupiter Hammerheads
Greensboro Grasshoppers
Batavia Muckdogs

—

New York Mets
Las Vegas 51s
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St. Lucie Mets
Columbia Fireflies
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Kingsport Mets

Philadelphia Phillies
Lehigh Valley IronPigs
Reading Fightin' Phils
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Lakewood BlueClaws
Williamsport Crosscutters

—

Washington Nationals
Syracuse Chiefs
Harrisburg Senators
Potomac Nationals
Hagerstown Suns
Auburn Doubledays

—

Central
Chicago Cubs
Iowa Cubs
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Myrtle Beach Pelicans
South Bend Cubs
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—

Cincinnati Reds
Louisville Bats
Pensacola Blue Wahoos
Daytona Tortugas
Dayton Dragons

—

Billings Mustangs

Milwaukee Brewers
Colorado Springs Sky Sox
Biloxi Shuckers
Carolina Mudcats
Wisconsin Timber Rattlers

—

Helena Brewers

Pittsburgh Pirates
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Bristol Pirates

St. Louis Cardinals
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State College Spikes
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West
Arizona Diamondbacks
Reno Aces
Jackson Generals
Visalia Rawhide
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Hillsboro Hops
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Colorado Rockies
Albuquerque Isotopes
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Los Angeles Dodgers
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Great Lakes Loons

—

Ogden Raptors

San Diego Padres
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Fort Wayne TinCaps
Tri-City Dust Devils

—

San Francisco Giants
Sacramento River Cats
Richmond Flying Squirrels
San Jose Giants
Augusta GreenJackets
Salem-Keizer Volcanoes

—

text: Team rosters[edit]

text: Awards[edit]

text: MiLBY Awards[edit]

text: The Minor League Baseball Yearly (MiLBY) Awards (formerly "This Year in Minor League Baseball Awards") are given in nine categories. In five categories (Best Starter, Best Hitter, Best Reliever, Best Game, and Best Team), winners are selected in each of the five levels of minor-league baseball (Triple-A, Double-A, Class A-Advanced, Class A, and Class A Short Season). In three categories (Play of the Year, Moment of the Year, and Homer of the Year), one overall winner is chosen for all of minor-league baseball. In the remaining category (Promo of the Year), there are overall winners in each of five subcategories: Best Promotion (of all types), Best Theme Night, Best Giveaway, Best Celebrity Appearance, and Best Miscellaneous Promotion.

text: Other player awards[edit]

text:
MiLB J.G. Taylor Spink Award (Topps/Minor League Player of the Year)[30][31]
MiLB George M. Trautman Awards (Topps Player of the Year) (in each of 16 domestic minor leagues)[32]
MiLB Joe Bauman Home Run Award[33]

text: Major awards[edit]

text:
John H. Johnson President's Award (1974) – given each year, MiLB's top award recognizes "the complete baseball franchise—based on franchise stability, contributions to league stability, contributions to baseball in the community, and promotion of the baseball industry."[34][35]
Rawlings Woman Executive of the Year (1976) – given each year to a woman in MiLB for exceptional contributions to her club, her league, or baseball.[34][36]
Warren Giles Award (1984) – given each year to a league president for outstanding service.[34][36][37]
King of Baseball (1951) – given annually in recognition of longtime dedication and service to professional baseball.[34]
Larry MacPhail Award (1966) – given annually in recognition of team promotions.[34][38]
Sheldon "Chief" Bender Award (2008) – given to a person with distinguished service who has been instrumental in player development.[34]
Mike Coolbaugh Award (2008) – given to someone who has shown an outstanding baseball work ethic, knowledge of the game, and skill in mentoring young players on the field.[34]

text: Top 100 teams[edit]

text: During its centennial celebration in 2001, Minor League Baseball compiled a list of the 100 best minor-league baseball teams of the century.[39]


document_title: Wind turbine design

question_text: do wind turbines produce ac or dc power

question_tokens: do wind turbines produce ac or dc power

root

text: Wind turbine design

text: Aerodynamics[edit]

text: The shape and dimensions of the blades of the wind turbine are determined by the aerodynamic performance required to efficiently extract energy from the wind, and by the strength required to resist the forces on the blade.

tag: p

text: The aerodynamics of a horizontal-axis wind turbine are not straightforward. The air flow at the blades is not the same as the airflow far away from the turbine. The very nature of the way in which energy is extracted from the air also causes air to be deflected by the turbine. In addition the aerodynamics of a wind turbine at the rotor surface exhibit phenomena that are rarely seen in other aerodynamic fields.

text: In 1919, the physicist Albert Betz showed that for a hypothetical ideal wind-energy extraction machine, the fundamental laws of conservation of mass and energy allowed no more than 16/27 (59.3%) of the kinetic energy of the wind to be captured. This Betz' law limit can be approached by modern turbine designs which may reach 70 to 80% of this theoretical limit.

text: Power control[edit]

text: The speed at which  a wind turbine rotates must be controlled for efficient power generation and to keep the turbine components within designed speed and torque limits.  The centrifugal force on the spinning blades increases as the square of the rotation speed, which makes this structure sensitive to overspeed. Because the power of the wind increases as the cube of the wind speed, turbines have to be built to survive much higher wind loads (such as gusts of wind) than those from which they can practically generate power. Wind turbines have ways of reducing torque in high winds.

text: A wind turbine is designed to produce power over a range of wind speeds. The cut-in speed is around 3–4 m/s for most turbines, and cut-out at 25 m/s.[3] If the rated wind speed is exceeded the power has to be limited. There are various ways to achieve this.

text: A control system involves three basic elements: sensors to measure process variables, actuators to manipulate energy capture and component loading, and control algorithms to coordinate the actuators based on information gathered by the sensors.[4]

text: All wind turbines are designed for a maximum wind speed, called the survival speed, above which they will be damaged. The survival speed of commercial wind turbines is in the range of 40 m/s (144 km/h, 89 MPH) to 72 m/s (259 km/h, 161 MPH). The most common survival speed is 60 m/s (216 km/h, 134 MPH). Some have been designed to survive 80 metres per second (290 km/h; 180 mph).[5]

text: Stall[edit]

text: Stalling works by increasing the angle at which the relative wind strikes the blades (angle of attack), and it reduces the induced drag (drag associated with lift). Stalling is simple because it can be made to happen passively (it increases automatically when the winds speed up), but it increases the cross-section of the blade face-on to the wind, and thus the ordinary drag. A fully stalled turbine blade, when stopped, has the flat side of the blade facing directly into the wind.

text: A fixed-speed HAWT (Horizontal Axis Wind Turbine) inherently increases its angle of attack at higher wind speed as the blades speed up. A natural strategy, then, is to allow the blade to stall when the wind speed increases. This technique was successfully used on many early HAWTs. However, on some of these blade sets, it was observed that the degree of blade pitch tended to increase audible noise levels.

text: Vortex generators may be used to control the lift characteristics of the blade. The VGs are placed on the airfoil to enhance the lift if they are placed on the lower (flatter) surface or limit the maximum lift if placed on the upper (higher camber) surface.[6]

text: Furling[edit]

text: Furling works by decreasing the angle of attack, which reduces the induced drag from the lift of the rotor, as well as the cross-section. One major problem in designing wind turbines is getting the blades to stall or furl quickly enough should a gust of wind cause sudden acceleration. A fully furled turbine blade, when stopped, has the edge of the blade facing into the wind.

text: Loads can be reduced by making a structural system softer or more flexible.[4] This could be accomplished with downwind rotors or with curved blades that twist naturally to reduce angle of attack at higher wind speeds. These systems will be nonlinear and will couple the structure to the flow field - thus, design tools must evolve to model these nonlinearities.

text: Standard modern turbines all furl the blades in high winds. Since furling requires acting against the torque on the blade, it requires some form of pitch angle control, which is achieved with a slewing drive. This drive precisely angles the blade while withstanding high torque loads. In addition, many turbines use hydraulic systems. These systems are usually spring-loaded, so that if hydraulic power fails, the blades automatically furl. Other turbines use an electric servomotor for every rotor blade. They have a small battery-reserve in case of an electric-grid breakdown. Small wind turbines (under 50 kW) with variable-pitching generally use systems operated by centrifugal force, either by flyweights or geometric design, and employ no electric or hydraulic controls.

text: Fundamental gaps exist in pitch control, limiting the reduction of energy costs, according to a report from a coalition of researchers from universities, industry, and government, supported by the Atkinson Center for a Sustainable Future. Load reduction is currently focused on full-span blade pitch control, since individual pitch motors are the actuators currently available on commercial turbines. Significant load mitigation has been demonstrated in simulations for blades, tower, and drive train.  However, there is still research needed, the methods for realization of full-span blade pitch control need to be developed in order to increase energy capture and mitigate fatigue loads.

text: A control technique applied to the pitch angle is done by comparing the current active power of the engine with the value of active power at the rated engine speed (active power reference, Ps reference). Control of the pitch angle in this case is done with a PI controller controls. However, in order to have a realistic response to the control system of the pitch angle, the actuator uses the time constant Tservo, an integrator and limiters so as the pitch angle to be from 0° to 30° with a rate of change (± 10° per sec).

text: From the figure at the right, the reference pitch angle is compared with the actual pitch angle b and then the error is corrected by the actuator. The reference pitch angle, which comes from the PI controller, goes through a limiter. Restrictions on limits are very important to maintain the pitch angle in real term. Limiting the rate of change is very important especially during faults in the network. The importance is due to the fact that the controller decides how quickly it can reduce the aerodynamic energy to avoid acceleration during errors.[4]

text: Other controls[edit]

text: Generator torque[edit]

text: Modern large wind turbines are variable-speed machines. When the wind speed is below rated, generator torque is used to control the rotor speed in order to capture as much power as possible. The most power is captured when the tip speed ratio is held constant at its optimum value (typically 6 or 7). This means that as wind speed increases, rotor speed should increase proportionally. The difference between the aerodynamic torque captured by the blades and the applied generator torque controls the rotor speed. If the generator torque is lower, the rotor accelerates, and if the generator torque is higher, the rotor slows down. Below rated wind speed, the generator torque control is active while the blade pitch is typically held at the constant angle that captures the most power, fairly flat to the wind. Above rated wind speed, the generator torque is typically held constant while the blade pitch is active.

text: One technique to control a permanent magnet synchronous motor is Field Oriented Control. Field Oriented Control is a closed loop strategy composed of two current controllers (an inner loop and outer loop cascade design) necessary for controlling the torque, and one speed controller.

text: Constant torque angle control

text: In this control strategy the d axis current is kept zero, while the vector current is align with the q axis in order to maintain the torque angle equal with 90o. This is one of the most used control strategy because of the simplicity, by controlling only the Iqs current. So, now the electromagnetic torque equation of the permanent magnet synchronous generator is simply a linear equation depend on the Iqs current only.

text: So, the electromagnetic torque for Ids = 0 (we can achieve that with the d-axis controller) is now:

text: Te= 3/2 p (λpm Iqs + (Lds-Lqs) Ids Iqs )=  3/2 p λpm Iqs

text: So, the complete system of the machine side converter and the cascaded PI controller loops is given by the figure in the right. In that we have the control inputs, which are the duty rations mds and mqs, of the PWM-regulated converter. Also, we can see the control scheme for the wind turbine in the machine side and simultaneously how we keep the Ids zero (the electromagnetic torque equation is linear).

text: Yawing[edit]

text: Modern large wind turbines are typically actively controlled to face the wind direction measured by a wind vane situated on the back of the nacelle. By minimizing the yaw angle (the misalignment between wind and turbine pointing direction), the power output is maximized and non-symmetrical loads minimized. However, since the wind direction varies quickly the turbine will not strictly follow the direction and will have a small yaw angle on average. The power output losses can simply be approximated to fall with (cos(yaw angle))3. Particularly at low-to-medium wind speeds, yawing can make a significant reduction in turbine output, with wind direction variations of ±30° being quite common and long response times of the turbines to changes in wind direction. At high wind speeds, the wind direction is less variable.

text: Electrical braking[edit]

text: Braking of a small wind turbine can be done by dumping energy from the generator into a resistor bank, converting the kinetic energy of the turbine rotation into heat. This method is useful if the kinetic load on the generator is suddenly reduced or is too small to keep the turbine speed within its allowed limit.

text: Cyclically braking causes the blades to slow down, which increases the stalling effect, reducing the efficiency of the blades. This way, the turbine's rotation can be kept at a safe speed in faster winds while maintaining (nominal) power output. This method is usually not applied on large grid-connected wind turbines.

text: Mechanical braking[edit]

text: A mechanical drum brake or disk brake is used to stop turbine in emergency situation  such as extreme gust events or over speed. This brake is a secondary means to hold the turbine at rest for maintenance, with a rotor lock system as primary means. Such brakes are usually applied only after blade furling and electromagnetic braking have reduced the turbine speed generally 1 or 2 rotor RPM, as the mechanical brakes can create a fire inside the nacelle if used to stop the turbine from full speed. The load on the turbine increases if the brake is applied at rated RPM. Mechanical brakes are driven by hydraulic systems and are connected to main control box.

text: Turbine size[edit]

text: There are different size classes of wind turbines. The smallest having power production less than 10 kW are used in homes, farms and remote applications whereas intermediate wind turbines (10-250 kW ) are useful for village power, hybrid systems and distributed power.  The world's largest wind turbine, an 8-MW turbine located at the Burbo Bank Extension wind farm in Liverpool Bay, United Kingdom, was installed in 2016.[7] Utility-scale turbines (larger than one megawatt) are used in central station wind farms, distributed power and community wind.[8]

text: For a given survivable wind speed, the mass of a turbine is approximately proportional to the cube of its blade-length. Wind power intercepted by the turbine is proportional to the square of its blade-length.[9]  The maximum blade-length of a turbine is limited by both the strength, the stiffness of its material, and transportation considerations.

text: Labor and maintenance costs increase only gradually with increasing turbine size, so to minimize costs, wind farm turbines are basically limited by the strength of materials, and siting requirements.

text: Typical modern wind turbines have diameters of 40 to 90 metres (130 to 300 ft) and are rated between 500 kW and 2 MW. As of 2017 the most powerful turbine, the Vestas V-164, is rated at 9.5 MW and has a rotor diameter of 164m.[10]

text: Increasingly large wind turbines are being designed, manufacturers have not yet come close to the maximum size. The largest turbines are or will be as big as skyscrapers.[11]

text: Nacelle[edit]

text: The nacelle is housing the gearbox and generator connecting the tower and rotor. Sensors detect the wind speed and direction, and motors turn the nacelle into the wind to maximize output.

text: Gearbox[edit]

text: In conventional wind turbines, the blades spin a shaft that is connected through a gearbox to the generator. The gearbox converts the turning speed of the blades 15 to 20 rotations per minute for a large, one-megawatt turbine into the faster 1,800 revolutions per minute that the generator needs to generate electricity.[12] Analysts from GlobalData estimate that gearbox market grows from $3.2bn in 2006 to $6.9bn in 2011, and to $8.1bn by 2020. Market leaders were Winergy in 2011.[13] The use of magnetic gearboxes has also been explored as a way of reducing wind turbine maintenance costs.[14]

text: Generator[edit]

text: For large, commercial size horizontal-axis wind turbines, the electrical generator[15] is mounted in a nacelle at the top of a tower, behind the hub of the turbine rotor. Typically wind turbines generate electricity through asynchronous machines that are directly connected with the electricity grid. Usually the rotational speed of the wind turbine is slower than the equivalent rotation speed of the electrical network: typical rotation speeds for wind generators are 5–20 rpm while a directly connected machine will have an electrical speed between 750 and 3600 rpm. Therefore, a gearbox is inserted between the rotor hub and the generator. This also reduces the generator cost and weight. Commercial size generators have a rotor carrying a field winding so that a rotating magnetic field is produced inside a set of windings called the stator. While the rotating field winding consumes a fraction of a percent of the generator output, adjustment of the field current allows good control over the generator output voltage.

text: Older style wind generators rotate at a constant speed, to match power line frequency, which allowed the use of less costly induction generators.[citation needed] Newer wind turbines often turn at whatever speed generates electricity most efficiently. The varying output frequency and voltage can be matched to the fixed values of the grid using multiple technologies such as doubly fed induction generators or full-effect converters where the variable frequency current produced is converted to DC and then back to AC. Although such alternatives require costly equipment and cause power loss, the turbine can capture a significantly larger fraction of the wind energy. In some cases, especially when turbines are sited offshore, the DC energy will be transmitted from the turbine to a central (onshore) inverter for connection to the grid.

text: Gearless wind turbine[edit]

text: Gearless wind turbines (also called direct drive) get rid of the gearbox completely. Instead, the rotor shaft is attached directly to the generator, which spins at the same speed as the blades.

text: Advantages of PMDD generators over gear-based generators include increased efficiency, reduced noise, longer lifetime, high torque at low rpm, faster and precise positioning, and drive stiffness. [16] PMDD generators "eliminate the gear-speed increaser, which is susceptible to significant accumulated fatigue torque loading, related reliability issues, and maintenance costs."[17]

text: To make up for a direct drive generator's slower spinning rate, the diameter of the generator's rotor is increased so that it can contain more magnets to create the required frequency and power. Gearless wind turbines are often heavier than gear-based wind turbines. A study by the EU called "Reliawind"[18] based on the largest sample size of turbines has shown that the reliability of gearboxes is not the main problem in wind turbines. The reliability of direct drive turbines offshore is still not known, since the sample size is so small.

text: Experts from Technical University of Denmark estimate that a geared generator with permanent magnets may use 25 kg/MW of the rare-earth element Neodymium, while a gearless may use 250 kg/MW.[19]

text:
In December 2011, the US Department of Energy published a report stating critical shortage of rare-earth elements such as neodymium used in large quantities for permanent magnets in gearless wind turbines.[20] China produces more than 95% of rare-earth elements, while Hitachi holds more than 600 patents covering Neodymium magnets.
Direct-drive turbines require 600 kg of permanent magnet material per megawatt, which translates to several hundred kilograms of rare-earth content per megawatt, as neodymium content is estimated to be 31% of magnet weight. Hybrid drivetrains (intermediate between direct drive and traditional geared) use significantly less rare-earth materials.
While permanent magnet wind turbines only account for about 5% of the market outside of China, their market share inside of China is estimated at 25% or higher.
In 2011, demand for neodymium in wind turbines was estimated to be 1/5 of that in electric vehicles.[20]

text: Blades[edit]

text: Blade design[edit]

text:
The ratio between the speed of the blade tips and the speed of the wind is called tip speed ratio. High efficiency 3-blade-turbines have tip speed/wind speed ratios of 6 to 7.
Modern wind turbines are designed to spin at varying speeds (a consequence of their generator design, see above). Use of aluminum and composite materials in their blades has contributed to low rotational inertia, which means that newer wind turbines can accelerate quickly if the winds pick up, keeping the tip speed ratio more nearly constant. Operating closer to their optimal tip speed ratio during energetic gusts of wind allows wind turbines to improve energy capture from sudden gusts that are typical in urban settings.

text: In contrast, older style wind turbines were designed with heavier steel blades, which have higher inertia, and rotated at speeds governed by the AC frequency of the power lines. The high inertia buffered the changes in rotation speed and thus made power output more stable.

text:
It is generally understood that noise increases with higher blade tip speeds. To increase tip speed without increasing noise would allow reduction the torque into the gearbox and generator and reduce overall structural loads, thereby reducing cost.[4]
The reduction of noise is linked to the detailed aerodynamics of the blades, especially factors that reduce abrupt stalling.  The inability to predict stall restricts the development of aggressive aerodynamic concepts.[4] Some blades (mostly on Enercon) have a winglet to increase performance and/or reduce noise.[21][22]

text: A blade can have a lift-to-drag ratio of 120,[23] compared to 70 for a sailplane and 15 for an airliner.[24]

text: The hub[edit]

text: In simple designs, the blades are directly bolted to the hub and are unable to pitch, which leads to aerodynamic stall above certain windspeeds. In other more sophisticated designs, they are bolted to the pitch bearing, which adjusts their angle of attack with the help of a pitch system according to the wind speed to control their rotational speed.[25] The pitch bearing is itself bolted to the hub. The hub is fixed to the rotor shaft which drives the generator directly or through a gearbox.

text: Blade count[edit]

text: This section includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please help to improve this section by introducing more precise citations. (August 2012) (Learn how and when to remove this template message)

tag: table

text: The number of blades is selected for aerodynamic efficiency, component costs, and system reliability. Noise emissions are affected by the location of the blades upwind or downwind of the tower and the speed of the rotor. Given that the noise emissions from the blades' trailing edges and tips vary by the 5th power of blade speed, a small increase in tip speed can make a large difference.

text:
Wind turbines developed over the last 50 years have almost universally used either two or three blades. However, there are patents that present designs with additional blades, such as Chan Shin's Multi-unit rotor blade system integrated wind turbine.[26]
Aerodynamic efficiency increases with number of blades but with diminishing return. Increasing the number of blades from one to two yields a six percent increase in aerodynamic efficiency, whereas increasing the blade count from two to three yields only an additional three percent in efficiency.[27] Further increasing the blade count yields minimal improvements in aerodynamic efficiency and sacrifices too much in blade stiffness as the blades become thinner.[citation needed]

text: Theoretically, an infinite number of blades of zero width is the most efficient, operating at a high value of the tip speed ratio. But other considerations lead to a compromise of only a few blades.[28]

text: Component costs that are affected by blade count are primarily for materials and manufacturing of the turbine rotor and drive train. Generally, the lower the number of blades, the lower the material and manufacturing costs will be. In addition, the lower the number of blades, the higher the rotational speed can be. This is because blade stiffness requirements to avoid interference with the tower limit how thin the blades can be manufactured, but only for upwind machines; deflection of blades in a downwind machine results in increased tower clearance. Fewer blades with higher rotational speeds reduce peak torques in the drive train, resulting in lower gearbox and generator costs.

text: System reliability is affected by blade count primarily through the dynamic loading of the rotor into the drive train and tower systems. While aligning the wind turbine to changes in wind direction (yawing), each blade experiences a cyclic load at its root end depending on blade position. This is true of one, two, three blades or more. However, these cyclic loads when combined together at the drive train shaft are symmetrically balanced for three blades, yielding smoother operation during turbine yaw. Turbines with one or two blades can use a pivoting teetered hub to also nearly eliminate the cyclic loads into the drive shaft and system during yawing. A Chinese 3.6 MW two-blade is being tested in Denmark.[29] Mingyang won a bid for 87 MW (29 * 3 MW) two-bladed offshore wind turbines near Zhuhai in 2013.[30][31][32]

text: Finally, aesthetics can be considered a factor in that some people find that the three-bladed rotor is more pleasing to look at than a one- or two-bladed rotor.

text: Blade materials[edit]

text: In general, ideal materials should meet the following criteria:

text:
wide availability and easy processing to reduce cost and maintenance
low weight or density to reduce gravitational forces
high strength to withstand strong loading of wind and gravitational force of the blade itself
high fatigue resistance to withstand cyclic loading
high stiffness to ensure stability of the optimal shape and orientation of the blade and clearance with the tower
high fracture toughness
the ability to withstand environmental impacts such as lightning strikes, humidity, and temperature[33]

tag: ul

text: This narrows down the list of acceptable materials. Metals would be undesirable because of their vulnerability to fatigue. Ceramics have low fracture toughness, which could result in early blade failure. Traditional polymers are not stiff enough to be useful, and wood has problems with repeatability, especially considering the length of the blade. That leaves fiber-reinforced composites, which have high strength and stiffness and low density, as a very attractive class of materials for the design of wind turbines.[34]

text: Wood and canvas sails were used on early windmills due to their low price, availability, and ease of manufacture. Smaller blades can be made from light metals such as aluminium. These materials, however, require frequent maintenance. Wood and canvas construction limits the airfoil shape to a flat plate, which has a relatively high ratio of drag to force captured  (low aerodynamic efficiency) compared to solid airfoils. Construction of solid airfoil designs requires inflexible materials such as metals or composites. Some blades also have incorporated lightning conductors.

text:
New wind turbine designs push power generation from the single megawatt range to upwards of 10 megawatts using larger and larger blades. A larger area effectively increases the tip-speed ratio of a turbine at a given wind speed, thus increasing its energy extraction.[35]
Computer-aided engineering software such as HyperSizer (originally developed for spacecraft design) can be used to improve blade design.[36][37]

text: As of 2015 the rotor diameters of onshore wind turbine blades are as large as 130 meters,[38] while the diameter of offshore turbines reach 170 meters.[39] In 2001, an estimated 50 million kilograms of fibreglass laminate were used in wind turbine blades.[40]

text:
An important goal of larger blade systems is to control blade weight. Since blade mass scales as the cube of the turbine radius, loading due to gravity constrains systems with larger blades.[41] Gravitational loads include axial and tensile/ compressive loads (top/bottom of rotation) as well as bending (lateral positions).  The magnitude of these loads fluctuates cyclically and the edgewise moments (see below) are reversed every 180° of rotation.
Typical rotor speeds and design life are ~10 and 20 years, respectively, with the number of lifetime revolutions on the order of 10^8.   Considering wind, it is expected that turbine blades go through ~10^9 loading cycles.
Wind is another source of rotor blade loading.  Lift causes bending in the flapwise direction (out of rotor plane) while air flow around the blade cause edgewise bending (in the rotor plane).
Flapwise bending involves tension on the pressure (upwind) side and compression on the suction (downwind) side.
Edgewise bending involves tension on the leading edge and compression on the trailing edge.

text: Wind loads are cyclical because of natural variability in wind speed and wind shear (higher speeds at top of rotation).

text: Failure in ultimate loading of wind-turbine rotor blades exposed to wind and gravity loading is a failure mode that needs to be considered when the rotor blades are designed. The wind speed that causes bending of the rotor blades exhibits a natural variability, and so does the stress response in the rotor blades. Also, the resistance of the rotor blades, in terms of their tensile strengths, exhibits a natural variability.[42]

text: In light of these failure modes and increasingly larger blade systems, there has been continuous effort toward developing cost-effective materials with higher strength-to-mass ratios. In order to extend the current 20 year lifetime of blades and enable larger area blades to be cost-effective, the design and materials need to be optimized for stiffness, strength, and fatigue resistance.[33]

text: The majority of current commercialized wind turbine blades are made from fiber-reinforced polymers (FRPs), which are composites consisting of a polymer matrix and fibers. The long fibers provide longitudinal stiffness and strength, and the matrix provides fracture toughness, delamination strength, out-of-plane strength, and stiffness.[33] Material indices based on maximizing power efficiency, and having high fracture toughness, fatigue resistance, and thermal stability, have been shown to be highest for glass and carbon fiber reinforced plastics (GFRPs and CFRPs).[43]

text:
Manufacturing blades in the 40 to 50 metre range involves proven fibreglass composite fabrication techniques. Manufactures such as Nordex SE and GE Wind use an infusion process. Other manufacturers use variations on this technique, some including carbon and wood with fibreglass in an epoxy matrix. Other options include preimpregnated ("prepreg") fibreglass and vacuum-assisted resin transfer molding. Each of these options use a glass-fibre reinforced polymer composite constructed with differing complexity. Perhaps the largest issue with more simplistic, open-mould, wet systems are the emissions associated with the volatile organics released. Preimpregnated materials and resin infusion techniques avoid the release of volatiles by containing all VOCs. However, these contained processes have their own challenges, namely the production of thick laminates necessary for structural components becomes more difficult. As the preform resin permeability dictates the maximum laminate thickness, bleeding is required to eliminate voids and ensure proper resin distribution.[40]
One solution to resin distribution a partially preimpregnated fibreglass. During evacuation, the dry fabric provides a path for airflow and, once heat and pressure are applied, resin may flow into the dry region resulting in a thoroughly impregnated laminate structure.[40]

text: Epoxy-based composites have environmental, production, and cost advantages over other resin systems. Epoxies also allow shorter cure cycles, increased durability, and improved surface finish. Prepreg operations further reduce processing time over wet lay-up systems. As turbine blades pass 60 metres, infusion techniques become more prevalent; the traditional resin transfer moulding injection time is too long as compared to the resin set-up time, limiting laminate thickness. Injection forces resin through a thicker ply stack, thus depositing the resin where in the laminate structure before gelation occurs. Specialized epoxy resins have been developed to customize lifetimes and viscosity.[45]

text: Carbon fibre-reinforced load-bearing spars can reduce weight and increase stiffness. Using carbon fibres in 60 metre turbine blades is estimated to reduce total blade mass by 38% and decrease cost by 14% compared to 100% fibreglass. Carbon fibres have the added benefit of reducing the thickness of fiberglass laminate sections, further addressing the problems associated with resin wetting of thick lay-up sections. Wind turbines may also benefit from the general trend of increasing use and decreasing cost of carbon fibre materials.[40]

text: Although glass and carbon fibers have many optimal qualities for turbine blade performance, there are several downsides to these current fillers, including the fact that high filler fraction (10-70 wt%) causes increased density as well as microscopic defects and voids that often lead to premature failure.[33]

text: Recent developments include interest in using carbon nanotubes (CNTs) to reinforce polymer-based nanocomposites. CNTs can be grown or deposited on the fibers, or added into polymer resins as a matrix for FRP structures. Using nanoscale CNTs as filler instead of traditional microscale filler (such as glass or carbon fibers) results in CNT/polymer nanocomposites, for which the properties can be changed significantly at very low filler contents (typically < 5 wt%). They have very low density, and improve the elastic modulus, strength, and fracture toughness of the polymer matrix. The addition of CNTs to the matrix also reduces the propagation of interlaminar cracks which can be a problem in traditional FRPs.[33]

text: Further improvement is possible through the use of carbon nanofibers (CNFs) in the blade coatings. A major problem in desert environments is erosion of the leading edges of blades by wind carrying sand, which increases roughness and decreases aerodynamic performance. The particle erosion resistance of fiber-reinforced polymers is poor when compared to metallic materials and elastomers, and needs to be improved. It has been shown that the replacement of glass fiber with CNF on the composite surface greatly improves erosion resistance. CNFs have also been shown to provide good electrical conductivity (important for lightning strikes), high damping ratio, and good impact-friction resistance. These properties make CNF-based nanopaper a prospective coating for wind turbine blades.[46][47]

text: Another important source of degradation for turbine blades is lightning damage, which over the course of a normal 25-year lifetime is expected to experience a number of lightning strikes throughout its service.[48] The range of damage caused from lightning strikes goes from merely surface level scorching and cracking of the laminate material, to ruptures in the blade or full separation in the adhesives that hold the blade together.[48]It is most common to observe lightning strikes on the tips of the blades, especially in rainy weather due to the copper wiring within attracting lightning.[49] The most common method to combat this, especially in non-conducting blade materials like GFRPs and CFRPs, is to add lightning "arresters", which are merely metallic wiring that provides an uninterrupted path to the ground, skipping the blades and gearbox entirely to eliminate the risk of damage in those components.[49]

text: Blade recycling[edit]

text: The Global Wind Energy Council (GWEC) predicts that wind energy will supply 15.7% of the world’s total energy needs by the year 2020, and 28.5% by the year 2030.[50] This dramatic increase in global wind energy generation will require installation of a newer and larger fleet of more efficient wind turbines and the consequent decommissioning of aging ones. Based on a study carried out by the European Wind Energy Association, in the year 2010 alone, between 110 and 140 kilotons of composites were consumed by the wind turbine industry for manufacturing blades.[51] The majority of the blade material will eventually end up as waste, and in order to accommodate this level of composite waste, the only option is recycling. Typically, glass-fibre-reinforced-polymers (GFRPs) compose of around 70% of the laminate material in the blade. GFRPs hinder incineration and are not combustible.[52] Therefore, conventional recycling methods need to be modified. Currently, depending on whether individual fibres can be recovered, there exists a few general methods for recycling GFRPs in wind turbine blades:

text:
Mechanical Recycling: This method doesn't recover individual fibres. Initial processes involve shredding, crushing, and/or milling. The crushed pieces are then separated into fibre-rich and resin-rich fractions. These fractions are ultimately incorporated into new composites either as fillers or reinforcements.[53]
Chemical Processing/Pyrolysis: Thermal decomposition of the composites is used to recover the individual fibres. For pyrolysis, the material is heated up to 500 °C in an environment without oxygen, thus causing it to break down into lower weight organic substances and/or gaseous products. The glass fibres will generally lose 50% of their initial strength and can now be downcycled for fibre reinforcement applications in paints or concrete.[54] Research has shown that this end of life option is able to recover up to approximately 19 MJ/kg.[55] However, this method has a relatively high cost and requires similar mechanical pre-processing. In addition, it has not yet been modified to satisfy the future need of large scale wind turbine blade recycling.[56]
Direct Structural recycling of composites: Developed to combat the inefficiencies and costs associated with chemical, thermal and mechanical recycling processes, which either reduce the performance properties or only act as filler for other composites. The general idea to this method is to reuse the composite as is, which can be achieved especially in larger composite materials as it can be partitioned in several pieces which can be used in other applications as is, without altering the chemical properties of the composite component. [57]

text: Tower[edit]

text: Tower height[edit]

text:
Wind velocities increase at higher altitudes due to surface aerodynamic drag (by land or water surfaces) and the viscosity of the air. The variation in velocity with altitude, called wind shear, is most dramatic near the surface.
Typically, the variation follows the wind profile power law, which predicts that wind speed rises proportionally to the seventh root of altitude. Doubling the altitude of a turbine, then, increases the expected wind speeds by 10% and the expected power by 34%. To avoid buckling, doubling the tower height generally requires doubling the diameter of the tower as well, increasing the amount of material by a factor of at least four.

text: At night time, or when the atmosphere becomes stable, wind speed close to the ground usually subsides whereas at turbine hub altitude it does not decrease that much or may even increase. As a result, the wind speed is higher and a turbine will produce more power than expected from the 1/7 power law: doubling the altitude may increase wind speed by 20% to 60%. A stable atmosphere is caused by radiative cooling of the surface and is common in a temperate climate: it usually occurs when there is a (partly) clear sky at night. When the (high altitude) wind is strong (a 10-meter wind speed higher than approximately 6 to 7 m/s) the stable atmosphere is disrupted because of friction turbulence and the atmosphere will turn neutral. A daytime atmosphere is either neutral (no net radiation; usually with strong winds and heavy clouding) or unstable (rising air because of ground heating—by the sun). Here again the 1/7 power law applies or is at least a good approximation of the wind profile. Indiana had been rated as having a wind capacity of 30,000 MW, but by raising the expected turbine height from 50 m to 70 m, the wind capacity estimate was raised to 40,000 MW, and could be double that at 100 m.[58]

text: For HAWTs, tower heights approximately two to three times the blade length have been found to balance material costs of the tower against better utilisation of the more expensive active components.

text: Road size restrictions makes transportation of towers with a diameter of more than 4.3 m difficult. Swedish analyses show that it is important to have the bottom wing tip at least 30 m above the tree tops, but a taller tower requires a larger tower diameter.[59] A 3 MW turbine may increase output from 5,000 MWh to 7,700 MWh per year by going from 80 to 125 meter tower height.[60] A tower profile made of connected shells rather than cylinders can have a larger diameter and still be transportable. A 100 m prototype tower with TC bolted 18 mm 'plank' shells has been erected at the wind turbine test center Høvsøre in Denmark and certified by Det Norske Veritas, with a Siemens nacelle. Shell elements can be shipped in standard 12 m shipping containers,[59][61] and 2½ towers per week are produced this way.[62]

text:
As of 2003, typical modern wind turbine installations use towers about 210 ft (65 m) high.
Height is typically limited by the availability of cranes.
This has led to a variety of proposals for "partially self-erecting wind turbines" that, for a given available crane, allow taller towers that put a turbine in stronger and steadier winds, and "self-erecting wind turbines" that can be installed without cranes.[63][64][65][66]

text: Tower materials[edit]

text:
Currently, the majority of wind turbines are supported by conical tubular steel towers. These towers represent 30% – 65% of the turbine weight and therefore account for a large percentage of the turbine transportation costs. The use of lighter materials in the tower could greatly reduce the overall transport and construction cost of wind turbines, however the stability must be maintained.[67]
Higher grade S500 steel costs 20%-25% more than S335 steel (standard structural steel), but it requires 30% less material because of its improved strength. Therefore, replacing wind turbine towers with S500 steel would result in net savings both in weight and cost.[68]

text: Another disadvantage of conical steel towers is that constructing towers that meet the requirements of wind turbines taller than 90 meters proves challenging. High performance concrete shows potential to increase tower height and increase the lifetime of the towers. A hybrid of prestressed concrete and steel has shown improved performance over standard tubular steel at tower heights of 120 meters.[69] Concrete also gives the benefit of allowing for small precast sections to be assembled on site, avoiding the challenges steel faces during transportation.[70] One downside of concrete towers is the higher CO2 emissions during concrete production as compared to steel. However, the overall environmental benefit should be higher if concrete towers can double the wind turbine lifetime.[71]

text: Wood is being investigated as a material for wind turbine towers, and a 100 metre tall tower supporting a 1.5 MW turbine has been erected in Germany. The wood tower shares the same transportation benefits of the segmented steel shell tower, but without the steel resource consumption.[72][73]

text: Connection to the electric grid[edit]

text:
All grid-connected wind turbines, from the first one in 1939 until the development of variable-speed grid-connected wind turbines in the 1970s, were fixed-speed wind turbines.
As recently as 2003, nearly all grid-connected wind turbines operated at exactly constant speed (synchronous generators) or within a few percent of constant speed (induction generators).[74][75]
As of 2011, many operational wind turbines used fixed speed induction generators (FSIG).[76]
As of 2011, most new grid-connected wind turbines are variable speed wind turbines—they are in some variable speed configuration.[76]

text:
Early wind turbine control systems were designed for peak power extraction, also called maximum power point tracking—they attempt to pull the maximum possible electrical power from a given wind turbine under the current wind conditions.[77]
More recent wind turbine control systems deliberately pull less electrical power than they possibly could in most circumstances, in order to provide other benefits, which include:

text:
spinning reserves to quickly produce more power when needed—such as when some other generator suddenly drops from the grid—up to the max power supported by the current wind conditions.[78]
Variable-speed wind turbines can (very briefly) produce more power than the current wind conditions can support, by storing some wind energy as kinetic energy (accelerating during brief gusts of faster wind) and later converting that kinetic energy to electric energy (decelerating, either when more power is needed elsewhere, or during short lulls in the wind, or both).[79][80]
damping (electrical) subsynchronous resonances in the grid[81]
damping (mechanical) resonances in the tower[82][83]

text: The generator in a wind turbine produces alternating current (AC) electricity. Some turbines drive an AC/AC converter—which converts the AC to direct current (DC) with a rectifier and then back to AC with an inverter—in order to match the frequency and phase of the grid. However, the most common method in large modern turbines is to instead use a doubly fed induction generator directly connected to the electricity grid.

text: A useful technique to connect a permanent magnet synchronous generator to the grid is by using a back-to-back converter. Also, we can have control schemes so as to achieve unity power factor in the connection to the grid. In that way the wind turbine will not consume reactive power, which is the most common problem with wind turbines that use induction machines. This leads to a more stable power system. Moreover, with different control schemes a wind turbine with a permanent magnet synchronous generator can provide or consume reactive power. So, it can work as a dynamic capacitor/inductor bank so as to help with the power systems' stability.

text: Below we show the control scheme so as to achieve unity power factor :

text: Reactive power regulation consists of one PI controller in order to achieve operation with unity power factor (i.e. Qgrid = 0 ). It is obvious that IdN has to be regulated to reach zero at steady-state (IdNref = 0).

text: We can see the complete system of the grid side converter and the cascaded PI controller loops in the figure in the right.

text: Foundations[edit]

text: Wind turbines, by their nature, are very tall slender structures,[84] this can cause a number of issues when the structural design of the foundations are considered. The foundations for a conventional engineering structure are designed mainly to transfer the vertical load (dead weight) to the ground, this generally allows for a comparatively unsophisticated arrangement to be used. However, in the case of wind turbines, the force of the wind's interaction with the rotor at the top of the tower creates a strong tendency to tip the wind turbine over. This loading regime causes large moment loads to be applied to the foundations of a wind turbine. As a result, considerable attention needs to be given when designing the footings to ensure that the foundation will resist this tipping tendency.[85]

text: One of the most common foundations for offshore wind turbines is the monopile, a single large-diameter (4 to 6 metres) tubular steel pile driven to a depth of 5-6 times the diameter of the pile into the seabed. The cohesion of the soil, and friction between the pile and the soil provide the necessary structural support for the wind turbine.[86]

text: In onshore turbines the most common type of foundation is a gravity foundation, where a large mass of concrete spread out over a large area is used to resist the turbine loads. Wind turbine size & type, wind conditions and soil conditions at the site are all determining factors in the design of the foundation. [87]

text: Costs[edit]

text: The modern wind turbine is a complex and integrated system. Structural elements comprise the majority of the weight and cost.  All parts of the structure must be inexpensive, lightweight, durable, and manufacturable, under variable loading and environmental conditions. Turbine systems that have fewer failures,[90] require less maintenance, are lighter and last longer will lead to reducing the cost of wind energy.

text: One way to achieve this is to implement well-documented, validated analysis codes, according to a 2011 report from a coalition of researchers from universities, industry, and government, supported by the Atkinson Center for a Sustainable Future.[4]

text: The major parts of a modern turbine may cost (percentage of total): tower 22%, blades 18%, gearbox 14%, generator 8%.[91][92]

text: Design specification[edit]

text:
The design specification for a wind-turbine will contain a power curve and guaranteed availability. With the data from the wind resource assessment it is possible to calculate commercial viability.[1]
The typical operating temperature range is −20 to 40 °C (−4 to 104 °F). In areas with extreme climate (like Inner Mongolia or Rajasthan) specific cold and hot weather versions are required.

text: Wind turbines can be designed and validated according to IEC 61400 standards.[93]

text: Low temperature[edit]

text: Utility-scale wind turbine generators have minimum temperature operating limits which apply in areas that experience temperatures below −20 °C (−4 °F). Wind turbines must be protected from ice accumulation. It can make anemometer readings inaccurate and which, in certain turbine control designs, can cause high structure loads and damage. Some turbine manufacturers offer low-temperature packages at a few percent extra cost, which include internal heaters, different lubricants, and different alloys for structural elements. If the low-temperature interval is combined with a low-wind condition, the wind turbine will require an external supply of power, equivalent to a few percent of its rated power, for internal heating. For example, the St. Leon Wind Farm in Manitoba, Canada, has a total rating of 99 MW and is estimated to need up to 3 MW (around 3% of capacity) of station service power a few days a year for temperatures down to −30 °C (−22 °F). This factor affects the economics of wind turbine operation in cold climates.


document_title: Jennifer Worth

question_text: who did jenny from call the midwife marry

text: Jennifer Worth

text: Biography[edit]

text: Worth, born Jennifer Lee in Clacton-on-Sea, Essex, was raised in Amersham, Buckinghamshire. After leaving school at the age of 15[2] she learned shorthand and typing[3] and became the secretary to the head of Dr Challoner's Grammar School. She then trained as a nurse at the Royal Berkshire Hospital, Reading, and moved to London to receive training to become a midwife.[2]

text: Lee was hired as a staff nurse at the London Hospital in Whitechapel in the early 1950s. With the Sisters of St John the Divine, an Anglican community of nuns, she worked to aid the poor.[2] She was then a ward sister at the Elizabeth Garrett Anderson Hospital in Bloomsbury, and later at the Marie Curie Hospital in Hampstead.[4]

text: She married the artist Philip Worth in 1963, and they had two daughters.[3] (Philip Worth appears as a character in the 2014 Christmas Special portrayed by Ronald Pickup; at the end of the third series episode 8 of the TV series Call the Midwife, Phillip Worth was portrayed by Steven Ashfield, according to IMDb "Phillip Worth".[5]) Worth retired from nursing in 1973 to pursue her musical interests.

text: In 1974, she was appointed a licentiate of the London College of Music, where she taught piano and singing. She obtained a fellowship in 1984. She performed as a soloist and with choirs throughout Britain and Europe. She later began writing, and her first volume of memoirs, Call the Midwife, was published in 2002. The book became a best-seller when it was reissued in 2007. Shadows of the Workhouse (2005; reissued 2008) and Farewell to the East End (2009) also became best-sellers.[2] The trilogy sold almost a million copies in the UK alone.[4] In a fourth volume of memoirs In the Midst of Life, published in 2010, Worth reflects on her later experiences caring for the terminally ill.[6]

text: Activism[edit]

text: Worth was highly critical of Mike Leigh's 2004 film Vera Drake, for depicting the consequences of illegal abortions unrealistically. She argued that the method shown in the movie, far from being fairly quick and painless, was in fact almost invariably fatal for the woman.[7]

text: Death[edit]

text: Worth died on 31 May 2011, having been diagnosed with cancer of the oesophagus earlier in the year.[8] The first episode of the television series Call the Midwife was dedicated to her.

text: Publications[edit]

text:
Eczema and Food Allergy: The Hidden Cause? ISBN 978-1872560182 (1997)
Call the Midwife (First book in the Midwife trilogy) ISBN 978-0297868781 (2002)
Shadows of the Workhouse (Second book in the Midwife trilogy) ISBN 978-0297853268 (2005)
Farewell to the East End (Third book in the Midwife trilogy) ISBN 978-0753823064 (2009)
In the Midst of Life ISBN 978-0297859581 (2010)