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Orc (Middle-earth)
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Orcs
Goblins, Yrch, Rakhâs, Gorgûn
Artist's impression of an Orc of Mordor
Attributes
Founder
Morgoth
Leader(s)
The Great Goblin (in The Hobbit)
Capital
Mount Gundabad, Goblin-town, Barad-dûr, Orthanc
Home world
Middle-earth
Base of operations
Misty Mountains, Mordor, Isengard
Language
Orkish, Black Speech
Races of
Middle-earth
Ainur
Valar
Maiar
Other races
Elves
Men
Hobbits
Dwarves
Ents
Eagles
Orcs
Trolls
Dragons
v
t
e
In J. R. R. Tolkien's fantasy writings, Orcs are a race of creatures who are used as soldiers and henchmen by both the greater and lesser villains of The Silmarillion, The Hobbit and The Lord of the Rings—Morgoth, Sauron and Saruman.
Although not entirely dim-witted and occasionally crafty, they are portrayed as miserable beings, hating everyone including themselves and their masters, whom they serve out of fear. They make no beautiful things, but rather design cunning devices made to hurt and destroy.
In some of his unpublished early work, Tolkien appears to distinguish orcs from goblins. By the time of his published work, however, the terms had become synonymous. The Hobbit generally uses the term goblin, while The Lord of the Rings prefers orc. The opponents of the dwarves in "Dwarf and Goblin War" of The Hobbit are described as orcs in Appendix A of The Lord of the Rings. No distinction is made by size; large orcs, including the Uruk-hai, are just as much goblins as are smaller ones.
Tolkien's The Father Christmas Letters also features goblins; they share traits with those in his Middle-earth writings, including being the arch-enemies of elves.
Contents
[hide]
1 Tolkien's influences
2 Middle-earth terms for Orcs
2.1 Orcs, Goblins, and Uruks
3 Physical appearance
4 Types of Orcs
5 Orkish culture
6 Orcish language
7 The origin of Orcs
7.1 A list of origins, proposed by Tolkien
7.1.1 Made from the earth
7.1.2 East Elves (Avari)
7.1.3 Sentient beasts
7.1.4 Fallen Maiar
7.1.5 Corrupted Men
7.1.6 A mix of corrupted Elves and Men
7.1.7 Some cross-bred with Men
8 Individual Orcs
9 Influence on later fantasy
10 Adaptations
11 See also
12 Notes and references
12.1 Works cited
13 External links
Tolkien's influences[edit]
See also: Orc
Orc is from Old English orcneas, which appears in the epic poem Beowulf, and refers to one of the races who are called the offspring of Cain during the initial description of Grendel ("Þanon untydras ealle onwocon,/eotenas ond ylfe, ond orcneas", ll. 111–112). In a letter of 1954 Tolkien gave orc as "demon" and claimed he used the word because of its "phonetic suitability"—its similarity to various equivalent terms in his Middle-earth languages.[1] In an essay on Elven languages, written in 1954, Tolkien gives meaning of 'orc' as "evil spirit or bogey" and goes on to state that the origin of the Old English word is the Latin name Orcus—god of the underworld.[2]
About the goblins of The Hobbit, Tolkien wrote:
They are not based on direct experience of mine; but owe, I suppose, a good deal to the goblin tradition ... especially as it appears in George MacDonald, except for the soft feet which I never believed in.[1]
Middle-earth terms for Orcs[edit]
In the High-elven tongue Quenya, the word for "Orc" was urco, plural urqui, meaning "bogey", or "bogeyman", that is, something that provokes fear. In the Grey-elven tongue Sindarin, it was orch, plural yrch. In the Dwarven tongue Khuzdul, it was rukhs, plural rakhâs. In the language of the Drúedain or Wild Men, it was gorgûn. In the Black Speech of Mordor, the equivalent was Uruk, as can be seen in Uruk-hai, "Orc-folk". Orc itself is from Rohirric[3] and the Hobbit-language,[4] which shared linguistic roots, but the term is clearly related to the older Elvish words.
Uruk and Uruk-hai were reserved for the Uruks themselves, a special breed or breeds of Orc; they called smaller, weaker Orcs snaga, "slave". The Grey Elves also referred to the Orcs as a whole as the Glamhoth, "noisy horde".[5] The word "goblin" is used to represent the original Hobbit Orc. In The History of Middle-earth Tolkien writes about an Orc captain named Boldog[6] but later specifies that Boldog may have been either a term or a title for another special kind of Orc instead of a personal name.[7]
Orcs, Goblins, and Uruks[edit]
The earliest appearance of goblins in Tolkien's writings is the 1915 poem Goblin Feet, also his first published work, which appeared in the annual volume of Oxford Poetry published by Blackwells. It features quaint elvin creatures, and some 45 years later Tolkien dismissed it as juvenile.
In The Book of Lost Tales the names Orcs and goblin are given to creatures who enslave and war with the Elves. Christopher Tolkien notes that while the author clearly differentiates between "goblins and Orcs" in the Tale of Tinúviel, the two terms appear to be synonymous in the Tale of Turambar. The word Gongs is also used on a few occasions; it appears both distinct from Orcs[8] and as a sub-type of Orc.[9] Christopher Tolkien remarks that Gongs are "evil beings obscurely related to Orcs".[10] Both goblins and Orcs are occasionally mentioned as being "of Melkor" and also acting independently. Orcs, goblins, and gongs appear in Tolkien's two lexicons of elvish languages. The Qenya Lexicon from approximately 1915 defines Orc as meaning "monster, demon", and the Gnomish Lexicon dated 1917 defines Orc as "goblin" and Gong as "one of a tribe of the Orcs, a goblin". Christopher Tolkien also notes that in the latter lexicon, the word Gnome (later Noldor) is an emendation from Goblin.
In The Hobbit the inhabitants of the Misty Mountains who capture the Dwarves of Thorin's Company, and who later fight the Men, Elves, and Dwarves at the Battle of the Five Armies, are identified as goblins, which is largely consistent with the usage in The Book of Lost Tales. The term Orc does occur twice; once in an instance where Gandalf is trying to scare Bilbo by mentioning creatures of the wilderness "goblins, hobgoblins, and orcs of the worst description," and again when the narrator mentions the large goblins ("great Orcs of the mountains"), as well as in the Elvish name of Thorin's sword, Orcrist.
In The Lord of the Rings, Orc is used predominantly, and goblin appears mostly in the hobbits' speech. The second volume of the story, The Two Towers, "goblin" is applied to large orcs of the Uruk-hai:
There were four goblin-soldiers of greater stature, swart, slant-eyed, with thick legs and large hands. They were armed with short broad-bladed swords, not with the curved scimitars usual with Orcs: and they had bows of yew, in length and shape like the bows of Men.[11]
And:
Upon a stake in the middle was set a great goblin head; upon its shattered helm the white badge could still be seen.[12]
The "white badge" mentioned in the latter passage makes it clear that the beheaded goblin was one of Saruman's Uruk-hai. Tolkien writes that these bore a white Elf-rune with the value of "S" on their helmets.
Tolkien also wrote the following note, appearing in some editions of The Hobbit:
Orc is not an English word. It occurs in one or two places but is usually translated goblin (or hobgoblin for the larger kinds). Orc is the hobbits' form of the name given at that time to these creatures, and it is not connected at all with orc, ork, applied to sea-animals of dolphin-kind.[4]
The original edition of The Hobbit and early drafts of The Lord of the Rings first used goblin everywhere and used hobgoblin for larger, more evil goblins. While investigating possible sources for the word "Hobbit", Tolkien realised he had made a mistake in using hob-, which is traditionally used to mean a smaller entity, not a larger one.
In later writings, after The Lord of the Rings, (including The Adventures of Tom Bombadil and many essays published in The Peoples of Middle-earth), Tolkien preferred the spelling Ork, evidently mainly to avoid the form Orcish, which would be naturally pronounced with the c as /s/ instead of /k/ in English. Tolkien indeed used the adjective Orkish.[13]
According to George MacDonald Fraser in The Light's on at Signpost, Tolkien answered a letter on this subject, confirming that Orcs and goblins were indeed identical.
Physical appearance[edit]
Orcs are described as ugly and filthy fanged humanoids. The largest can reach near-human height, but they are almost always shorter, and some are as small as Hobbits (since Frodo and Sam disguise themselves as such when they enter Mordor). In contrast, crossbreeds between Men and Orcs are called "man-high, but with goblin-faces."[14] However, some Orcs are very broad, if not tall. Many Orcs have long arms, like monkeys or apes. Many of them also have crooked backs and legs.
Tolkien describes Orcs explicitly in one of his Letters:
...they are (or were) squat, broad, flat-nosed, sallow-skinned, with wide mouths and slant eyes; in fact degraded and repulsive versions of the (to Europeans) least lovely Mongol-types.[15]
Readers have debated at length the extent and meaning of the racial imagery in Tolkien's writings, including Michael D. C. Drout,[16] Tom Shippey,[17] Stephen Shapiro[18] and Mount Vernon Nazarene University professor Anderson Rearick III.[19]
Types of Orcs[edit]
There is much variation among Orcs. The Uruks (who called themselves Uruk-hai) are larger, more powerful and cruel and "black"; they call smaller and weaker Orcs snaga ("slave"). Sauron apparently bred specialized types, such as the "super-soldier" Uruk-hai, and smaller tracker Orcs or "Snufflers" (described as "of a small breed, black-skinned").[20] Early texts in The History of Middle-earth mention Maiar incarnate in Orc-bodies called Boldogs (see below).
Tolkien wrote of Saruman crossbreeding Orcs and Men, producing Men-orcs and Orc-men in "Myths Revisited" in Morgoth's Ring.[citation needed] The half-orcs and goblin-men, mentioned by Gamling at Helm's Deep, seem likely to have been crossbreeds, and they are not described much beyond being "creatures of Isengard", "that the foul craft of Saruman has bred", and that "they will not quail at the sun". The first encounter with one of these half-goblins occurs in The Fellowship of the Ring when the Hobbits encounter a suspicious character they refer to as the Southerner who is in cahoots with Bill Ferny (the Southerner turns out to be a spy of Saruman and possibly Sauron, and possibly a double spy for both as Aragorn suggests). Half-orcs are described later on by Meriadoc Brandybuck, who saw them marching out of Isengard, as "horrible: man-high, but with goblin-faces, sallow, leering, squint-eyed." The hobbits occasionally encounter unusual-looking Men such as the "ruffians" in the Shire, implying some of these might be half-orcs. During the scouring of the Shire it is stated that the ruffians that have invaded include half-orcs and more of the sallow-skinned, slant/squinty eyed folks like the Southerner spy.
The Uruk-hai of Saruman, exemplified by Uglúk, are shown to be physically different from the regular Orcs of Sauron. They are taller and have more human-like proportions while the latter are shorter and have longer arms (according to the description of Grishnákh). They also grudgingly tolerate the sunlight better. The Uruk-hai are different from most of the "Northerners", who came down from the Misty Mountains. These are said to be smaller than Grishnákh, who is "a short crook-legged creature".[21]
Some of the Northerners, called "larger and bolder Northerners", stayed with Saruman's Uruk-hai when most of the Northern Orcs deserted. The deserters, "flagging in the rays of the bright sun", were later overtaken by the party of the Uruk-hai, showing differing tolerance to the sunlight.
Orcs served Morgoth in Angband and Sauron in Mordor. By the time of the War of the Ring, some served Saruman in Isengard. However, some Orcs seem to have worked independently. Before and during the time of The Hobbit, some Orcs had Mount Gundabad as their capital, the Orcs of the Misty Mountains were apparently ruled by one "Great Goblin", the former Dwarf-realm of Moria was held by orcs under one Azog and then his son Bolg, and one Golfimbul had led the orcs of Mount Gram in a foray into the Shire.
Orkish culture[edit]
Tolkien does not elaborate on Orc culture and customs. Orcs know some form of healing arts (as the Orc-band apply harsh but effective Orkish medicine to Pippin's and Merry's injuries while they are in their captivity). Also their armour, though inferior to that of Elves and Dwarves, is serviceable. Orcs often use poisoned blades (as Aragorn observes while inspecting a wound received by Sam)[22] and arrows (as they use on Isildur). They like to sing horrible songs (as in The Hobbit). The Goblins of the Misty Mountains were a smaller breed of Orc, and invented horrid machines used to torture and kill things. In some texts,[citation needed] Tolkien suggests that after the fall of Morgoth, some of his Orcs set up petty kingdoms of their own.
Tolkien indicates that Orcs are "always hungry".[23] Orcs eat all manner of flesh, including men and horses, and there are frequent hints of cannibalism among Orcs. Grishnákh, leader of the Mordor Orcs, accuses Saruman's Uruks of eating Orc-flesh, which they angrily deny.[21] In Cirith Ungol, Gorbag suggests that Frodo (recently poisoned by Shelob) should "go in the pot"; Shagrat indicates that Gorbag could be "for the pot" for making such a suggestion.[24] Shagrat threatens to eat a disobedient orc, and after killing Gorbag he licks his blood from the blade.[25]
Orcish language[edit]
The Orcs had no language of their own, merely a pidgin of many various languages. However, individual tribes developed dialects that differed so widely that Westron, often with a crude accent, was used as a common language. A few words of the Black Speech are common among Orcs: ghâsh ("fire"), sharkû ("old man", leading to Saruman's nickname "Sharkey"), snaga ("slave"), and Uruk ("orc"). Another Orkish word is tark ("Man of Gondor") from Westron and ultimately Quenya tarkil.
When Sauron returned to power in Mordor in the Third Age, Black Speech was used by the captains of his armies and by his servants in Barad-dûr. A substantial sample of debased Black Speech/Orkish can be found in The Two Towers, where a "yellow-fanged" guard Orc of Mordor curses Uglúk of Isengard:
Uglúk u bagronk sha pushdug Saruman-glob búbhosh skai!
In The Peoples of Middle-earth,[26] Tolkien gives the translation: "Uglúk to the cesspool, sha! the dungfilth; the great Saruman-fool, skai!". However, in a note published in Vinyar Tengwar he gives an alternative translation: "Uglúk to the dung-pit with stinking Saruman-filth, pig-guts, gah!"[27]
Alexandre Nemirovsky speculates that Tolkien may have drawn upon the language of the ancient Hittites and Hurrians for Black Speech and Orkish.[28]
The origin of Orcs[edit]
The origin of Orcs is an open question. Tolkien developed various origins for his Orcs throughout his life but died before he could fully revise The Silmarillion with his final view on their origins and nature. Tolkien's Orc origin ideas were published posthumously in The Silmarillion, with other versions of events appearing later in The History of Middle-earth.
In Tolkien's writings, evil is not capable of independent creation, making it unlikely that the Vala Morgoth, who was the first to produce them, could create them from nothing.
No female Orcs are ever mentioned by Tolkien in any publication. However, in the published Silmarillion it is stated that Orcs "had life and multiplied after the manner of the Children of Ilúvatar", implying that they exist; in The Hobbit the Orc Bolg is the son of one Azog, while Gollum is described as having eaten a young Goblin-imp (Goblins often being synonymous with orcs) shortly before he first met Bilbo (which seems to be alluded to in The Lord of the Rings films when Gollum goes on (with himself) about how unpleasant-tasting orcs are and that sweet Hobbit meat would suit Shelob better).
In an unpublished letter, written in 1963 to a Mrs. Munsby (and auctioned in 2002 at Sotheby's), Tolkien confirmed that female Orcs did exist. He wrote:
"There must have been orc-women. But in stories that seldom if ever see the Orcs except as soldiers of armies in the service of the evil lords we naturally would not learn much about their lives. Not much was known."[29]
Compare this with Tolkien's more thorough explanation of the existence of Dwarf-women, given in the Appendix. Dwarf-women seldom leave their underground cities, and are not encountered as frontline soldiers in war, but that does not mean they do not exist.
It is said in The Silmarillion:[30]
"But of those unhappy ones who were ensnared by Melkor little is known of a certainty. For who of the living has descended into the pits of Utumno, or has explored the darkness of the counsels of Melkor? Yet this is held true by the wise of Eressëa, that all those of the Quendi who came into the hands of Melkor, ere Utumno was broken, were put there in prison, and by slow arts of cruelty were corrupted and enslaved; and thus did Melkor breed the hideous race of the Orcs in envy and mockery of the Elves, of whom they were afterwards the bitterest foes."
This text refers to the Quendi who ran and hid at the sight of Oromë when he came to lead them from Cuiviénen westward. These "corrupted elves" were the first orcs. There are various races of orcs (though with later races of orcs came different physical and non-physical characteristics like increasing tolerance to sunlight) all identical in their hate for everything that Ilúvatar and the Valar had constructed (including themselves) to resemble the hate that lay within Melkor.
A list of origins, proposed by Tolkien[edit]
Made from the earth[edit]
According to the oldest "theory" proposed by J.R.R. Tolkien (found in The Fall of Gondolin, from The Book of Lost Tales, circa 1917—the first tale of Middle-earth to be written in full), Orcs were made of slime through the sorcery of Morgoth: "bred from the heats and slimes of the earth".[31]
However, it is consistently stated in Tolkien's other writings, with regard to his creation myth, that only Eru Ilúvatar (God) can create new life from nothing. Therefore, by whatever means the orcs came into being, it is certain that either they were "descended" from other beings or a deliberate manifestation of Ilúvatar's thought.
East Elves (Avari)[edit]
The Silmarillion contains a suggestion that Orcs are descended from East Elves (Avari) captured by Melkor, their minds and bodies distorted and corrupted.[30]
There is evidence of the immortality, or otherwise long life of Orcs. They certainly did live for at the very least hundreds of years, since Bolg was the son of Azog and his death occurred over 140 years after the death of his father. This theory is consistent with a statement made in the "Myths Transformed" essay of Morgoth's Ring that the Orcs had short lifespans in relation to the Númenóreans.
This corrupted elves origin is probably the one used in Peter Jackson's live action films. In the film of The Lord of the Rings: The Fellowship of the Ring, Saruman says:
"Do you know how the Orcs first came into being? They were elves once, taken by the dark powers, tortured and mutilated. A ruined and terrible form of life..."
Of course this leaves open the possibility of one of the mixed origins (see below) being true in the films, as this was how they "first" appeared, not discounting other corrupted creatures or men being added to the ranks later.
Sentient beasts[edit]
Another of Tolkien's theories proposes that Orcs may have begun as soulless beasts of vaguely humanoid shapes, empowered by the will of the Dark Lord (Morgoth) and learning language only as parrots do:
"The Orcs were beasts of humanized shape (to mock Men and Elves) deliberately perverted / converted into a more close resemblance to Men. Their 'talking' was really reeling off 'records' set in them by Melkor. Even their rebellious critical words – he knew about them. Melkor taught them speech and as they bred they inherited this; and they had just as much independence as have, say, dogs or horses of their human masters. This talking was largely echoic (cf. parrots)."[32]
Later in the same text he theorizes that some Orcs may have been Elves, who then mated with these beasts and with Men.
"It remains therefore terribly possible there was an Elvish strain in the Orcs. These may then even have been mated with beasts (sterile!) – and later Men. Their life-span would be diminished. And dying they would go to Mandos and be held in prison till the End."[32]
It is certain all Orcs were dependent on the Dark Lord in various ways: after their leader was defeated, the Orcs were confused and dismayed, and easily scattered by their enemies. In the millennia after Morgoth's defeat and banishment from Arda, they were without a leader, and degenerated to small, quarrelsome tribes hiding in the Misty Mountains. Only when Sauron returned to power did they begin to reclaim some of their old standing. The same happened after Sauron's defeat by the Last Alliance of Elves and Men: only when Sauron returned as the Necromancer of Mirkwood did the Orcs become a real danger for Middle-earth again.
Fallen Maiar[edit]
There are hints in the History of Middle-earth series of books, (especially in Morgoth's Ring in the section "Myths Transformed"), that some Orc leaders, such as the First Age's Boldog, or the Great Goblin encountered by Bilbo and the Dwarves, may in fact have been fallen Maiar which had taken Orc form:
"Some of these things may have been delusions and phantoms; but some were, no doubt, shapes taken by the servants of Melkor, mocking and degrading the very forms of the Children [of Ilúvatar]. For Melkor had in his service great numbers of the Maiar, who had the power, as had their Master, of taking visible and tangible shape in Arda."[33]
"Boldog (…) is a name that occurs many times in the tales of the War. But it is possible that Boldog was not a personal name, and either a title, or else the name of a kind of creature: the Orc-formed Maiar, only less formidable than the Balrogs".[34]
"Melkor had corrupted many spirits—some great, as Sauron, or less so, as Balrogs. The least could have been primitive (and much more powerful and perilous) Orcs; but by practising when embodied procreation they would (cf. Melian) [become] more and more earthbound, unable to return to spirit-state (even demon-form), until released by death (killing), and they would dwindle in force."[32]
Corrupted Men[edit]
While Tolkien at some point saw all Orcs as descended from the original corrupted and tortured Elves, later comments of his indicate, according to Christopher Tolkien in Morgoth's Ring "Myths Transformed" text X, that he began to feel uncomfortable with this theory. At about the same time he removed the references to the Thrall-Ñoldorin, he also began searching for a new origin for the Orcs. It seems Tolkien wanted to change the origin of the Orcs to make them corrupted and twisted Humans. He says of this Human origin view of the Orcs:
"This view of the origin of the Orcs thus meets with difficulties of chronology. But though Men may take comfort in this, the theory remains nonetheless the most probable. It accords with all that is known of Melkor, and of the nature and behaviour of Orcs – and of Men. Melkor was impotent to produce any living thing, but skilled in the corruption of things that did not proceed from himself, if he could dominate them."[33]
Also in Unfinished Tales there is a passage about the Drúedain which says :
"To the unfriendly who, not knowing them well, declared that Morgoth must have bred the Orcs from such a stock the Eldar answered: 'Doubtless Morgoth, since he can make no living thing, bred Orcs from various kinds of Men, but the Drúedain must have escaped his shadow; for their laughter and the laughter of Orcs are as different as the light of Aman from the darkness of Angband.' But some thought, nonetheless, that there had been a remote kinship, which accounted for their special enmity. Orcs and Drûgs each regarded the other as renegades."[35]
Tolkien would have had to change the prehistory of Arda, for the awakening of Men to happen earlier, for there to have been Men for Morgoth or Sauron to corrupt.
A mix of corrupted Elves and Men[edit]
A late idea of Tolkien seems to be that Orcs had a mixed origin of Elves and Men. Text IX of the "Myths Transformed" section of Morgoth's Ring shows this view. The text has no date, but uses the late spelling "Ork" instead of "Orc". This new spelling was adopted in a note of 1969:[33]
"Since Melkor could not 'create' an independent species, but had immense powers of corruption and distortion of those that came into his power, it is probable that these Orks had a mixed origin. Most of them plainly (and biologically) were corruptions of Elves (and probably later also of Men). But always among them (as special servants and spies of Melkor, and as leaders) there must have been numerous corrupted minor spirits who assumed similar bodily shapes. (These would exhibit terrifying and demonic characters.)"[36]
Some cross-bred with Men[edit]
Tolkien also suggested that Men were cross-bred with Orcs under Morgoth's lieutenant, Sauron (and possibly under Morgoth himself). The process was later repeated during the War of the Ring by Saruman. This possibly refers to the way the Uruk-hai and the Half-orcs were created, in The Lord of the Rings.
"There is no doubt that long afterwards, in the Third Age, Saruman rediscovered this, or learned of it in lore, and in his lust for mastery committed this, his wickedest deed: the interbreeding of Orcs and Men, producing both Men-orcs large and cunning, and Orc-men treacherous and vile."[33]
‘But these creatures of Isengard, these half-orcs and goblin-men that the foul craft of Saruman has bred, they will not quail at the sun,’[37]
The first appearance of these half-goblins occurs in The Fellowship of the Ring in describing one known as the Southerner, a spy of Saruman's;
In one of the windows he caught a glimpse of a sallow face with sly, slanting eyes; but it vanished at once. ‘So that’s where that southerner is hiding!’ he thought. ‘He looks more than half like a goblin.’[38]
Further description follows in The Two Towers.
But there were some others that were horrible: man-high, but with goblin-faces, sallow, leering, squint-eyed. Do you know, they reminded me at once of that Southerner at Bree; only he was not so obviously orc-like as most of these were.’[39]
We had many of these half-orcs to deal with at Helm’s Deep. It seems plain now that that Southerner was a spy of Saruman’s; but whether he was working with the Black Riders, or for Saruman alone, I do not know. It is difficult with these evil folk to know when they are in league, and when they are cheating one another.[39]
In the 'Scouring of the Shire', there is further mention of the half-orcs under Sharkey's control, and they are described as men having squinty (or slanty) eyes and sallow complexion (a description used to describe the Southerner, Saruman's spy in The Fellowship of the Ring, as well as some of the orcs in The Two Towers). Which seems to suggest that they look mostly human but share some of the features of the orcs.
they were disturbed to see half a dozen large ill-favoured Men lounging against the inn-wall; they were squint-eyed and sallow-faced. ‘Like that friend of Bill Ferny’s at Bree,’ said Sam. ‘Like many that I saw at Isengard,’ muttered Merry.[40]
‘Of all the ends to our journey that is the very last I should have thought of: to have to fight half-orcs and ruffians in the Shire itself - to rescue Lotho Pimple!’[41]
Individual Orcs[edit]
Main article: List of Middle-earth Orcs
See also: List of original characters in The Lord of the Rings film series
Influence on later fantasy[edit]
Tolkien's Orcs have been a major influence on fantasy fiction and games; they are the literary precursors of the Orcs (and similar races) of many different settings. The Orcs of Warhammer Fantasy, Dungeons & Dragons and other games most often differ from Tolkien's Orcs in that they are taller than Humans and usually have green or greyish-green skin rather than dark or yellowish skin. A notable exception are the Orcs in the most popular German role playing game The Dark Eye, which like Tolkien's orcs are small and dark, but also furry. The world of Hârn has an Orc-inspired race known as Gargun, whose name recalls the term gorgûn ("orcs") from the language of Tolkien's Druedain.
C. S. Lewis may have inserted a nod to his friend's Orcs in The Lion, the Witch and the Wardrobe. When Aslan goes to his death on the Stone Table, the narrator mentions various evil creatures gathered around the White Witch—including "Orknies". (The name is also directly based on the Old English term above).
Adaptations[edit]
Orcs have been featured in many adaptations of Tolkien's Middle-earth writings, from film to stage to video games. The Goblins in the 1977 animated adaptation of The Hobbit were likened to the work of Maurice Sendak.[42] They are portrayed in exactly the same manner as the Orcs in the sequel The Return of the King (1980 film).
Some adaptations have made Goblins distinct from Orcs. This was implied in New Line Cinema's The Lord of the Rings film trilogy directed by Peter Jackson, and made explicit in The Hobbit: An Unexpected Journey, where orcs and goblins are portrayed as distinctly different races. Elven blades are described as turning blue when "orcs or goblins are near", a departure from the source text, and goblins have a notably different appearance in the film from orcs.
This distinction can also be seen in the real-time strategy games The Lord of the Rings: War of the Ring and The Lord of the Rings: The Battle for Middle-earth II. In the former, Goblins can be used alongside common Orcs and Uruk-hai, while in the latter Goblins get their own playable faction. The same is true for the MMORPG The Lord of the Rings Online. Goblins are depicted as a race distinct from Orcs.
In the film The Lord of the Rings: The Fellowship of the Ring some Uruk-hai are seen being birthed full-grown from what appear to be sacs in muddy pits. (This is used as a device to allow Saruman to build his army practically overnight, as opposed to taking the time to breed his "improved" Orcs through more conventional means.)
In The Rise of the Witch-king, an expansion pack for The Battle for Middle-earth II, the Angmar faction uses "Gundabad Orcs" as ordinary foot soldiers, referring to their capital of Mount Gundabad. Like the Goblins of the Misty Mountains, they sometimes ride Wargs into battle.
In the video game Middle-earth: Shadow of Mordor, the Orc hierarchy in Mordor plays a pivotal role in both the story and gameplay.
See also[edit]
Middle-earth portal
Battle of the Hornburg
Boromir
List of Middle-earth Orcs
Túrin Turambar
War of Wrath
Notes and references[edit]
^ Jump up to: a b Carpenter 1981, Letter No. 144
Jump up ^ Tolkien, J. R. R. (1994), Christopher Tolkien, ed., The War of the Jewels, Boston: Houghton Mifflin, ISBN 0-395-71041-3
Jump up ^ Tolkien 1955, "Appendix F: The Languages and Peoples of the Third Age": "Orc is the form of the name that other races had for this foul people as it was in the language of Rohan."
^ Jump up to: a b What was the relationship between Orcs and Goblins? from The Tolkien Meta-FAQ by Steuard Jensen. Brackets by eds.
Jump up ^ Tolkien, J. R. R. (1980), Christopher Tolkien, ed., Unfinished Tales, Boston: Houghton Mifflin, "Of Tuor and his Coming to Gondolin", ISBN 0-395-29917-9
Jump up ^ Tolkien, J. R. R. (1985), Christopher Tolkien, ed., The Lays of Beleriand, Boston: Houghton Mifflin, "The Lay of Leithian", ISBN 0-395-39429-5
Jump up ^ Tolkien 1993, "Myths Transformed"
Jump up ^ Tolkien 1984, "The Nauglafring"
Jump up ^ Tolkien 1984, "Gilfanon's Tale"
Jump up ^ Tolkien 1984, "The History of Eriol or Aelfwine"
Jump up ^ Tolkien 1954, "The Departure of Boromir"
Jump up ^ Tolkien 1954, "The Riders of Rohan"
Jump up ^ Tolkien 1996
Jump up ^ Tolkien 1954, "Flotsam and Jetsam"
Jump up ^ Carpenter 1981, Letter No. 210
Jump up ^ Drout, Michael D. C. (2006). J.R.R. Tolkien Encyclopedia: Scholarship and Critical Assessment. Taylor & Francis, Inc. p. 558. ISBN 978-0-415-96942-0. Retrieved 25 March 2014.
Jump up ^ Young, Helen (2010). "Diversity and Difference: Cosmopolitanism and The Lord of the Rings". Journal of the Fantastic in the Arts. 21 (3).
Jump up ^ Bhatia, Shyam (8 January 2003). "The Lord of the Rings rooted in racism: Academic". Rediff.com.
Jump up ^ Rearick, Anderson (2004). "Why is the only good orc a dead orc? The dark face of racism examined in Tolkien's world" (PDF). Modern Fiction Studies. 50 (4).
Jump up ^ Tolkien 1955, "The Land of Shadow"
^ Jump up to: a b Tolkien 1954, "The Uruk-hai"
Jump up ^ Tolkien, The Fellowship of the Ring, "Lothlórien".
Jump up ^ Tolkien, J. R. R. (2012). The Hobbit. Houghton Mifflin Harcourt. p. 60. ISBN 978-0-54795-197-3.
Jump up ^ Tolkien 1954, "The Choices of Master Samwise"
Jump up ^ Tolkien 1955, "The Tower of Cirith Ungol"
Jump up ^ Tolkien 1996, Part One: the Prologue and Appendices to The Lord of the Rings. Draft of Appendix F.
Jump up ^ Hostetter, Carl F. (November 1992). "Ugluk to the Dung-pit". Vinyar Tengwar. The Elvish Linguistic Fellowship (26).
Jump up ^ Fauskanger, Helge K. "Orkish and the Black Speech – base language for base purposes". Ardalambion. University of Bergen.
Jump up ^ "The Science of Middle-earth: Sex and the Single Orc". TheOneRing.net. Retrieved 29 May 2009.
^ Jump up to: a b Tolkien, J. R. R. (2004). The Silmarillion. HarperCollins. p. 40. ISBN 0-00-717302-4.
Jump up ^ Tolkien 1984, p. 159
^ Jump up to: a b c Tolkien 1993, "Myths transformed", text VIII
^ Jump up to: a b c d Tolkien 1993, "Myths transformed", text X
Jump up ^ Tolkien 1993, "Myths transformed", author's footnote to the text X
Jump up ^ Unfinished Tales, "The Drúedain"
Jump up ^ Tolkien 1993, "Myths transformed", Text IX
Jump up ^ Tolkien 2009, p. 536
Jump up ^ Tolkien 2009, pp. 180–181
^ Jump up to: a b Tolkien 2009, p. 566
Jump up ^ Tolkien 2009, p. 1004
Jump up ^ Tolkien 2009, p. 1006
Jump up ^ O'Connor, John J. (November 25, 1977). "The Hobbit (review)". New York Times.
Works cited[edit]
Carpenter, Humphrey, ed. (1981), The Letters of J. R. R. Tolkien, Boston: Houghton Mifflin, ISBN 0-395-31555-7
Tolkien, J. R. R. (1954), The Two Towers, The Lord of the Rings, Boston: Houghton Mifflin (published 1987), ISBN 0-395-08254-4
Tolkien, J. R. R. (1955), The Return of the King, The Lord of the Rings, Boston: Houghton Mifflin (published 1987), ISBN 0-395-08256-0
Tolkien, J. R. R. (1984), Christopher Tolkien, ed., The Book of Lost Tales, 2, Boston: Houghton Mifflin, ISBN 0-395-36614-3
Tolkien, J. R. R. (1993), Christopher Tolkien, ed., Morgoth's Ring, Boston: Houghton Mifflin, ISBN 0-395-68092-1
Tolkien, J. R. R. (2009). The Lord of the Rings (Kindle ed.). HarperCollins.
External links[edit]
Wikimedia Commons has media related to Middle-earth Orcs.
"Orcs". Tolkien Gateway.
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Transformer types
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Circuit symbols
Transformer with two windings and iron core.
Transformer with three windings. The dots show the relative configuration of the windings.
Transformer with electrostatic screen preventing capacitive coupling between the windings.
An electric arc furnace the transformer has heavy copper bus for the low voltage winding, which can be rated for tens of thousands of amperes. They are immersed in oil for cooling and insulation, and are designed to survive frequent short circuits.
A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional parts.
Contents
[hide]
1 Power transformers
1.1 Laminated core
1.2 Toroidal
1.3 Autotransformer
1.4 Variable autotransformer
1.5 Induction regulator
1.6 Polyphase transformer
1.7 Grounding transformer
1.8 Phase-shifting transformer
1.9 Variable-frequency transformer
1.10 Leakage or stray field transformers
1.10.1 Uses
1.11 Resonant transformer
1.11.1 Constant voltage transformer
1.12 Ferrite core
1.12.1 Planar transformer
1.13 Oil cooled transformer
1.14 Cast resin transformer
1.15 Isolating transformer
2 Instrument transformer
2.1 Current transformer
2.2 Voltage transformer or potential transformer
2.3 Combined instrument transformer
3 Pulse transformer
4 RF transformer
4.1 Air-core transformer
4.2 Ferrite-core transformer
4.3 Transmission-line transformer
4.4 Balun
5 IF transformer
6 Audio transformer
6.1 Loudspeaker transformer
6.2 Output transformer
6.3 Small signal transformer
6.4 Interstage and coupling transformers
7 Other types
7.1 Transactor
7.2 Hedgehog
7.3 Variometer and variocoupler
7.4 Rotary transformer
7.5 Variable differential transformer
7.6 Resolver and synchro
8 See also
9 References
Power transformers[edit]
Laminated core[edit]
Laminated core transformer
This is the most common type of transformer, widely used in electric power transmission and appliances to convert mains voltage to low voltage to power electronic devices. They are available in power ratings ranging from mW to MW. The insulated laminations minimizes eddy current losses in the iron core.
Small appliance and electronic transformers may use a split bobbin, giving a high level of insulation between the windings. The rectangular cores are made up of stampings, often in E-I shape pairs, but other shapes are sometimes used. Shields between primary and secondary may be fitted to reduce EMI (electromagnetic interference), or a screen winding is occasionally used.
Small appliance and electronics transformers may have a thermal cut-out built into the winding, to shut-off power at high temperatures to prevent further overheating.
Toroidal[edit]
Toroidal transformer
Doughnut shaped toroidal transformers save space compared to E-I cores, and may reduce external magnetic field. These use a ring shaped core, copper windings wrapped round this ring (and thus threaded through the ring during winding), and tape for insulation.
Toroidal transformers have a lower external magnetic field compared to rectangular transformers, and can be smaller for a given power rating. However, they cost more to make, as winding requires more complex and slower equipment.
They can be mounted by a bolt through the center, using washers and rubber pads or by potting in resin.
Autotransformer[edit]
Main article: Autotransformer
An autotransformer has one winding that is tapped at some point along the winding. Voltage is applied across a portion of the winding, and a higher (or lower) voltage is produced across another portion of the same winding. The equivalent power rating of the autotransfomer is lower than the actual load power rating. It is calculated by: load VA × (|Vin – Vout|)/Vin.[1] For example, an auto transformer that adapts a 1000 VA load rated at 120 Volts to a 240 Volt supply has an equivalent rating of at least: 1,000VA × (240V – 120V) / 240V = 500VA. However, the actual rating (shown on the tally plate) must be at least 1000 VA.
For voltage ratios that don't exceed about 3:1, an autotransformer is cheaper, lighter, smaller, and more efficient than an isolating (two-winding) transformer of the same rating.[2] Large three-phase autotransformers are used in electric power distribution systems, for example, to interconnect 33 kV and 66 kV sub-transmission networks.[citation needed]
Variable autotransformer[edit]
Variable autotransformer
Main article: Autotransformer § Variable autotransformers
By exposing part of the winding coils of an autotransformer, and making the secondary connection through a sliding carbon brush, an autotransformer with a near-continuously variable turns ratio can be obtained, allowing for wide voltage adjustment in very small increments.
Induction regulator[edit]
Main article: Induction regulator
The induction regulator is similar in design to a wound-rotor induction motor but it is essentially a transformer whose output voltage is varied by rotating its secondary relative to the primary—i.e., rotating the angular position of the rotor. It can be seen as a power transformer exploiting rotating magnetic fields. The major advantage of the induction regulator is that unlike variacs, they are practical for transformers over 5 kVA. Hence, such regulators find widespread use in high-voltage laboratories. [3]
Polyphase transformer[edit]
A high-voltage transformer being dismantled
Cutaway view of a polyphase transformer
For polyphase systems, multiple single-phase transformers can be used, or all phases can be connected to a single polyphase transformer. For a three phase transformer, the three primary windings are connected together and the three secondary windings are connected together.[4] Examples of connections are wye-delta, delta-wye, delta-delta and wye-wye. A vector group indicates the configuration of the windings and the phase angle difference between them. If a winding is connected to earth (grounded), the earth connection point is usually the center point of a wye winding. If the secondary is a delta winding, the ground may be connected to a center tap on one winding (high leg delta) or one phase may be grounded (corner grounded delta). A special purpose polyphase transformer is the zigzag transformer. There are many possible configurations that may involve more or fewer than six windings and various tap connections.
Three-phase transformers 380kV/110kV and 110kV/20kV
Grounding transformer[edit]
Main article: Earthing transformer
Grounding or earthing transformers let three wire (delta) polyphase system supplies accommodate phase to neutral loads by providing a return path for current to a neutral. Grounding transformers most commonly incorporate a single winding transformer with a zigzag winding configuration but may also be created with a wye-delta isolated winding transformer connection.
Phase-shifting transformer[edit]
Main article: Quadrature booster
This is a specialized type of transformer which can be configured to adjust the phase relationship between input and output. This allows power flow in an electric grid to be controlled, e.g. to steer power flows away from a shorter (but overloaded) link to a longer path with excess capacity.
Variable-frequency transformer[edit]
Main article: Variable-frequency transformer
A variable-frequency transformer is a specialized three-phase power transformer which allows the phase relationship between the input and output windings to be continuously adjusted by rotating one half. They are used to interconnect electrical grids with the same nominal frequency but without synchronous phase coordination.
Leakage or stray field transformers[edit]
Leakage transformer
A leakage transformer, also called a stray-field transformer, has a significantly higher leakage inductance than other transformers, sometimes increased by a magnetic bypass or shunt in its core between primary and secondary, which is sometimes adjustable with a set screw. This provides a transformer with an inherent current limitation due to the loose coupling between its primary and the secondary windings. In this case, it is short-circuit inductance which is actually acting as a current limiting parameter. The output and input currents are low enough to prevent thermal overload under all load conditions—even if the secondary is shorted.
Uses[edit]
Leakage transformers are used for arc welding and high voltage discharge lamps (neon lights and cold cathode fluorescent lamps, which are series connected up to 7.5 kV AC). It acts then both as a voltage transformer and as a magnetic ballast.
Other applications are short-circuit-proof extra-low voltage transformers for toys or doorbell installations.
Resonant transformer[edit]
Further information: Resonant inductive coupling
Further information: Tesla coil § Resonant transformer
A resonant transformer is a transformer in which one or both windings has a capacitor across it and functions as a tuned circuit. Used at radio frequencies, resonant transformers can function as high Q factor bandpass filters. The transformer windings have either air or ferrite cores and the bandwidth can be adjusted by varying the coupling (mutual inductance). One common form is the IF (intermediate frequency) transformer, used in superheterodyne radio receivers. They are also used in radio transmitters.
Resonant transformers are also used in electronic ballasts for gas discharge lamps, and high voltage power supplies. They are also used in some types of switching power supplies.[5] Here the short-circuit inductance value is an important parameter that determines the resonance frequency of the resonant transformer. Often only secondary winding has a resonant capacitor (or stray capacitance) and acts as a serial resonant tank circuit. When the short-circuit inductance of the secondary side of the transformer is Lsc and the resonant capacitor (or stray capacitance) of the secondary side is Cr, The resonance frequency ωs of 1' is as follows
ω s = 1 L s c C r = 1 ( 1 − k 2 ) L s C r {\displaystyle \omega _{s}={\frac {1}{\sqrt {L_{sc}C_{r}}}}={\frac {1}{\sqrt {(1-k^{2})L_{s}C_{r}}}}}
The transformer is driven by a pulse or square wave for efficiency, generated by an electronic oscillator circuit. Each pulse serves to drive resonant sinusoidal oscillations in the tuned winding, and due to resonance a high voltage can be developed across the secondary.
Applications:
Intermediate frequency (IF) transformer in superheterodyne radio receiver
Tank transformers in radio transmitters
Tesla coil
CCFL inverter
Oudin coil (or Oudin resonator; named after its inventor Paul Oudin)
D'Arsonval apparatus
Ignition coil or induction coil used in the ignition system of a petrol engine
Electrical breakdown and insulation testing of high voltage equipment and cables. In the latter case, the transformer's secondary is resonated with the cable's capacitance.
Constant voltage transformer[edit]
See also: Voltage regulator § Constant-voltage transformer
By arranging particular magnetic properties of a transformer core, and installing a ferro-resonant tank circuit (a capacitor and an additional winding), a transformer can be arranged to automatically keep the secondary winding voltage relatively constant for varying primary supply without additional circuitry or manual adjustment. Ferro-resonant transformers run hotter than standard power transformers, because regulating action depends on core saturation, which reduces efficiency. The output waveform is heavily distorted unless careful measures are taken to prevent this. Saturating transformers provide a simple rugged method to stabilize an AC power supply.
Ferrite core[edit]
Ferrite core power transformers are widely used in switched-mode power supplies (SMPSs). The powder core enables high-frequency operation, and hence much smaller size-to-power ratio than laminated-iron transformers.
Ferrite transformers are not used as power transformers at mains frequency since laminated iron cores cost less than an equivalent ferrite core.
Planar transformer[edit]
A planar transformer
Exploded view: the spiral primary "winding" on one side of the PCB (the spiral secondary "winding" is on the other side of the PCB)
Manufacturers etch spiral patterns on a printed circuit board to form the "windings" of a planar transformer, replacing the turns of wire used to make other types. Some planar transformers are commercially sold as discrete components. Other planar transformers are one of many components on a printed circuit board. A planar transformer can be thinner than other transformers, which is useful for low-profile applications or when several printed circuit boards are stacked.[6] Almost all planar transformers use a ferrite planar core.
Oil cooled transformer[edit]
Large transformers used in power distribution or electrical substations have their core and coils immersed in oil, which cools and insulates. Oil circulates through ducts in the coil and around the coil and core assembly, moved by convection. The oil is cooled by the outside of the tank in small ratings, and by an air-cooled radiator in larger ratings. Where a higher rating is required, or where the transformer is in a building or underground, oil pumps circulate the oil, and an oil-to-water heat exchanger may also be used.[7] Some transformers may contain PCBs where or when its use was permitted. For example, until 1979 in South Africa.[8][9] substitute fire-resistant liquids such as silicone oils are now used instead.
Cast resin transformer[edit]
Cast-resin power transformers encase the windings in epoxy resin. These transformers simplify installation since they are dry, without cooling oil, and so require no fire-proof vault for indoor installations. The epoxy protects the windings from dust and corrosive atmospheres. However, because the molds for casting the coils are only available in fixed sizes, the design of the transformers is less flexible, which may make them more costly if customized features (voltage, turns ratio, taps) are required.[10][11]
Isolating transformer[edit]
An isolation transformer links two circuits magnetically, but provides no metallic conductive path between the circuits. An example application would be in the power supply for medical equipment, when it is necessary to prevent any leakage from the AC power system into devices connected to a patient. Special purpose isolation transformers may include shielding to prevent coupling of electromagnetic noise between circuits, or may have reinforced insulation to withstand thousands of volts of potential difference between primary and secondary circuits.
Instrument transformer[edit]
Main article: Instrument transformer
Instrument transformers
Instrument transformers are typically used to operate instruments from high voltage lines or high current circuits, safely isolating measurement and control circuitry from the high voltages or currents. The primary winding of the transformer is connected to the high voltage or high current circuit, and the meter or relay is connected to the secondary circuit. Instrument transformers may also be used as an isolation transformer so that secondary quantities may be used without affecting the primary circuitry.[12]
Terminal identifications (either alphanumeric such as H1, X1, Y1, etc. or a colored spot or dot impressed in the case) indicate one end of each winding, indicating the same instantaneous polarity and phase between windings. This applies to both types of instrument transformers. Correct identification of terminals and wiring is essential for proper operation of metering and protective relay instrumentation.
Current transformer[edit]
Main article: Current transformer
Current transformers used in metering equipment for three-phase 400 ampere electricity supply
A current transformer (CT) is a series connected measurement device designed to provide a current in its secondary coil proportional to the current flowing in its primary. Current transformers are commonly used in metering and protective relays in the electrical power industry.
Current transformers are often constructed by passing a single primary turn (either an insulated cable or an uninsulated bus bar) through a well-insulated toroidal core wrapped with many turns of wire. The CT is typically described by its current ratio from primary to secondary. For example, a 1000:1 CT provides an output current of 1 amperes when 1000 amperes flow through the primary winding. Standard secondary current ratings are 5 amperes or 1 ampere, compatible with standard measuring instruments. The secondary winding can be single ratio or have several tap points to provide a range of ratios. Care must be taken to make sure the secondary winding is not disconnected from its low-impedance load while current flows in the primary, as this may produce a dangerously high voltage across the open secondary and may permanently affect the accuracy of the transformer.
Specially constructed wideband CTs are also used, usually with an oscilloscope, to measure high frequency waveforms or pulsed currents within pulsed power systems. One type provides a voltage output that is proportional to the measured current. Another, called a Rogowski coil, requires an external integrator in order to provide a proportional output.
A current clamp uses a current transformer with a split core that can be easily wrapped around a conductor in a circuit. This is a common method used in portable current measuring instruments but permanent installations use more economical types of current transformer.
Voltage transformer or potential transformer[edit]
Voltage transformers (VT), also called potential transformers (PT), are a parallel connected type of instrument transformer, used for metering and protection in high-voltage circuits or phasor phase shift isolation. They are designed to present negligible load to the supply being measured and to have an accurate voltage ratio to enable accurate metering. A potential transformer may have several secondary windings on the same core as a primary winding, for use in different metering or protection circuits. The primary may be connected phase to ground or phase to phase. The secondary is usually grounded on one terminal.
There are three primary types of voltage transformers (VT): electromagnetic, capacitor, and optical. The electromagnetic voltage transformer is a wire-wound transformer. The capacitor voltage transformer uses a capacitance potential divider and is used at higher voltages due to a lower cost than an electromagnetic VT. An optical voltage transformer exploits the electrical properties of optical materials.[13] Measurement of high voltages is possible by the potential transformers.
Combined instrument transformer[edit]
Combined instrument transformer
A combined instrument transformer encloses a current transformer and a voltage transformer in the same transformer. There are two main combined current and voltage transformer designs: oil-paper insulated and SF6 insulated.[14] One advantage of applying this solution is reduced substation footprint, due to reduced number of transformers in a bay, supporting structures and connections as well as lower costs for civil works, transportation and installation.[15]
Pulse transformer[edit]
Bothhand TS6121A pulse transformer
A pulse transformer is a transformer that is optimised for transmitting rectangular electrical pulses (that is, pulses with fast rise and fall times and a relatively constant amplitude). Small versions called signal types are used in digital logic and telecommunications circuits, often for matching logic drivers to transmission lines. Medium-sized power versions are used in power-control circuits such as camera flash controllers. Larger power versions are used in the electrical power distribution industry to interface low-voltage control circuitry to the high-voltage gates of power semiconductors. Special high voltage pulse transformers are also used to generate high power pulses for radar, particle accelerators, or other high energy pulsed power applications.[16]
To minimize distortion of the pulse shape, a pulse transformer needs to have low values of leakage inductance and distributed capacitance, and a high open-circuit inductance. In power-type pulse transformers, a low coupling capacitance (between the primary and secondary) is important to protect the circuitry on the primary side from high-powered transients created by the load. For the same reason, high insulation resistance and high breakdown voltage are required. A good transient response is necessary to maintain the rectangular pulse shape at the secondary, because a pulse with slow edges would create switching losses in the power semiconductors.
The product of the peak pulse voltage and the duration of the pulse (or more accurately, the voltage-time integral) is often used to characterise pulse transformers. Generally speaking, the larger this product, the larger and more expensive the transformer.
Pulse transformers by definition have a duty cycle of less than 0.5; whatever energy stored in the coil during the pulse must be "dumped" out before the pulse is fired again.
RF transformer[edit]
There are several types of transformer used in radio frequency (RF) work. Laminated steel is not suitable for RF.
Air-core transformer[edit]
These are used for high frequency work. The lack of a core means very low inductance. All current excites current and induces secondary voltage which is proportional to the mutual inductance.[17] Such transformers may be nothing more than a few turns of wire soldered onto a printed circuit board.
Ferrite-core transformer[edit]
Ferrite-core transformers are widely used in impedance matching transformers for RF, especially for baluns (see below) for TV and radio antennas. Many only have one or two turns.
Transmission-line transformer[edit]
For radio frequency use, transformers are sometimes made from configurations of transmission line, sometimes bifilar or coaxial cable, wound around ferrite or other types of core. This style of transformer gives an extremely wide bandwidth but only a limited number of ratios (such as 1:9, 1:4 or 1:2) can be achieved with this technique.
The core material increases the inductance dramatically, thereby raising its Q factor. The cores of such transformers help improve performance at the lower frequency end of the band. RF transformers sometimes used a third coil (called a tickler winding) to inject feedback into an earlier (detector) stage in antique regenerative radio receivers.
In RF and microwave systems, a quarter-wave impedance transformer provides a way of matching impedances between circuits over a limited range of frequencies, using only a length of transmission line. The line may be coaxial cable, waveguide, stripline or microstripline.
Balun[edit]
Main article: Balun
Baluns are transformers designed specifically to connect between balanced (non-grounded) and unbalanced (grounded) circuits. These are sometimes made from configurations of transmission line and sometimes bifilar or coaxial cable and are similar to transmission line transformers in construction and operation. Baluns can be designed to not only interface between balanced and unbalanced loads, but to additionally provide impedance matching between those load types.
IF transformer[edit]
Ferrite-core transformers are widely used in (intermediate frequency) (IF) stages in superheterodyne radio receivers. They are mostly tuned transformers, containing a threaded ferrite slug that is screwed in or out to adjust IF tuning. The transformers are usually canned (shielded) for stability and to reduce interference.
Audio transformer[edit]
Two speaker-level audio transformers in a tube amplifier are seen on the left. The power supply toroidal transformer is on right
Five audio transformers for various line level purposes. The two black boxes on the left contain 1:1 transformers for splitting signals, balancing unbalanced signals, or isolating two different AC ground systems to eliminate buzz and hum. The two cylindrical metal cases fit into octal sockets; each one contains a 1:1 line transformer, the first is rated at 600 ohms, the second is rated at 15,000 ohms. On the far right is a DI unit; its 12:1 transformer (with yellow insulation) changes a high impedance unbalanced input to a low impedance balanced output.
Audio transformers are those specifically designed for use in audio circuits to carry audio signal. They can be used to block radio frequency interference or the DC component of an audio signal, to split or combine audio signals, or to provide impedance matching between high impedance and low impedance circuits, such as between a high impedance tube (valve) amplifier output and a low impedance loudspeaker, or between a high impedance instrument output and the low impedance input of a mixing console. Audio transformers that operate with loudspeaker voltages and current are larger than those that operate at microphone or line level, which carry much less power. Bridge transformers connect 2-wire and 4-wire communication circuits.
Being magnetic devices, audio transformers are susceptible to external magnetic fields such as those generated by AC current-carrying conductors. "Hum" is a term commonly used to describe unwanted signals originating from the "mains" power supply (typically 50 or 60 Hz).[18] Audio transformers used for low-level signals, such as those from microphones, often include magnetic shielding to protect against extraneous magnetically coupled signals.
Audio transformers were originally designed to connect different telephone systems to one another while keeping their respective power supplies isolated, and are still commonly used to interconnect professional audio systems or system components, to eliminate buzz and hum. Such transformers typically have a 1:1 ratio between the primary and the secondary. These can also be used for splitting signals, balancing unbalanced signals, or feeding a balanced signal to unbalanced equipment. Transformers are also used in DI boxes to convert high-impedance instrument signals (e.g., bass guitar) to low impedance signals to enable them to connect to a microphone input on the mixing console.
A particularly critical component is the output transformer of a valve amplifier. Valve circuits for quality reproduction have long been produced with no other (inter-stage) audio transformers, but an output transformer is needed to couple the relatively high impedance (up to a few hundred ohms depending upon configuration) of the output valve(s) to the low impedance of a loudspeaker. (The valves can deliver a low current at a high voltage; the speakers require high current at low voltage.) Most solid-state power amplifiers need no output transformer at all.
Audio transformers affect the sound quality because they are non-linear. Harmonic distortion is added to the original signal, especially odd-order harmonics with an emphasis on third-order harmonics. When the incoming signal amplitude is very low there is not enough level to energize the magnetic core (see coercivity and magnetic hysteresis). When the incoming signal amplitude is very high the transformer saturates and adds ringing harmonics.[19] Another non-linearity comes from limited frequency response. For good low-frequency response a relatively large magnetic core is required; high power handling increases the required core size. Good high-frequency response requires carefully designed and implemented windings without excessive leakage inductance or stray capacitance. All this makes for an expensive component.
Early transistor audio power amplifiers often had output transformers, but they were eliminated as advances in semiconductors allowed the design of amplifiers with sufficiently low output impedance to drive a loudspeaker directly.
Loudspeaker transformer[edit]
Loudspeaker transformer in old radio
In the same way that transformers create high voltage power transmission circuits that minimize transmission losses, loudspeaker transformers can power many individual loudspeakers from a single audio circuit operated at higher than normal loudspeaker voltages. This application is common in public address applications. Such circuits are commonly referred to as constant-voltage speaker systems. Such systems are also known by the nominal voltage of the loudspeaker line, such as 25-, 70- and 100-volt speaker systems (the voltage corresponding to the power rating of a speaker or amplifier). A transformer steps up the output of the system's amplifer to the distribution voltage. At the distant loudspeaker locations, a step-down transformer matches the speaker to the rated voltage of the line, so the speaker produces rated nominal output when the line is at nominal voltage. Loudspeaker transformers commonly have multiple primary taps to adjust the volume at each speaker in steps.
Output transformer[edit]
Valve (tube) amplifiers almost always use an output transformer to match the high load impedance requirement of the valves (several kilohms) to a low impedance speaker
Small signal transformer[edit]
Moving coil phonograph cartridges produce a very small voltage. For this to be amplified with a reasonable signal-noise ratio usually requires a transformer to convert the voltage to the range of the more common moving-magnet cartridges.
Microphones may also be matched to their load with a small transformer, which is mumetal shielded to minimise noise pickup. These transformers are less widely used today, as transistorized buffers are now cheaper.
Interstage and coupling transformers[edit]
In a push–pull amplifier, an inverted signal is required and can be obtained from a transformer with a center-tapped winding, used to drive two active devices in opposite phase. These phase splitting transformers are not much used today.
Other types[edit]
This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2013) (Learn how and when to remove this template message)
Transactor[edit]
A transactor is a combination of a transformer and a reactor. A transactor has an iron core with an air-gap, which limits the coupling between windings.[20]
Hedgehog[edit]
Hedgehog transformers are occasionally encountered in homemade 1920s radios. They are homemade audio interstage coupling transformers.
Enamelled copper wire is wound round the central half of the length of a bundle of insulated iron wire (e.g., florists' wire), to make the windings. The ends of the iron wires are then bent around the electrical winding to complete the magnetic circuit, and the whole is wrapped with tape or string to hold it together.
Variometer and variocoupler[edit]
Variometer used in 1920s radio receiver
A variometer is a type of continuously variable air-core RF inductor with two windings.[21] One common form consisted of a coil wound on a short hollow cylindrical form, with a second smaller coil inside, mounted on a shaft so its magnetic axis can be rotated with respect to the outer coil. The two coils are connected in series. When the two coils are collinear, with their magnetic fields pointed in the same direction, the two magnetic fields add, and the inductance is maximum. If the inner coil is rotated so its axis is at an angle to the outer coil, the magnetic fields do not add and the inductance is less. If the inner coil is rotated so it is collinear with the outer coil but their magnetic fields point in opposite directions, the fields cancel each other out and the inductance is very small or zero. The advantage of the variometer is that inductance can be adjusted continuously, over a wide range. Variometers were widely used in 1920s radio receivers. One of their main uses today is as antenna matching coils to match longwave radio transmitters to their antennas.
The vario-coupler was a device with similar construction, but the two coils were not connected but attached to separate circuits. So it functioned as an air-core RF transformer with variable coupling. The inner coil could be rotated from 0° to 90° angle with the outer, reducing the mutual inductance from maximum to near zero.
The pancake coil variometer was another common construction used in both 1920s receivers and transmitters. It consists of two flat spiral coils suspended vertically facing each other, hinged at one side so one could swing away from the other to an angle of 90° to reduce the coupling. The flat spiral design served to reduce parasitic capacitance and losses at radio frequencies.
Pancake or "honeycomb" coil vario-couplers were used in the 1920s in the common Armstrong or "tickler" regenerative radio receivers. One coil was connected to the detector tube's grid circuit. The other coil, the "tickler" coil was connected to the tube's plate (output) circuit. It fed back some of the signal from the plate circuit into the input again, and this positive feedback increased the tube's gain and selectivity.
Rotary transformer[edit]
Main article: Rotary transformer
A rotary (rotatory) transformer is a specialized transformer that couples electrical signals between two parts that rotate in relation to each other—as an alternative to slip rings, which are prone to wear and contact noise. They are commonly used in helical scan magnetic tape applications.
Variable differential transformer[edit]
Main articles: Linear variable differential transformer and rotary variable differential transformer
A variable differential transformer is a rugged non-contact position sensor. It has two oppositely-phased primaries which nominally produce zero output in the secondary, but any movement of the core changes the coupling to produce a signal.
Resolver and synchro[edit]
Main articles: Resolver (electrical) and synchro
The two-phase resolver and related three-phase synchro are rotary position sensors which work over a full 360°. The primary is rotated within two or three secondaries at different angles, and the amplitudes of the secondary signals can be decoded into an angle. Unlike variable differential transformers, the coils, and not just the core, move relative to each other, so slip rings are required to connect the primary.
Resolvers produce in-phase and quadrature components which are useful for computation. Synchros produce three-phase signals which can be connected to other synchros to rotate them in a generator/motor configuration.
See also[edit]
Three-phase
Three-phase electric power
Buck–boost transformer
Tap changer
Transformer
Motor-generator
References[edit]
Jump up ^ "The basics of autotransformers". ECMwebs.
Jump up ^ Donald G. Fink & H. Wayne Beatty. (1978). Standard Handbook for Electrical Engineers, 11th Edition. McGraw Hill, ISBN 0-07-020974-X pp. 10–44 and 10–45.
Jump up ^ T. J. Gallagher and A. J. Pearmain (1983): "High Voltage - Measurement, Testing and Design", ISBN 0-471-90096-6
Jump up ^ "3-Phase Step-Up Transformer", Agile Magnetics, Retrieved June 8, 2016.
Jump up ^ Philips PM3311 Oscilloscope service manual Section 6.2.16 [describing the switch mode power supply],"The unregulated d.c. voltage is applied in the form of pulses to a resonant transformer T1602..."
Jump up ^ "Planar Transformer on a PCB"
Jump up ^ ANSI IEEE Standard C57.12.00 General Requirements for Liquid-Immersed Distribution, Power and Regulating Transformers, 2000
Jump up ^ page 9
Jump up ^ UNEP Chemicals (1999). Guidelines for the Identification of PCBs and Materials Containing PCBs (PDF). United Nations Environment Programme. p. 2. Retrieved 2007-11-07.
Jump up ^ [1]
Jump up ^ [2]
Jump up ^ "Measurement Canada Standard Dwg. No.3400 D3 Delta Connected CTs" (PDF). MEASUREMENT CANADA. Retrieved 12 December 2012.
Jump up ^ Network Protection & Automation, AREVA 2002
Jump up ^ "The combined transformer - an optimal solution för HV substations, p. 1" (PDF). Retrieved 9 July 2013.
Jump up ^ "Combined instrument transformer, PVA 123, p. 2" (PDF). Retrieved 9 July 2013.
Jump up ^ Khanchandani, M.D. Singh, K.B. (2008). Power electronics (2nd ed.). New Delhi: Tata McGraw-Hill. p. 76. ISBN 9780070583894.
Jump up ^ "Air Core Transformers", Virtual Institute of Applied Science, Retrieved June 8, 2016
Jump up ^ Rumsey, Francis; McCormick, Tim (2009). Sound and recording (6th ed.). Oxford, UK: Focal Press. p. 356. ISBN 978-0-240-52163-3.
Jump up ^ Robjohns, Hugh (February 2010). "Analogue Warmth – The Sound Of Tubes, Tape & Transformers". Sound On Sound.
Jump up ^ The Institution of Engineering and Technology (1995). Power system protection. London: Institution of Electrical Engineers. ISBN 0852968361.
Jump up ^ Douglas, Alan (1995). Radio manufacturers of the 1920's. Chandler, Ariz.: Sonoran Pub. p. 76. ISBN 9781886606005.
[hide]
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Transformer
Types
Amorphous metal transformer
Austin transformer
Autotransformer
Buck–boost transformer
Capacitor voltage transformer
Current transformer
Distribution transformer
Delta-wye transformer
Energy efficient transformer
Flyback transformer
Grounding transformer
Instrument transformer
Isolation transformer
Dry Isolation transformer
Linear variable differential transformer
Modulation transformer
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Padmount transformer
Paraformer
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Rotary transformer
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Scott-T transformer
Trigger transformer
Variable-frequency transformer
Zigzag transformer
Coils
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Topics
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Prolec GE
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Severity factor
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Toroidal inductors and transformers
Transformer oil
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