US2991437A - Magnetic core - Google Patents

Description

J. KREUZER ETAL July 4, 1961 MAGNETIC CORE 2 Sheets-Sheet 1 Filed Sept. 18, 1956 INVENTOR5 ATT RNEY5 July 4, 1961 J. KREUzl-:R ET AL MAGNETIC CORE 2 Sheets-Sheet 2 Filed Sept. 18, 1956 l INVENTORS Jsejf zffaazer 14.50% e7;

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ATT RNEYS 2,991,437 f MAGNETIC CORE yJosef Kreuzer and Otto Ascher, Graz, Austria,

to` Elin Aktiengesellschaft fr Elektrische lndustrie,

Vienna, Austria, a iointstock corporation of Austria t Filed Sept. '18, 1956, Ser. No. 610,524 Claims priority, application Austria Sept. 20, 1955 2 Claims. ('Cl. 336-5) .This invention relates to magnetic core structures for use in electrical induction apparatus such as transformers f and reactors.

The necessity for installing in one transformer unit `more and more power without exceeding the dimensional limits imposed by railroad transportation led, in single- United States .ice

phase transformers, from the two-leg-core to the fourleg-core'land, in three-phase transformers, from the threeleg-core to the ve-leg-core. The outer legs may'then also be wound. In such cases, the circumstance, that the outer legs have rectangular cross sections, is a considerable disadvantage, because the coils placed on the outer legs must be wound oval, and therefore tively small short-circuit strength.

It is an object of this invention to provide a structure fora transformer or 4reactor core having n main` legs possess only rela- (n 2 2) and two outer legs, `the latter having an approxi# vmately round cross section with a diameter smaller than ,the diameter of a main leg, and connecting yokes the FIG. 3 `is one half (section a in FIG. 1).

FIG. 4 is one half of a section through a main yoke (section in FIG; l);

FIG. 5 is one half of a section through an outer yoke (section y in FIG. 11) and FIG. 6 is one half of a section through an outer leg (section in FIG. 1).

IAlthough not wishing to conne this invention to magnetic cores stacked of cold-rolled sheets, having therefore a greater permeability land lesser watt losses per unit volume when the ow of tlux is through the steel in the direction of rolling than when it is through the core in other direction, it is, however, assumed for purposes of illustration that the core be built up of a high grade steel, and is extensively subdivided by cooling ducts of a sec'atio-nY through a main leg running parallel to or at right angles with the planes of 6 the laminae.

As is seen from FIG. 2 the magnetic core consists of (n-|--2)\-leg core, where n=2 the layers of which have everywhere the same height d1=c1=a1=b1. On both sides of the n main legs 1 and 2 there are added further stacks of sheets 9 and 10 each having a height of layer a2. The cross section of the main legs is completed in this approximately a full circle. The stacks are closed to a full two-leg magnetic circuit by yokes 6, 7, and 8 of a height of layer b2 (in which b2=a2). The diameter of the resulting cross section of a main leg is indicated in FIG. 2, Iby D, the dameter of the outer legs, 3 and 4 by d.

`letweengthe layers with the '2,991,437 lPatented July 4, 196.1

2 height b1 and the layers with the height bala cooling duct 11 is provided.

In-FIG. 3, the Abreadth of sheets forming one bundle Vvof `laminae of a main leg of the (n+2) -leg core is indicated by that of the further stacks of sheets 9 and `10 of a main leg of the core by t r 2 The second half of the sectional area may be thoughtK to be specularlysymmetrical.

Likewse, lin FIG.- 4, 5 and 6 the breadth of sheets forming one bundle of laminae of the main yoke 6, the outer yokes 7 and 8 and the outer leg belonging to the (n4-2) leg core are indicated by 2oV -B-x- Cx and the breadth of sheets forming one bundle of further laminae of the yoke 6 connecting the main legs of the core is indicated by The diameter of the main legs and the outer legs is indicated again by D and d. As is to 'be seen from the FIGURES 4 and 5, also the main yoke and the outer yoke possess cooling ducts running at right angles to the 'plane of' lamination, The-breadth of all sheetsy lying in series in the direction of the magnetic ux is the same, that is, according to reference letters of FIGURES 3-6 en@ ma azie lTherefore, also, the staggering of the bundle of lamina- FIG. 2 is a transverse sectionthrough the legs of a corel*o i' according to FIG. 1;

tionslying-in seriesin the direction of the magnetic flux isthe same and the resultingfcore possesses simplev and clear lines' f orthe magnetic flux also in its corne-rs andi equal induction in all bundles of laminations of the legs and of the yokes. The advantages connected with these features of the magnetic core according to this invention are obvious especially if high grade steel is used. The hollows which occur in the outer legs when the above postulate is fulfilled may be used for cooling. The maximum height connecting the yoke of the main legs of the core amounts to half :the diameter of amain leg By dividing the total core in suitable manner into the (n-i-Z) -leg core and the two-leg cores there is attained o that also for exact equal induction in each bundle of laminae is not to be observed rigorously, but-there-may-be deviation from it by reducing .the number of steps of the yokcs (of the main yokes and of theJouter yokes) and of the outer such a case the height of Sheetsfor one bundle oflar'nin'ae of a yoke or an outer legmay'amountto the average of lapped laminated one. The yokesfand legs may also be 'butt-jointed. The use 'of the'miteredjoint isalso pj'os'sible and advantageous especially yif the core is stacked'of high grade Steel sheets.

The advantages of a core according to this invention are essentially as follows. 'lt is an 'easily andtherefore inexpensively manufactura-ble magnetic core with' favorable; guidance for the magnetic ilux. yThemainflegsand `also the outer legsfpossess circular cross section and-the height of the yokes is reduced to half the main legldiarneter. VApart from the miteredajoint-modicationall `sheets show rectangular shape. They mayitherefore be manufactured only by lcutting and need no stamping methods leaving waste material and causing burrs. Each bundle of laminae of the legs end of the yokes has the same induction and undergoes therefore also-'equal-Iheating. The guidance of the magnetic flux isgclearr also in the corners and branching points forthe magnetic lines and there is no cause fon-additional iron-losses. The advantages for fthe yoke piessure are mentioned above.

Y At flast,"as the sheets are all Stackedfin parallel; 'no` bend ing-'or buckling is` required which-'would-cause considerable deterioration of the: iron-lossesf-'per funit `volume especially with `cold-rolled sheets.

laminae forming an approximately circularrcrossese'ction t'ofV a'diameter smaller'than the diameteriofsaidz'main legs, said main'legs each Ybeing-comprised 'of'a central stack of laminae having the'same'height of layer as the "the-height-of the two main leg steps lying in series for g ythe main legs to approximately a-full circle, said central 4 outer legs and being Yflanked on opposite sides from a common` plane through the center lines of the-'mainvand outer legs by further stacks of laminae completing the cross-section of the main legs -to approximately a full circle, said central stacks of laminae of the main legs and the stacks of laminaeiothe outer legs being combined 4by said yoke portions"to"rst closed magnetic circuits;thefstacksofilamnae anki'ng themain legs 'heilig cuitslyingfparallel Ato saidrst magnetic circuits, respectively, the-laminae ofall stacks of the '-legs-and-theyoke portions lying inseries'for'the magnetic flux lines having the same breadth.

'2.A 'laminated magnetic core eomprising'at leastf two outer'legs, two- 1'main legs A'audyokei 'portions closing the magnetic circuits between said main legs andsaidv outer legs respectively, lsaid outer legs being comprised of said main legs and having centrally situated hollows, the

beingflanked onopposite sides from aV common: plane through the' center linesv of the main andouter :legs by further stacks `of laminae completing the-crosS-sectionof stacks of laminae of the 'main legsand said'staeksfof Alaminae of the outer legs respectively, being combined Y'by yoke portionshto closed magneticcircuits,Y the-stacks `of laminae flanking the Amain legs being closed by' further V`yoke portions to further magnetic circuits lying parallel kto theI irst magnetic circuits respectively, the laminae of all stacks of the legs and the yoke portions lying in" series lforthe'magnetic ux linesfhaving the same lbreadth.

l References -Cted inthe le ofthis' patent UNITED STATES PATENTS Y, 41,425,0911 Horelick l .Aug."8,"l922 `2,761,407 Kane Aug. 28, 1956 12,779,926 Johnson et al. 'zlan.-29,' 1957 2,780,786 "Johnson Feb. 7, v17957 j FOREIGN PATENTS 230,571 Switzerland Apre l, jr19114

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