CA1075784A - Reactor core - Google Patents
Reactor coreInfo
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- CA1075784A CA1075784A CA276,326A CA276326A CA1075784A CA 1075784 A CA1075784 A CA 1075784A CA 276326 A CA276326 A CA 276326A CA 1075784 A CA1075784 A CA 1075784A
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- core
- legs
- air gaps
- end plates
- laminations
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Abstract
REACTOR CORE
Abstract of the Disclosure A reactor core includes a plurality of laminations of trapezoidal shape forming the legs of the core. These legs are arranged in generally rectangular configuration with air gaps provided at the comers of the core. These air gaps extend diagonally of the core legs and are formed between the inclined faces of adjacent ends of the trapezoidal-shaped core legs. End plates each having a longitudinal section extending parallel to and fixed to one of the legs and having flanges at each end of the longitudinal section extending perpendicularly to the longitudinal section are provided for maintaining the legs of the core in assembled relation and for effecting adjustment of the air gaps. The end plates include elongated openings in the flanges thereof for permitting movement of each of the end plates, and the leg to which it is affixed, relative to the remainder of the core for varying the size of the diagonal air gaps. A plurality of metallic, non-magnetic spacers having substantially the same shape as the end plates are disposed at intervals between the end plates to separate the core laminations into groups. These spacers carry the magnetic forces tending to close the air gap. Fastening devices extend through the elongated openings and are loosened to permit movement of the end plate and its associated leg relative to adjacent legs for changing the size of the air gaps and then again tightened to hold the legs in the adjusted position. The fastening devices are accessible from the exterior of the reactor to facilitate convenient adjustment of the air gaps. Because of the separation of the laminations into groups to reduce the forces necessary to oppose magnetic forces tending to close the air gaps and also, due to the diagonal construction of the air gaps, which has the effect of reducing the flux density and therefore themagnetic force at the air gaps the fastening devices can be designed to maintain the legs in adjusted position without the need of air gaps blocking spacers in the air gaps. The air gaps, therefore, are available as passages for the flow of cooling gas for removal of heat from the reactor core.
Abstract of the Disclosure A reactor core includes a plurality of laminations of trapezoidal shape forming the legs of the core. These legs are arranged in generally rectangular configuration with air gaps provided at the comers of the core. These air gaps extend diagonally of the core legs and are formed between the inclined faces of adjacent ends of the trapezoidal-shaped core legs. End plates each having a longitudinal section extending parallel to and fixed to one of the legs and having flanges at each end of the longitudinal section extending perpendicularly to the longitudinal section are provided for maintaining the legs of the core in assembled relation and for effecting adjustment of the air gaps. The end plates include elongated openings in the flanges thereof for permitting movement of each of the end plates, and the leg to which it is affixed, relative to the remainder of the core for varying the size of the diagonal air gaps. A plurality of metallic, non-magnetic spacers having substantially the same shape as the end plates are disposed at intervals between the end plates to separate the core laminations into groups. These spacers carry the magnetic forces tending to close the air gap. Fastening devices extend through the elongated openings and are loosened to permit movement of the end plate and its associated leg relative to adjacent legs for changing the size of the air gaps and then again tightened to hold the legs in the adjusted position. The fastening devices are accessible from the exterior of the reactor to facilitate convenient adjustment of the air gaps. Because of the separation of the laminations into groups to reduce the forces necessary to oppose magnetic forces tending to close the air gaps and also, due to the diagonal construction of the air gaps, which has the effect of reducing the flux density and therefore themagnetic force at the air gaps the fastening devices can be designed to maintain the legs in adjusted position without the need of air gaps blocking spacers in the air gaps. The air gaps, therefore, are available as passages for the flow of cooling gas for removal of heat from the reactor core.
Description
~0757~
REACTOR CORE
Backqround of the Invention Field of the Invention This lnvention relates to reactor cores, for example cores for reactors used with rotating dynamoelectric machines, and more S particularly to core clamplng and air gap arrangements for su~h reactor cores.
Description of the Prior Art The prior art discloses many examples of reactor cores com-po~ed of a plurality of laminations and in many cases havinçJ one or more air gaps arranged therein. Such reactor cores usually include a plurality of legs and the air gap or gaps are arranged in one or more of these legs. The gap is normally provided by spaced faces perpendicular , to the leg ln which the gap ls located. The prior art also includes arrangements for ad~usting the size of the gap to vary the reactance of the reactor of which the core is a part.
Such reactors may be used for example in connection with dynamoelectric machines. In this type of use such a reactor may be employed in serles with each of the legs of a primary winding of an -~
excitation transformer,the secondary of which may be in circuit with an SCR for controlling the fleld excitation of the dynamoelectric machine;
for example, lt may be used in a circuit such as that shown ln U.S.Patent 3,702,965, assigned to the assignee of the present lnvention.
Partlcularly in such uses lnvolvlng relatively large currents the reactor core may have substantial magnetic flux therethrough and j 25 this flux tends to move the parts of the core on opposi~e sides of an ., ad~ustable alr ~ap toward each other wlth substantial force. In order ~0757~3~
to counteract the effect of thls force and malntain the deslred alr gap, some prlor art structures have employed spacers of non-metallic material in the air gap which block the same.
However, such cores are also subject to development of substantial heat therein and it is necessary to circulate cooling gas through the core to effect removal of this excess heat. One convenient path for flow of such gas to remove excess heat is through the air gaps in the core but the inclusion of the aforementioned spacers blocks, or at least partially obstructs, the flow of gas, thereby reducing the cooling effectiveness. Additionally, such spacers cannot be relied upon, under heavy-duty conditions over a long period of time, as for .. : .
example the uninterrupted operating cycle of an electric utility generator which may run for years without shutdown, to adequately perform the air gap maintenance function. ~ such installations with large air gaps lntense heat ls generated. Mechanical spacers are susceptible, under such conditions over such time periods, to deterioration and change of di~nenslon. This can lead to clearances and loosening of the spacers, whiCh in turn can lead to vlbratlon of the magnetic parts, wear, and eventual fallure of the reactor.
Moreover, the extent of cooling is also affected by the extent of the surface area of the opposed faces on opposite sides of the air gaps. In the usual prior art structure the gap has been formed so that tbese faces are perpendicular to the core leg and the surface area is therefore limited to the cross-sectional area o~ the leg. In accordance with the present invention the gap is formed to extend diagonally of the core leg thereby materially increasing the surface area of the faces on oppo~lte slde~ of the gap and hence incrsaslng the surface contacted
REACTOR CORE
Backqround of the Invention Field of the Invention This lnvention relates to reactor cores, for example cores for reactors used with rotating dynamoelectric machines, and more S particularly to core clamplng and air gap arrangements for su~h reactor cores.
Description of the Prior Art The prior art discloses many examples of reactor cores com-po~ed of a plurality of laminations and in many cases havinçJ one or more air gaps arranged therein. Such reactor cores usually include a plurality of legs and the air gap or gaps are arranged in one or more of these legs. The gap is normally provided by spaced faces perpendicular , to the leg ln which the gap ls located. The prior art also includes arrangements for ad~usting the size of the gap to vary the reactance of the reactor of which the core is a part.
Such reactors may be used for example in connection with dynamoelectric machines. In this type of use such a reactor may be employed in serles with each of the legs of a primary winding of an -~
excitation transformer,the secondary of which may be in circuit with an SCR for controlling the fleld excitation of the dynamoelectric machine;
for example, lt may be used in a circuit such as that shown ln U.S.Patent 3,702,965, assigned to the assignee of the present lnvention.
Partlcularly in such uses lnvolvlng relatively large currents the reactor core may have substantial magnetic flux therethrough and j 25 this flux tends to move the parts of the core on opposi~e sides of an ., ad~ustable alr ~ap toward each other wlth substantial force. In order ~0757~3~
to counteract the effect of thls force and malntain the deslred alr gap, some prlor art structures have employed spacers of non-metallic material in the air gap which block the same.
However, such cores are also subject to development of substantial heat therein and it is necessary to circulate cooling gas through the core to effect removal of this excess heat. One convenient path for flow of such gas to remove excess heat is through the air gaps in the core but the inclusion of the aforementioned spacers blocks, or at least partially obstructs, the flow of gas, thereby reducing the cooling effectiveness. Additionally, such spacers cannot be relied upon, under heavy-duty conditions over a long period of time, as for .. : .
example the uninterrupted operating cycle of an electric utility generator which may run for years without shutdown, to adequately perform the air gap maintenance function. ~ such installations with large air gaps lntense heat ls generated. Mechanical spacers are susceptible, under such conditions over such time periods, to deterioration and change of di~nenslon. This can lead to clearances and loosening of the spacers, whiCh in turn can lead to vlbratlon of the magnetic parts, wear, and eventual fallure of the reactor.
Moreover, the extent of cooling is also affected by the extent of the surface area of the opposed faces on opposite sides of the air gaps. In the usual prior art structure the gap has been formed so that tbese faces are perpendicular to the core leg and the surface area is therefore limited to the cross-sectional area o~ the leg. In accordance with the present invention the gap is formed to extend diagonally of the core leg thereby materially increasing the surface area of the faces on oppo~lte slde~ of the gap and hence incrsaslng the surface contacted
-2-,, .
~075784 by the cooling gas flowing through the gap to remove heat from the core.
The force tending to urge the parts of the reactor core on opposite sides of the gap toward each other is deperldent upon the S flux density at the gap. With prior art structures In whlch the ~ap ls made so that ~e face~ are perpendicular to the leg of the core there ls a substantial flux density and hence a substantial force whlch has to be counteracted in order to maintain the gap at its desired size.
With the diagonal air gap arrangement of the present invention the surface area at the gap is materially increased and the flux density across the gap for a given flux density in the reactor core is corre- -spondingly reduced, thereby reducing the force whlch must be counter-acted in maintaining the gap size.
In such reactor cores it is desirable to provide means for ad~usting the size of the gap in order to vary the reactance of the reactor oi whlch the core is a part. In accordance with the present invention the ad~ustment ls conveniently made by simply loosening fastening means accesslble from the exterior of the reactor core making the desired adjustment and then tightenlng the fastening means to hold the parts ln the adjusted posltion. Moreover, the aforementioned dlagonal gap provides "flne tuning" in facilitatins~ accurate ad~ustment of the gap.
Accordingly, it is a principal ob~sct of the invention to provide lamlnated core struature for lnductlve devlces whlch has greater support in opposltion to magnetic forces than was heretofore avallable.
It 18 another object of the present inventlon to provide a reactor oore havlng an improved arrangement for adjustln~ an air gap
~075784 by the cooling gas flowing through the gap to remove heat from the core.
The force tending to urge the parts of the reactor core on opposite sides of the gap toward each other is deperldent upon the S flux density at the gap. With prior art structures In whlch the ~ap ls made so that ~e face~ are perpendicular to the leg of the core there ls a substantial flux density and hence a substantial force whlch has to be counteracted in order to maintain the gap at its desired size.
With the diagonal air gap arrangement of the present invention the surface area at the gap is materially increased and the flux density across the gap for a given flux density in the reactor core is corre- -spondingly reduced, thereby reducing the force whlch must be counter-acted in maintaining the gap size.
In such reactor cores it is desirable to provide means for ad~usting the size of the gap in order to vary the reactance of the reactor oi whlch the core is a part. In accordance with the present invention the ad~ustment ls conveniently made by simply loosening fastening means accesslble from the exterior of the reactor core making the desired adjustment and then tightenlng the fastening means to hold the parts ln the adjusted posltion. Moreover, the aforementioned dlagonal gap provides "flne tuning" in facilitatins~ accurate ad~ustment of the gap.
Accordingly, it is a principal ob~sct of the invention to provide lamlnated core struature for lnductlve devlces whlch has greater support in opposltion to magnetic forces than was heretofore avallable.
It 18 another object of the present inventlon to provide a reactor oore havlng an improved arrangement for adjustln~ an air gap
-3-.
~07S784 therein .
It is still another o~bject of this invention to provide a reactor core which requires no spacers in the air gap thereby leaving an unobstructed passage for flow of cooling gas.
It is a further object of this invention to provide a reactor core having an air gap arranged in a manner which reduces flux density across the gap and thereby reduces the force tending to urge the faces of the core leg on opposite sides of the gap toward each other.
It is still a further object of this invention to provide an air gap arranged so as to maximize the cooling surface provided by the gap.
It is a further ob~ect of this invention to provide an adjustable air gap arranged so as to achieve "fine tunin~" in the ad~llstment of the gap, It ls a further ob~ect of this inventlon to provide slmple and èffective means accessible from the exterior of the core for effecting ad~ustment of the air gap.
Sum~arY of the Invention The reactor core of this invention, in one form thereof, includes a plurality of laminations of magnetic matetlal of trapezoidal shape arranged so as to form a reactor core component of generally rectangular or square configuration. The trapezoldal shape of the laminations forming the legs of the core provides air gaps at the comers which extend dlagonally of the legs. End plates havlng a longitudinal section eoctending parallel to and fixed to the laminations forming one of the legs and `
flanges at each end thereof extending perpendicularly to the longitudinal section are provided for maintaining the legs of the core in assembled nlatlon~hlp and for effectlng ad~u8tment oi the alr ~ap~. Specifically, ' ' . ' ' `'.
~075784 each end plate includes openings in the longitudinal section aligned with corresponding openings in a first leg of the core for receiving fastenlng devices to hold the end plate and the laminations of the flrst leg in firm, fixed relationship. The end plate includes ln each of its flanges an elongated opening, each elongated openlng extending in the direction of the corresponding one of the core legs adjacent to the first le~. Fastening devices extend through these elongated openings and corresponding aligned openings in the ad~acent legs.
The elongated openings permit the end plate and the first leg to be mc~ved relative to the adjacent legs for adjustlng the size of the air gaps between the ends of the first leg and the adjacent leg. A similar end plate is provided at the opposite slde of the core for effecting variation in the size of the air gaps at the other corners of the core.
Finally, and of ma~or importance, in order to distribute shear forces between adjacent laminations and between end laminations and the end plates spacers of non-magnetic metallic material corresponding in shape to the shape of the aforementioned end plates are employed at intervals between groups of laminations to carry the magnetic forces tending to close the air gap. Because of the foregoing structural features of the reactor core for providing improved support against deformation by magnetic forces, no spacers need be employed between ad~acent legs of the core, and the air gaps, therefore, provide unobstructed pas~ages for the flow of gas for cooling the reactor core.
Additionally, the same structure provides for ad~ustment of the air gaps of the core for optimum magnetic reluctance characteristlcs.
Brief Descri~tion of the Drawinas FIGURE 1 i~ a perspective viaw of a reactor inaorporating the . ' . . ' , ~ ~ , ' - ~ .
reactor core construction of this invention.
FIGURE 2 is a perspective view, partially exploded, of a -~ portion of the reactor core of Flgure l showlng details of the con-struction.
FIGURE 3 is a partial perspective view of one comer of a reactor core in accord with the invention illustrating one air gap, ad~acent laminations and the relationship of the end plates and supporting spacers thereto.
FIGURE 4 is a simplifled schematic illustration of components of the reactor core for purposes of illustrating the manner of adjust-ment of the air gap.
FIGURE 5 is a view of an end plate employed in the reactor core construction of this invention, and FIGURE 6 is an enlarged view of one comer of the reactor.
lS Descrl~tlon of the Preferred Embodiment Referring to FIGURES 1, 2 and 3, illustratlng one form of thls invention, there is shown a reactor including a core generally deslgnated by the numeral 10. The core lncludes a plurallty of thin lamlnatlons 12 of magnetlc materlal having thlcknesses of the order of O.OlO to 0.015 inch whlch are stacked to form legs of the desired thi¢knass. The laminatlons are held in assembled relationship to form the core by means of relatlvely thlck (approxlmately 0.50 inch, for example) end plates 14. A plurallty of fastenlng means, which in the form shown are bolts 16, are employed for holding the end plates and 2S the lamlnations forming the legs of the core structure in assembledrelationshlp. Bolts 16, assoclated with nuts ~ot shown), extelld through aligned openin~s ln ~he end plates and in the laminated legs of ~'' .
1075'78~
the core, each bolt and nut engaging end plates placed on opposlte sldes of the stacks of lamlnations for pressing the lamlnatlons and the end plates in firm, frictional assembled relationshlp. Spacers 18 of non-magnetic metalllc material and correspondlng in shape to the end plates, and having a thickness large as compared with the lamlnations 12, e.g., approximately 0.125 inch, for example, are employed at spaced intervals between groups of stacked lamlnatlons.
A coil 20 encircles the central portion of the reactor core to complete the basic structure of the reactor.
Referring particularly to FIGURE 2, each of the laminations whlch, ln stacked form, make up the indlvidual legs of the core 10 are of trapezoidal shape, as indicated at 22. Each of the laminatlons of trapezoidal shape includes a plurality of openings 24 which are arranged for allgnment wlth corresponding openings 26 in the spacers and end plates. The bolts 16 extend through these aligned openings.
The general arrangement of the legs which make up the reactor core is best shown in the schematic illustration ln FIGURE 4. As there shown, ln the preferred embodiment of thls lnventlon, the core ls speciflcally formed of elght legs of stacked laminatlons arranged in two slde-by-slde core components, each composed of four such legs. For convenlence in later descrlptlon, the legs shown in FIGURE 4 are deslgnated by the numerals 28, 30, 32 and 34 fonning one core component and by numerals 36, 38, 40 and 42 formlng the second core component. The ad~acent legs are assembled wlth the inclined ;
ends of the trapezoids faolng each other, thereby provlding at ends of , ad~acent leg~ air gap~ 44 extending diagonally of the core legs. The c~verall ~tructure comprlfilng the two core comPonent~ a~ ~hown in , :
.~ . , : . : : , -. :: .
.. . . . . - . .
FIGURE 4, has the appearance of two rectangular core elements ln slde-by-slde relatlonehlp, The ad~acent le~s 34 and 38 of the two - core component~ are a~Tanged in parallel ~paced relatlonshlp toprovlde a passage 46 for flow of ~as therethrou~h to a~sl~t ln removlng heat from the reactor core.
In accord wlth the present lnventlon, unlque and effectlve means are utlllzed to provlde a core as generally descrlbed hereln-before havlng unblocked dlagonal alr gaps whlch are ad~u~table and of great importance ln whlch the core structure ls well supported to reslst the magnetlc forces whlch tend to change the alr gaps.
In regard to supportlng the core strueture, ln lleu of the spacers or blocks lnserted lnto the alr gap ln accord wlth the prlor art, we rely upon compression of the lamlnatlons to~ether between the - respectlve end plates ln order to produce frlctlonal forces between ad~acent lamlnatlons and end platefi sufflclent to oppose the magnetlc forces seeklng to draw the laminatlons together across the alr gap.
Slnce, however, the compresslve force whlch ls applled to create the opposlng frlctlonal (or shear) force ls llmlted by requlrements of avoldlng deformatlon, the mechanlcal strength of the compresslve means and other factors, we lnterpose a plurallty of non-magnetic spacer~ 18 at approprlate lntervals between end plates 14 to separate the lamlnatlons 12 into a plurallty of groups 13 of laminatlons, preferably of equal thlckness, each of whlch 18 sub~ected to a fractlon of the : ~ ~
;1, ma~netlc forces across the entire gap. Thus in the absence of spacer~
18, lf a magnetlo force of 12,000 pounds was applled bythe magnetlc flwc to draw the lamlnatlons together and close the alr gap and reduce the magnetio reluctance of ~he flux path, a compre~slble force ~ufflclent ..
~ , .' ' . .
-~0757~3~
l 7GE-24 80 to establish a frictional force of 12,000 pounds would be required to prevent deformation of the gap. Since the distrlbutlon of shear forces in such a situation places a maximum force of approxlmately half the total force between eac:h end plate and its ad~acent laminatlon, the compressive force would, in the absence of spacers, have to be sufficient to establish a frictlonal force of 6, 000 pounds at each such interface, with lesser forces applied to successive interiaces, and approaching zero force at the center of the lamination stack.
Since the spacers 18 bridge the gaps 44, the required com-presslve force to oppose the magnetic force ls only a fraction of the total magnetlc force. For example, lf flve spacers 18 are utillzed, separating the laminatlons lnto slx groups 13, then the compresslve force requlred to prevent distortlon of the core need only be that sufflolent-to produce a maximum frlctional force of l,000 pounds between ad~acent laminatlons and end plates. Since the same frictlonal force exists throughout the laminated core, the necessary compressive -force ls reduced by a factor equal to the number of spacers utllized plus one (or the number of groups of lamination~ establlshed).
In further accordance with the present lnventlon, a simple and effective arrangement is provided for varying the size of some or all of the air gaps to ad~ust the reactance of the reactor. This is provided by employing end plates ~of approprlate configuration and employing elongated openings at particular portions of these end plates. Since . ~ ~ , . .
~; the spacers, thU8 employed, are of the same general shape, but of :~
lesser thickness, and utilize openlngs of the same corlfiguration and positlonlng as those ln the end plates, reference ls made in the following descriptlon to FlGURE 2 whlch lllustrates spacers and .
_g_ ',, .
- , ~ , :, ~075784 FIGURE 5 which illustrates an end plate (brackets and ears on the end plates, as shown in FIGURE l, have been omltted ln FIGURE 5 for simplicity) and the same numerals have been applied to corre-sponding openings in the spacers and end plates. Referring now to FIGURES 2 and 5, each end plate 14 (and spacer lF~) is formed of a generally E-shape (except that the E has two central elements), and includes a longitudinal section 48 and a plurality of flanges 50 extending perpendicularly to the longitudinal section 48. A plurality of openings, previously designated by the numerals 26, are formed in the longitudinal section, these openings, as also previously lndicated, belng arranged for alignment with corresponding openings 24 ln the laminatlons of trapezoidal shape. In addition one or more elongated openings 52 are forrned in each of the flanges 50 of the end plates 14 and of the spacers 18. These elongated openings permit relative move-1~ ment between the end plates and the legs of the core associated with the flanges of the end plates so as to vary the slze of the alr gaps as ~:~ deslred.
In provlding for assembly of the elements to form the core and to provlde for ad~ustmentof the alr gap, a palr of end plates 14, one on the top and one on the bottom of the stack of laminatlons, are assembled to legs 28 and 36 and fastened in fixed relation thereto by `~ fastenlng devlces or bolts 16 extending through aligned openings 24 in the trapezoldal-shaped laminatlons and openlngs 26 in the end plates ~¦ and ln the spacers 18 therebetween. When the bolts are tightened the "~
end plates and the laminatlons formlng the legs 28 and 36 are assembled In firm, flxed frlctlonal relatlonshlp, adequately bound to prevent ' dl~tortlon of the alr gap~.
, ~: `
. ~. , ., .. . ~ . . .
1075~78~
Legs 30, 34, 38 and 42 are arranged, as shown ln FIGURE 4, extending perpendicularly to and spaced from the legs 28 and 36 to form air gaps 44 at the corners of the core components. This assembly is effected by fastening devices, such as bolts designated by 54 in S FIGURE 1, which extend through elongated openings 52 in the end plates and spacers and also through aligned openings 24 in the trapezoidal-shaped laminations forming the legs 30, 34, 38 and 42.
Similar end plates are employed on the opposlte longitudinal side of the core and are similarly arranged in engagement wi~ longitudinally extending legs 32 and 40 and perpendicularly related legs 30, 34, 38 and 42.
The elongated openings provide for movement of the end plates relative to the perpendicularly arranged legs 30, 34, 38 and 42, such movement, as limited by the elongated openings, being in the direction in which these legs extend, that is in a veItical direction in FIGURE 4.
Such movement provides for varying the slze of the air gaps. Referring particularly to FIGURE 4, the legs 28 and 36 in their solid llne positlons, as shown in that figure, are spaced from corresponding perpendicularly extending legs to provide air gaps 44 having a dimension indicated by d.
If it i8 desired to ad~ust the air gaps at the lower corners of the core to provide a larger dimension d', the bolts 54 connecting the end plates and the perpendicularly extending legs 30, 34, 38 and 42 are loosened.
The elongated slots then permit movement of the end plates 14 together with the legs 28 and 36 fixed thereto in the direction of the arrows 56 -~
to the dotted line position indicated by the numeral 58. As indicated ;
in FIGURE 4, this movement increaseæ the dimension of the air gaps at all four lower comer~ from the original dlmen~ion d to the larger . .
dlmension d', thereby varying the reactance of the reactor by the desired amount. The bolts 54 are then tightened, presslng the end plates, the laminations of the legs 30, 34, 38 and 42 and the spacers therebetween into firm frictional engagement for maintaining the legs ln the adjusted position and hence for maintaining the ad~usted air gaps.
Ad~ustment of the d~agonal air gaps at the upper corners of the core structure shown in FIGURE 4 is simllarly effected by loosening the bolts 54 which hold the upper end plates and the perpendicularly extending legs 30, 34, 38 and 42 in assembled relationship, moving these end plates and the associated legs 32 and 40 to the desired ad~usted position to establlsh the desired air gap and then tlghtenlng the bolts to hold the elements in assembled relatlonship. In the core structure of this invention, as can be seen in FIGURE 1, the bolts 54 are accessible from the exterior of the assembled reactor so that ad~ustment of the air gaps may be conveniently and easlly effected exteriorly of the reactor.
It will be apparent that while the embodiment illustrated includes two slde-by-side core components each formed of four legs arranged ln a generally rectangular, or more speclfically square, conflguratlon and whlle thls ls the embodlment speclfically utlllzed in connectlon with the use of the reactor in certain dynamoelectric machines, ~ .
other uses may be satisfled by employlng only one of the side-by-side core companents, for example a core component includlng only legs 2~8, 30, 32 and 34. Moreover, while in the embodiment lllustrated and i 25 described, lt ~8 contemplated that adjustment will be provlded for all '~ elght air gaps, it may be sufficient ~n some applications to provide for ad~ù~tment of only some of the alr ~aps, for example those at the bottom : . :
~075784 17GE-2480 corners; ln this case only the legs 28 and 36 would be moved, leaving the legs 32 and 40 in a fixed non-adjustable posltion. If a slngle core component were employed, lt would also be possible to limlt the ad~ustment, for example, to the single leg 28, thereby varying only the tWQ air gaps adjacent the ends of this leg. It would also be possible in some applications to make the legs 30, 32 and 34, for example, in a single unitary assembly or with the legs abutting ~o that no air gaps would be provided at the upper comers, leaving only ad~ustable air gaps at the lower corners. Finally, if desired only a single air gap could be employed. For example, the leg 28 could be arranged to abut the leg 34 providing only a gap at the right corner between legs 28 and 30. In that case ad~ustment would have to be effected by moving the leg 28 diagonally along abutting faces of the legs 28 and 34 to vary the air gap. If thls last-described construction were employed, the elongated openings would have to be in line with - the diagonal abutting faces of the legs 28 and 34 rather than in a vertical direction as illustrated in the embodiment described.
Thus, while there has been descrlbed in detail a preferred embodiment of the lnv~tlon which i8 utilized in dynamoelectric machines, it wlll be apparent that numerous modifications can be made in the partlcular structure dependirlg on the reactance requirements and the degree of adJustment thereof which is considered necessary in a partlcular application .
In addition to the ease of ad~ustment of the air gap, the core 2S structure of this invention provides additional advantages ~ecause of the particular arrangement of the air gap employed ~erein. One such advantage can be~t be understood by con~iderlng ~hat the force between '~
two magnetic surfaces tending to move the surfaces toward each other may be stated by the formula F-.01387~ lbs./sq. in.
where F is the force and P~ is the flux density at the alr gap in S KL/sq. in. In reactors such as those employed in connection with large dynamoelectric machines can be quite large. For example, where ~ is 100 KI/in.2 P from the above formula would be 139 pounds per s~uare inch. If the cross-sectional area of the air gap in a particular application is, for example, six inches by twelve inches or 72 square inches, the total force at the air gap would be approxi-mately 10, 000 pounds . This force, of course, must be opposed by the frictional engagement of the end plates and the laminations forming the legs of the core, the force causing the frictional resistance being provided by the fastening devices such as the bolts 16 and 54. The conventional method of opposing such forces to insure maintenance of the air gap ls to place insulating spacers ln the gaps to take the magnetic force in compression. However, it ls convenient to employ the air gaps as passages for the flow of gas to effect removal of heat from the reactor, thls heat in applications such as dynamoelectric machines being substantial because of the hlgh currents flowing through the coil of the reactor. Insulating spacers in the gaps, however, tend to reduce or obstruct the flow of cooling gas through these passages and hence materlally reduce or eliminate the effectiveness of such gaps for cooling purposes.
In accordance with the present invention these air gaps are ~ maintalned unobstructed, due to the interposition of non-magnetic i metalllc ~pacer~ whlch brldge the air gas~s and sepaFate the laminations , ~ --14~
~' . ~ ` `
, ~075 784 17GE-2480 of the core into groups,eac~ of which 15 required to be sub~ect2d to a significantly lesser compressive force to produce frictlonal (or shear) forces sufficlent to oppose the magnetic forces tending to draw the laminations together and close the air gaps. The necessary com-pressive force is further reduced by the location and size of the air çjaps herein. Where, as in conven~ional prior art d0vices, the air gaps are formed transversely of the individual legs, for example, where a conventional E-core structure is employed, the ilwc density across the air gap corresponds to that in the core legs. In the structure of the present invention, however, the air gaps are specifically arranged diagonally of the legs thereby provlding a materially greater surface.
This correspondingly reduces the flux density across the air gap to a substantially lesser magnitude than that in conventional structures where the air gap extends transversely of the core legs. For example, considering the structure illustrated in FIGURE 4 where the air gap extends at the 45 angle relative to the ad~acent legs, the surface of the air gap is~times the surface available where a conventional air gap extending transversely of one of ths legs is employed. This corre-spondingly reduces the flux density ~, . Since the force, as indicated by the above formula, vari0s as the square of the flux density the force per square inch with the structure of this invention will be 1/2 that of a conventional transversely ~xtending air gap. Since the area is greater --by the ratio of ~, the actual reduction ln total force tending to move the lags toward each other in the structure of this invention will be in the ratio f V~ compared to the force in a transversely extending air gap with the same cro~s section of core leg. In other words, the total force at the air ~ap in the core structure of thls inventicn i6 approximately .~' - . :: - . .. . - . . . . .. .. ... . - .......... --: - . - . ~: .. - . . .
. .
1075'78~
7/10 of that encountered in conven~ional structures. Since, as indicated in the above illustration, this iorce with conventional structures may be in the order of 10,000 pounds the force would be reduced, in the applicants' structure, to 7,000 pounds. This corre-S spondingly reduces the force which must be exerted to achieve the frictional relationship adequate to counteract this magnetic force and enables us to provide for maintenance of the established air gap with-out the need for utilization of insulating spacers which could interfere with or block flow of cooling gas through the passages provided by the alr gaps. Thus, as shown in FIGURE 5 and more clearly in the enlarged view of FIGURE 6, there is an unobstructed path between adjacent legs, for example, legs 40 and 42 in FIGURE 6, for flow of cooling gas in the direction of the arrows 60 through the alr gap to remove heat from the core in that area and then around the coil 20. In practice, the reactor would normally be enclosed wlthin a gas-tight casing and cooling gas would be directed by suitable gas circulating means through the passages provided by the air gaps. The cooling gas would, for example, be directed to the extreme corners of the core structure, as shown in FIGURE 4 and flow in the general dlrection of the arrows 60. In additlon to flowing through the alr gaps and around the coll 20, cooling gas also passes through the passage 46 provided between the spaced central legs 34 and 38 of the core structure.
In addltlon to achleving unobstructed passages for flow of coollng gas through the alr gaps, the diagonal air gap provides a greater surface area to be contacted by the cooling gas and hence more effectlve heat removal.
In additlon to the advantage~ already discu~sed, the diagonal '- - . ' . .
~07578~
air gap arrangement of our core structure also provides "fine tuning"
in the ad~ustment of the air gap. This can be most clearly seen by refsrence to FIGURE 6 which shows an enlarged vlew of a portion of the core structure. In FIGURE 6 the leg 40 is shown in solid lines in position wherein the air gap has a dimension dl and in a dotted line position where the air gap has a larger dimension d2. The change in the size of the air gap resulting from the movement of the leg 40 from its solid line position to its dotted line position is therefore measured by d2-dl, that is the dimension indicated by the designation d3 ln FIGURE 6.
To effect thls change in the size of the air gap, the leg 40 has been moved in the direction of the arrow 62 by an amount indicated by the dimension D3. It can be readily seen by visual comparison of the dimensions D3 and d3 that the movement of the leg 40 for effecting this adjustment of the air gap is significantly greater than ~e change in the size of the air gap itself. In the arrangement shown in FIGURE 6, since the air gap is at a 45 angle the distance D3 is ~times the distance d3. Since the change in the dlmension of the air gap is, therefore, less than the movement of the leg 40 by thls ratio, a "finer tuning" in the ad~ustment of the air gap can be achieved.
Finally, it can also be seen by reference to FIGURE 6 that the ; reduction in the magnetlc material of the core leg caused by the presence of the opening8 for the bolts 16 therein is less where the gaps are placed diagonally at the comers, as in the applicants' invention, than where openings for receiving fastenlng devices are placed transversely of the core leg in the conventional constructlon for holding lamlnations in a~8embled relatlonshlp.
iO7S784 17GE-2480 While a particular reactor core construction has been shown and described as utilized in the use of the reactor with large dynamo-electric maehines, other modifications, some of which have been discussed earlier in this specification, wlll occur to those skilled S in the art. It is intended, therefore, that the invention not be limited to the particular embodiments shown and described and that the appended claims should eover such modifications as fall within the spirit and scope thereof.
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~07S784 therein .
It is still another o~bject of this invention to provide a reactor core which requires no spacers in the air gap thereby leaving an unobstructed passage for flow of cooling gas.
It is a further object of this invention to provide a reactor core having an air gap arranged in a manner which reduces flux density across the gap and thereby reduces the force tending to urge the faces of the core leg on opposite sides of the gap toward each other.
It is still a further object of this invention to provide an air gap arranged so as to maximize the cooling surface provided by the gap.
It is a further ob~ect of this invention to provide an adjustable air gap arranged so as to achieve "fine tunin~" in the ad~llstment of the gap, It ls a further ob~ect of this inventlon to provide slmple and èffective means accessible from the exterior of the core for effecting ad~ustment of the air gap.
Sum~arY of the Invention The reactor core of this invention, in one form thereof, includes a plurality of laminations of magnetic matetlal of trapezoidal shape arranged so as to form a reactor core component of generally rectangular or square configuration. The trapezoldal shape of the laminations forming the legs of the core provides air gaps at the comers which extend dlagonally of the legs. End plates havlng a longitudinal section eoctending parallel to and fixed to the laminations forming one of the legs and `
flanges at each end thereof extending perpendicularly to the longitudinal section are provided for maintaining the legs of the core in assembled nlatlon~hlp and for effectlng ad~u8tment oi the alr ~ap~. Specifically, ' ' . ' ' `'.
~075784 each end plate includes openings in the longitudinal section aligned with corresponding openings in a first leg of the core for receiving fastenlng devices to hold the end plate and the laminations of the flrst leg in firm, fixed relationship. The end plate includes ln each of its flanges an elongated opening, each elongated openlng extending in the direction of the corresponding one of the core legs adjacent to the first le~. Fastening devices extend through these elongated openings and corresponding aligned openings in the ad~acent legs.
The elongated openings permit the end plate and the first leg to be mc~ved relative to the adjacent legs for adjustlng the size of the air gaps between the ends of the first leg and the adjacent leg. A similar end plate is provided at the opposite slde of the core for effecting variation in the size of the air gaps at the other corners of the core.
Finally, and of ma~or importance, in order to distribute shear forces between adjacent laminations and between end laminations and the end plates spacers of non-magnetic metallic material corresponding in shape to the shape of the aforementioned end plates are employed at intervals between groups of laminations to carry the magnetic forces tending to close the air gap. Because of the foregoing structural features of the reactor core for providing improved support against deformation by magnetic forces, no spacers need be employed between ad~acent legs of the core, and the air gaps, therefore, provide unobstructed pas~ages for the flow of gas for cooling the reactor core.
Additionally, the same structure provides for ad~ustment of the air gaps of the core for optimum magnetic reluctance characteristlcs.
Brief Descri~tion of the Drawinas FIGURE 1 i~ a perspective viaw of a reactor inaorporating the . ' . . ' , ~ ~ , ' - ~ .
reactor core construction of this invention.
FIGURE 2 is a perspective view, partially exploded, of a -~ portion of the reactor core of Flgure l showlng details of the con-struction.
FIGURE 3 is a partial perspective view of one comer of a reactor core in accord with the invention illustrating one air gap, ad~acent laminations and the relationship of the end plates and supporting spacers thereto.
FIGURE 4 is a simplifled schematic illustration of components of the reactor core for purposes of illustrating the manner of adjust-ment of the air gap.
FIGURE 5 is a view of an end plate employed in the reactor core construction of this invention, and FIGURE 6 is an enlarged view of one comer of the reactor.
lS Descrl~tlon of the Preferred Embodiment Referring to FIGURES 1, 2 and 3, illustratlng one form of thls invention, there is shown a reactor including a core generally deslgnated by the numeral 10. The core lncludes a plurallty of thin lamlnatlons 12 of magnetlc materlal having thlcknesses of the order of O.OlO to 0.015 inch whlch are stacked to form legs of the desired thi¢knass. The laminatlons are held in assembled relationship to form the core by means of relatlvely thlck (approxlmately 0.50 inch, for example) end plates 14. A plurallty of fastenlng means, which in the form shown are bolts 16, are employed for holding the end plates and 2S the lamlnations forming the legs of the core structure in assembledrelationshlp. Bolts 16, assoclated with nuts ~ot shown), extelld through aligned openin~s ln ~he end plates and in the laminated legs of ~'' .
1075'78~
the core, each bolt and nut engaging end plates placed on opposlte sldes of the stacks of lamlnations for pressing the lamlnatlons and the end plates in firm, frictional assembled relationshlp. Spacers 18 of non-magnetic metalllc material and correspondlng in shape to the end plates, and having a thickness large as compared with the lamlnations 12, e.g., approximately 0.125 inch, for example, are employed at spaced intervals between groups of stacked lamlnatlons.
A coil 20 encircles the central portion of the reactor core to complete the basic structure of the reactor.
Referring particularly to FIGURE 2, each of the laminations whlch, ln stacked form, make up the indlvidual legs of the core 10 are of trapezoidal shape, as indicated at 22. Each of the laminatlons of trapezoidal shape includes a plurality of openings 24 which are arranged for allgnment wlth corresponding openings 26 in the spacers and end plates. The bolts 16 extend through these aligned openings.
The general arrangement of the legs which make up the reactor core is best shown in the schematic illustration ln FIGURE 4. As there shown, ln the preferred embodiment of thls lnventlon, the core ls speciflcally formed of elght legs of stacked laminatlons arranged in two slde-by-slde core components, each composed of four such legs. For convenlence in later descrlptlon, the legs shown in FIGURE 4 are deslgnated by the numerals 28, 30, 32 and 34 fonning one core component and by numerals 36, 38, 40 and 42 formlng the second core component. The ad~acent legs are assembled wlth the inclined ;
ends of the trapezoids faolng each other, thereby provlding at ends of , ad~acent leg~ air gap~ 44 extending diagonally of the core legs. The c~verall ~tructure comprlfilng the two core comPonent~ a~ ~hown in , :
.~ . , : . : : , -. :: .
.. . . . . - . .
FIGURE 4, has the appearance of two rectangular core elements ln slde-by-slde relatlonehlp, The ad~acent le~s 34 and 38 of the two - core component~ are a~Tanged in parallel ~paced relatlonshlp toprovlde a passage 46 for flow of ~as therethrou~h to a~sl~t ln removlng heat from the reactor core.
In accord wlth the present lnventlon, unlque and effectlve means are utlllzed to provlde a core as generally descrlbed hereln-before havlng unblocked dlagonal alr gaps whlch are ad~u~table and of great importance ln whlch the core structure ls well supported to reslst the magnetlc forces whlch tend to change the alr gaps.
In regard to supportlng the core strueture, ln lleu of the spacers or blocks lnserted lnto the alr gap ln accord wlth the prlor art, we rely upon compression of the lamlnatlons to~ether between the - respectlve end plates ln order to produce frlctlonal forces between ad~acent lamlnatlons and end platefi sufflclent to oppose the magnetlc forces seeklng to draw the laminatlons together across the alr gap.
Slnce, however, the compresslve force whlch ls applled to create the opposlng frlctlonal (or shear) force ls llmlted by requlrements of avoldlng deformatlon, the mechanlcal strength of the compresslve means and other factors, we lnterpose a plurallty of non-magnetic spacer~ 18 at approprlate lntervals between end plates 14 to separate the lamlnatlons 12 into a plurallty of groups 13 of laminatlons, preferably of equal thlckness, each of whlch 18 sub~ected to a fractlon of the : ~ ~
;1, ma~netlc forces across the entire gap. Thus in the absence of spacer~
18, lf a magnetlo force of 12,000 pounds was applled bythe magnetlc flwc to draw the lamlnatlons together and close the alr gap and reduce the magnetio reluctance of ~he flux path, a compre~slble force ~ufflclent ..
~ , .' ' . .
-~0757~3~
l 7GE-24 80 to establish a frictional force of 12,000 pounds would be required to prevent deformation of the gap. Since the distrlbutlon of shear forces in such a situation places a maximum force of approxlmately half the total force between eac:h end plate and its ad~acent laminatlon, the compressive force would, in the absence of spacers, have to be sufficient to establish a frictlonal force of 6, 000 pounds at each such interface, with lesser forces applied to successive interiaces, and approaching zero force at the center of the lamination stack.
Since the spacers 18 bridge the gaps 44, the required com-presslve force to oppose the magnetic force ls only a fraction of the total magnetlc force. For example, lf flve spacers 18 are utillzed, separating the laminatlons lnto slx groups 13, then the compresslve force requlred to prevent distortlon of the core need only be that sufflolent-to produce a maximum frlctional force of l,000 pounds between ad~acent laminatlons and end plates. Since the same frictlonal force exists throughout the laminated core, the necessary compressive -force ls reduced by a factor equal to the number of spacers utllized plus one (or the number of groups of lamination~ establlshed).
In further accordance with the present lnventlon, a simple and effective arrangement is provided for varying the size of some or all of the air gaps to ad~ust the reactance of the reactor. This is provided by employing end plates ~of approprlate configuration and employing elongated openings at particular portions of these end plates. Since . ~ ~ , . .
~; the spacers, thU8 employed, are of the same general shape, but of :~
lesser thickness, and utilize openlngs of the same corlfiguration and positlonlng as those ln the end plates, reference ls made in the following descriptlon to FlGURE 2 whlch lllustrates spacers and .
_g_ ',, .
- , ~ , :, ~075784 FIGURE 5 which illustrates an end plate (brackets and ears on the end plates, as shown in FIGURE l, have been omltted ln FIGURE 5 for simplicity) and the same numerals have been applied to corre-sponding openings in the spacers and end plates. Referring now to FIGURES 2 and 5, each end plate 14 (and spacer lF~) is formed of a generally E-shape (except that the E has two central elements), and includes a longitudinal section 48 and a plurality of flanges 50 extending perpendicularly to the longitudinal section 48. A plurality of openings, previously designated by the numerals 26, are formed in the longitudinal section, these openings, as also previously lndicated, belng arranged for alignment with corresponding openings 24 ln the laminatlons of trapezoidal shape. In addition one or more elongated openings 52 are forrned in each of the flanges 50 of the end plates 14 and of the spacers 18. These elongated openings permit relative move-1~ ment between the end plates and the legs of the core associated with the flanges of the end plates so as to vary the slze of the alr gaps as ~:~ deslred.
In provlding for assembly of the elements to form the core and to provlde for ad~ustmentof the alr gap, a palr of end plates 14, one on the top and one on the bottom of the stack of laminatlons, are assembled to legs 28 and 36 and fastened in fixed relation thereto by `~ fastenlng devlces or bolts 16 extending through aligned openings 24 in the trapezoldal-shaped laminatlons and openlngs 26 in the end plates ~¦ and ln the spacers 18 therebetween. When the bolts are tightened the "~
end plates and the laminatlons formlng the legs 28 and 36 are assembled In firm, flxed frlctlonal relatlonshlp, adequately bound to prevent ' dl~tortlon of the alr gap~.
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1075~78~
Legs 30, 34, 38 and 42 are arranged, as shown ln FIGURE 4, extending perpendicularly to and spaced from the legs 28 and 36 to form air gaps 44 at the corners of the core components. This assembly is effected by fastening devices, such as bolts designated by 54 in S FIGURE 1, which extend through elongated openings 52 in the end plates and spacers and also through aligned openings 24 in the trapezoidal-shaped laminations forming the legs 30, 34, 38 and 42.
Similar end plates are employed on the opposlte longitudinal side of the core and are similarly arranged in engagement wi~ longitudinally extending legs 32 and 40 and perpendicularly related legs 30, 34, 38 and 42.
The elongated openings provide for movement of the end plates relative to the perpendicularly arranged legs 30, 34, 38 and 42, such movement, as limited by the elongated openings, being in the direction in which these legs extend, that is in a veItical direction in FIGURE 4.
Such movement provides for varying the slze of the air gaps. Referring particularly to FIGURE 4, the legs 28 and 36 in their solid llne positlons, as shown in that figure, are spaced from corresponding perpendicularly extending legs to provide air gaps 44 having a dimension indicated by d.
If it i8 desired to ad~ust the air gaps at the lower corners of the core to provide a larger dimension d', the bolts 54 connecting the end plates and the perpendicularly extending legs 30, 34, 38 and 42 are loosened.
The elongated slots then permit movement of the end plates 14 together with the legs 28 and 36 fixed thereto in the direction of the arrows 56 -~
to the dotted line position indicated by the numeral 58. As indicated ;
in FIGURE 4, this movement increaseæ the dimension of the air gaps at all four lower comer~ from the original dlmen~ion d to the larger . .
dlmension d', thereby varying the reactance of the reactor by the desired amount. The bolts 54 are then tightened, presslng the end plates, the laminations of the legs 30, 34, 38 and 42 and the spacers therebetween into firm frictional engagement for maintaining the legs ln the adjusted position and hence for maintaining the ad~usted air gaps.
Ad~ustment of the d~agonal air gaps at the upper corners of the core structure shown in FIGURE 4 is simllarly effected by loosening the bolts 54 which hold the upper end plates and the perpendicularly extending legs 30, 34, 38 and 42 in assembled relationship, moving these end plates and the associated legs 32 and 40 to the desired ad~usted position to establlsh the desired air gap and then tlghtenlng the bolts to hold the elements in assembled relatlonship. In the core structure of this invention, as can be seen in FIGURE 1, the bolts 54 are accessible from the exterior of the assembled reactor so that ad~ustment of the air gaps may be conveniently and easlly effected exteriorly of the reactor.
It will be apparent that while the embodiment illustrated includes two slde-by-side core components each formed of four legs arranged ln a generally rectangular, or more speclfically square, conflguratlon and whlle thls ls the embodlment speclfically utlllzed in connectlon with the use of the reactor in certain dynamoelectric machines, ~ .
other uses may be satisfled by employlng only one of the side-by-side core companents, for example a core component includlng only legs 2~8, 30, 32 and 34. Moreover, while in the embodiment lllustrated and i 25 described, lt ~8 contemplated that adjustment will be provlded for all '~ elght air gaps, it may be sufficient ~n some applications to provide for ad~ù~tment of only some of the alr ~aps, for example those at the bottom : . :
~075784 17GE-2480 corners; ln this case only the legs 28 and 36 would be moved, leaving the legs 32 and 40 in a fixed non-adjustable posltion. If a slngle core component were employed, lt would also be possible to limlt the ad~ustment, for example, to the single leg 28, thereby varying only the tWQ air gaps adjacent the ends of this leg. It would also be possible in some applications to make the legs 30, 32 and 34, for example, in a single unitary assembly or with the legs abutting ~o that no air gaps would be provided at the upper comers, leaving only ad~ustable air gaps at the lower corners. Finally, if desired only a single air gap could be employed. For example, the leg 28 could be arranged to abut the leg 34 providing only a gap at the right corner between legs 28 and 30. In that case ad~ustment would have to be effected by moving the leg 28 diagonally along abutting faces of the legs 28 and 34 to vary the air gap. If thls last-described construction were employed, the elongated openings would have to be in line with - the diagonal abutting faces of the legs 28 and 34 rather than in a vertical direction as illustrated in the embodiment described.
Thus, while there has been descrlbed in detail a preferred embodiment of the lnv~tlon which i8 utilized in dynamoelectric machines, it wlll be apparent that numerous modifications can be made in the partlcular structure dependirlg on the reactance requirements and the degree of adJustment thereof which is considered necessary in a partlcular application .
In addition to the ease of ad~ustment of the air gap, the core 2S structure of this invention provides additional advantages ~ecause of the particular arrangement of the air gap employed ~erein. One such advantage can be~t be understood by con~iderlng ~hat the force between '~
two magnetic surfaces tending to move the surfaces toward each other may be stated by the formula F-.01387~ lbs./sq. in.
where F is the force and P~ is the flux density at the alr gap in S KL/sq. in. In reactors such as those employed in connection with large dynamoelectric machines can be quite large. For example, where ~ is 100 KI/in.2 P from the above formula would be 139 pounds per s~uare inch. If the cross-sectional area of the air gap in a particular application is, for example, six inches by twelve inches or 72 square inches, the total force at the air gap would be approxi-mately 10, 000 pounds . This force, of course, must be opposed by the frictional engagement of the end plates and the laminations forming the legs of the core, the force causing the frictional resistance being provided by the fastening devices such as the bolts 16 and 54. The conventional method of opposing such forces to insure maintenance of the air gap ls to place insulating spacers ln the gaps to take the magnetic force in compression. However, it ls convenient to employ the air gaps as passages for the flow of gas to effect removal of heat from the reactor, thls heat in applications such as dynamoelectric machines being substantial because of the hlgh currents flowing through the coil of the reactor. Insulating spacers in the gaps, however, tend to reduce or obstruct the flow of cooling gas through these passages and hence materlally reduce or eliminate the effectiveness of such gaps for cooling purposes.
In accordance with the present invention these air gaps are ~ maintalned unobstructed, due to the interposition of non-magnetic i metalllc ~pacer~ whlch brldge the air gas~s and sepaFate the laminations , ~ --14~
~' . ~ ` `
, ~075 784 17GE-2480 of the core into groups,eac~ of which 15 required to be sub~ect2d to a significantly lesser compressive force to produce frictlonal (or shear) forces sufficlent to oppose the magnetic forces tending to draw the laminations together and close the air gaps. The necessary com-pressive force is further reduced by the location and size of the air çjaps herein. Where, as in conven~ional prior art d0vices, the air gaps are formed transversely of the individual legs, for example, where a conventional E-core structure is employed, the ilwc density across the air gap corresponds to that in the core legs. In the structure of the present invention, however, the air gaps are specifically arranged diagonally of the legs thereby provlding a materially greater surface.
This correspondingly reduces the flux density across the air gap to a substantially lesser magnitude than that in conventional structures where the air gap extends transversely of the core legs. For example, considering the structure illustrated in FIGURE 4 where the air gap extends at the 45 angle relative to the ad~acent legs, the surface of the air gap is~times the surface available where a conventional air gap extending transversely of one of ths legs is employed. This corre-spondingly reduces the flux density ~, . Since the force, as indicated by the above formula, vari0s as the square of the flux density the force per square inch with the structure of this invention will be 1/2 that of a conventional transversely ~xtending air gap. Since the area is greater --by the ratio of ~, the actual reduction ln total force tending to move the lags toward each other in the structure of this invention will be in the ratio f V~ compared to the force in a transversely extending air gap with the same cro~s section of core leg. In other words, the total force at the air ~ap in the core structure of thls inventicn i6 approximately .~' - . :: - . .. . - . . . . .. .. ... . - .......... --: - . - . ~: .. - . . .
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7/10 of that encountered in conven~ional structures. Since, as indicated in the above illustration, this iorce with conventional structures may be in the order of 10,000 pounds the force would be reduced, in the applicants' structure, to 7,000 pounds. This corre-S spondingly reduces the force which must be exerted to achieve the frictional relationship adequate to counteract this magnetic force and enables us to provide for maintenance of the established air gap with-out the need for utilization of insulating spacers which could interfere with or block flow of cooling gas through the passages provided by the alr gaps. Thus, as shown in FIGURE 5 and more clearly in the enlarged view of FIGURE 6, there is an unobstructed path between adjacent legs, for example, legs 40 and 42 in FIGURE 6, for flow of cooling gas in the direction of the arrows 60 through the alr gap to remove heat from the core in that area and then around the coil 20. In practice, the reactor would normally be enclosed wlthin a gas-tight casing and cooling gas would be directed by suitable gas circulating means through the passages provided by the air gaps. The cooling gas would, for example, be directed to the extreme corners of the core structure, as shown in FIGURE 4 and flow in the general dlrection of the arrows 60. In additlon to flowing through the alr gaps and around the coll 20, cooling gas also passes through the passage 46 provided between the spaced central legs 34 and 38 of the core structure.
In addltlon to achleving unobstructed passages for flow of coollng gas through the alr gaps, the diagonal air gap provides a greater surface area to be contacted by the cooling gas and hence more effectlve heat removal.
In additlon to the advantage~ already discu~sed, the diagonal '- - . ' . .
~07578~
air gap arrangement of our core structure also provides "fine tuning"
in the ad~ustment of the air gap. This can be most clearly seen by refsrence to FIGURE 6 which shows an enlarged vlew of a portion of the core structure. In FIGURE 6 the leg 40 is shown in solid lines in position wherein the air gap has a dimension dl and in a dotted line position where the air gap has a larger dimension d2. The change in the size of the air gap resulting from the movement of the leg 40 from its solid line position to its dotted line position is therefore measured by d2-dl, that is the dimension indicated by the designation d3 ln FIGURE 6.
To effect thls change in the size of the air gap, the leg 40 has been moved in the direction of the arrow 62 by an amount indicated by the dimension D3. It can be readily seen by visual comparison of the dimensions D3 and d3 that the movement of the leg 40 for effecting this adjustment of the air gap is significantly greater than ~e change in the size of the air gap itself. In the arrangement shown in FIGURE 6, since the air gap is at a 45 angle the distance D3 is ~times the distance d3. Since the change in the dlmension of the air gap is, therefore, less than the movement of the leg 40 by thls ratio, a "finer tuning" in the ad~ustment of the air gap can be achieved.
Finally, it can also be seen by reference to FIGURE 6 that the ; reduction in the magnetlc material of the core leg caused by the presence of the opening8 for the bolts 16 therein is less where the gaps are placed diagonally at the comers, as in the applicants' invention, than where openings for receiving fastenlng devices are placed transversely of the core leg in the conventional constructlon for holding lamlnations in a~8embled relatlonshlp.
iO7S784 17GE-2480 While a particular reactor core construction has been shown and described as utilized in the use of the reactor with large dynamo-electric maehines, other modifications, some of which have been discussed earlier in this specification, wlll occur to those skilled S in the art. It is intended, therefore, that the invention not be limited to the particular embodiments shown and described and that the appended claims should eover such modifications as fall within the spirit and scope thereof.
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Claims (4)
1. A laminated air-gap core for a high current reactor comprising:
a) first and second respective oppositely disposed pairs of core legs forming a rectangle, each of said core legs being of a trapezoidal shape so as to define with adjacent legs a plurality of diagonal air gaps devoid of any solid spacers at respective corners of said rectangle;
b) a pair of end plates disposed along opposite sides of each of said first oppositely disposed pair of core legs and extending at right angles therefrom so as to partially extend along the sides of each of said second pair of oppositely disposed core legs and extending across the gaps defined by adjacent core legs and engaging the planar edges of said core legs in flat abutting frictional relationship;
c) each of said core legs comprising:
c1) a plurality of very thin ferromagnetic laminations having said trapezoidal shape and being of a flat planar configuration both before assembly into said core and after assembly and compression therein;
c2) a plurality of thick planar non-magnetic spacer members having substantially the same shape as said end plates interposed at regular intervals within said core engaging said laminations in flat abutting frictional relationship and separating said laminations of said core legs into a plurality of lamination groups, said spacer members operating to change the pattern of shear-resisting forces applied between said laminations during operation of said reactor so as to reduce the maximum shear-resisting forces between any lamination and any adjacent planar surface by a factor equal to the number of lamination groups created by the interpositioning of said spacer members;
d) means applying a substantially uniform compressive force to each of said first pair of oppositely disposed pair of core legs to apply to the laminations and spacer members thereof a compressive force sufficient to compress said laminations without deformation of the same, said compressive force being sufficient to apply frictional forces between said laminations, said end plates and said spacer members to resist the maximum shear force caused by electrical phenomena during operation of said reactor and tending to close or deform said air gaps;
e) means applying a substantially uniform compressive force to each of said second pair of oppositely disposed pair of core legs to apply thereto a compressive force sufficient to establish without deformation of said laminations an equivalent frictional force as is applied to each of said first oppositely disposed pair of core legs.
a) first and second respective oppositely disposed pairs of core legs forming a rectangle, each of said core legs being of a trapezoidal shape so as to define with adjacent legs a plurality of diagonal air gaps devoid of any solid spacers at respective corners of said rectangle;
b) a pair of end plates disposed along opposite sides of each of said first oppositely disposed pair of core legs and extending at right angles therefrom so as to partially extend along the sides of each of said second pair of oppositely disposed core legs and extending across the gaps defined by adjacent core legs and engaging the planar edges of said core legs in flat abutting frictional relationship;
c) each of said core legs comprising:
c1) a plurality of very thin ferromagnetic laminations having said trapezoidal shape and being of a flat planar configuration both before assembly into said core and after assembly and compression therein;
c2) a plurality of thick planar non-magnetic spacer members having substantially the same shape as said end plates interposed at regular intervals within said core engaging said laminations in flat abutting frictional relationship and separating said laminations of said core legs into a plurality of lamination groups, said spacer members operating to change the pattern of shear-resisting forces applied between said laminations during operation of said reactor so as to reduce the maximum shear-resisting forces between any lamination and any adjacent planar surface by a factor equal to the number of lamination groups created by the interpositioning of said spacer members;
d) means applying a substantially uniform compressive force to each of said first pair of oppositely disposed pair of core legs to apply to the laminations and spacer members thereof a compressive force sufficient to compress said laminations without deformation of the same, said compressive force being sufficient to apply frictional forces between said laminations, said end plates and said spacer members to resist the maximum shear force caused by electrical phenomena during operation of said reactor and tending to close or deform said air gaps;
e) means applying a substantially uniform compressive force to each of said second pair of oppositely disposed pair of core legs to apply thereto a compressive force sufficient to establish without deformation of said laminations an equivalent frictional force as is applied to each of said first oppositely disposed pair of core legs.
2. The reactor core of claim 1 further comprising means for adjusting the position of said second oppositely disposed pair of core legs relative to said first oppositely disposed pair of core legs to thereby adjust the dimension of said diagonal air gaps.
3. The reactor core of claim 1 wherein said end plates have a plurality of discrete apertures therein aligned with discrete apertures in each of said first oppositely disposed pair of core legs adapted to receive therein a first set of compression bolts and a plurality of slotted apertures therein aligned with discrete apertures in each of said second oppositely disposed pair of core legs and adapted to receive therein a second set of compression bolts; said means include said second set of compression bolts and mating nuts therefor; and further including means for adjusting the position of said second oppositely disposed pair of core legs relative to said first oppositely disposed pair of core legs by means of the position of said second set of compressive bolts in said slotted apertures in said end plates and said spacer members thereby to adjust the dimension of said diagonal air gaps.
4. The reactor core of claim 1, 2 or 3 and further including two of said rectangular arrays of oppositely disposed first and second pairs of core legs in side-by-side relationship, said core legs being compressed together between end plates which extend over and compress therebetween the laminations of said two rectangular core arrays.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA276,326A CA1075784A (en) | 1977-04-07 | 1977-04-07 | Reactor core |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA276,326A CA1075784A (en) | 1977-04-07 | 1977-04-07 | Reactor core |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1075784A true CA1075784A (en) | 1980-04-15 |
Family
ID=4108405
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA276,326A Expired CA1075784A (en) | 1977-04-07 | 1977-04-07 | Reactor core |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1075784A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ITPN20120040A1 (en) * | 2012-07-05 | 2014-01-06 | Zucchiatti Bruno Elettromeccanica S Rl | ASSEMBLY OF THE CORE OF A TRANSFORMER AND ITS PROCEDURE |
-
1977
- 1977-04-07 CA CA276,326A patent/CA1075784A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ITPN20120040A1 (en) * | 2012-07-05 | 2014-01-06 | Zucchiatti Bruno Elettromeccanica S Rl | ASSEMBLY OF THE CORE OF A TRANSFORMER AND ITS PROCEDURE |
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