GB2194104A - Laminated stator core unit for dynamo-electric machine - Google Patents

Abstract

A stator core for an alternator comprises a stack of laminations 4 held within an outer tubular frame 1. Each lamination has an internal circular opening 5 formed with slots and teeth 6 and is basically square in shape with its corners rounded on a radius 8 to match the internal surface of the frame 1. Each lamination is angularly displaced in relation to the next adjacent lamination by 120 degrees so that the complete stack forms a substantially cylindrical body which may further be skewed. Each of the four corners of each lamination is formed to define a connecting notch 10, 10, 10 and 13, the notch 13 differing from the notches 10 in that it has a stepped recessed construction including steps 29 and 30. The aligned inner recesses of successive laminations are closed by a connecting bar 31 to which is welded a bar 33, in turn welded to the frame 1. Each corner also includes triangular openings 11, 14 which define axially extending air passages. <IMAGE>

Description

SPECIFICATION Stator core unit for dynamo-electric machine The present invention relates to a stator core structure for a dynamnoelectric machine, and particularly for an alternator supplying alternating current power to a load distribution system for one or more loads.

Dynamoelectric machines conventionally include an annular stator within which a rotating rotor is rotatably mounted. Engine driven alternators are used for generating alternating current powers in various applications are one example of such machines. Alternators are available for example for providing three phase alternating current at 240/480 volts. The alternator is generally a rotating field construction, with a three phase output winding wound within an annular stationary stator.

Conventionally, the stator is formed as a circular cylindrical member. The stator is fixedly and rigidly mounted with a tubular mounting frame. The heat generated by the relatively large currents in the windings require forced cooling of the stator to prevent damages to the winding and stator core structures. In open ventilated motors having forced cooling, suitable supporting spacers are circumferentially located about the stator core to space the frame outwardly and define cooling passageways between the outer tubular frame and the exterior surface of the stator core. An appropriate fan unit is coupled to the alternator shaft and is driven therewith to develop an appropriate forced air stream through the alternator and particularly over the stator core to continuously cool the alternator during operation thereof.

Totally enclosed alternators and other dynamoelectric machines are also produced without the internal passageways. In such machines, a finned frame or some other cooling means may be provided. q further highly significant consideration in the construction of dynamoelectric machines is the optimizing of the magnetic material in the core so as to produce an efficient magnetic circuit for the magnetic fields. Thus, cooling and mounting openings in the core tend to effect the path for the fields, and may generally in such a manner as to adversely effect the system.

Although such alternators have been constructed for many years and have produced commercially satisfactory operations, the construction of the core and the assembly to the various spacer and frame components into a fina! assembly is reasonably costly.

The stators are laminated structures formed of circular laminations. The laminations are stamped from a flat strip stock of appropriate magnetic material. There is also a significant material waste as the result of the circular configuration with the typical commercial production.

Various alternative constructions have been suggested wherein a substantially square lamination is used with the corners specially shaped for clamping of the stack of laminations together and for mounting of the core to a suitable frame structure when the square stator core is mounted in an annular encircling frame, cooling passageways are formed on the four sides of the core. Such a structure for example is shown in U.S. Patent no: 2,508,207.

A further modification to the use of a relatively square lamination is disclosed in U.S.

Patent no: 2,818,515. The lamination is formed with a special outer edge configuration defining outward projection from an annular continuous portion including the stator teeth and slots. The laminations are assembled into groups of laminations and the groups are rotated relative to each other to form a stator with circumferential projections and case within an encircling frame structure. The offsetting of the several groups and casting within the frame structure produces a series of tortuous paths about the projections and thus between the annular portion and the outer cast frame.

Although such structure has certain advantages from the standpoint of manufacture, the casting of a frame is not considered a preferred fabrication procedure in the grouped laminating form, the airflow path which is generally a tortuous path with sharp turns which may restrict rapid cooling of the alternator. Further, the flux pattern and movement within the core structure and particularly the outermost portions thereof is erratic and the extended portions would not appear to significantly contribute to the effective and efficient operation or magnetic functioning of the alternator. Thus, the flux paths within the stator core do not provide a smooth continuous magnetic path with minimum significant air gaps.The stator structure shown in U.S. patent 2,818,515 also includes the stator stacked between the pressure rings and having rods or irons anchored passing through the grooves formed by grouped laminations and forming an integrated part of the pressure rings and the frame to hold the stacked lamination together as shown in such patent.

There is a need for a laminated stator core structure which can be directly assembled with a tubular cylindrical frame, with an optimum flux distribution within the core and in selected designs with appropriate internal mounting and cooling passages.

According to the present invention a laminated stator core for a dynamo-electric machine comprises a plurality of like laminations, each lamination having a substantially square configuration and a central circular opening, the four corners of each lamination being rounded to have a radius corresponding to the inner diameter of a circular frame, the laminations being angularly displaced in relation to one another to off-set the corners and define a circular outer surface, at least one corner of each lamination being formed with a centrally located attachment notch and a plate member fixed within the notch and defining a continuous flat outer surface at a radius no greater than the outer radius of the corner structure, for securing the core to an outer frame mem ber.

With such a structure the stator core may be directly assembled within an appropriate and encircling tubular frame and the stator core may be constructed to produce a larger effective magnetic diameter, with a more uniform electrical flux distribution within the stator core. The stator may also be constructed to produce an efficient internal cooling of the stator core and interconnected and supported windings in an internally ventilated construc tion. The tubular frame is preferably formed from a plate member which is wrapped tightly about the core and with the opposed end edges of the frame plate welded to the core to secure the core within the frame.

The corner portions may be further provided with a plurality of circumferentially distributed openings where internal cooling passages are to be provided. The attachment notches and cooling openings when used are preferably formed in each corner to produce a plurality of circumferentially distributed aligned notches and openings. The notches and openings are restricted in the corner structure to the in creased outer radius portion to maintain a continuous annular core at least corresponding to the minimum thickness provided to the sides of the substantially square laminations.

The laminations are assembled in stacked rela tions to define an elongated stator core of the necessary axial length for the alternator and with a true constant diameter such that the wrapped frame engages the core through the interface therebetween. As mentioned, each lamination is angularly displaced relative to the adjacent laminations to define a continuous circular outer surface and with internal poles and slots of a particular design. In a preferred construction of three phase stator core, each lamination is rotated in the same direction of rotation for 120 degrees relative to the adja cent laminations.The notch and multiple open ings- in the corner portions are constructed and arranged such that the rotating lamina tions aligned the similar openings and define a plurality of essentially unobstructed cooling passages throughout each of the extended corner portions. Further, the corner portions are also provided with common edge notches - for welding of the laminations to each other, and where provided a connecting member, and thereby establishing an- integrated stator core.

In a skewed stator design, the stacked laminations are preferably constructed and rotated to establish skewed elongated notches and air flow openings for establishing improved stator functioning. At least one of the corners is form with a special attachment notch including outer offset portions. In the stacked laminated core, a rigid interconnecting bar unit is welded within the special attachment notch to define a frame connection surface. A frame connecting weld bar or plate is secured to an inner bar, with the bar in axial alignment with the axis of core. The assembled integrated laminated core is wrapped with an outer frame plate having a seam aligned with the weld bar or plate. The tightly wrapped frame is then welded in place to the weld bar to complete the interconnection of the frame and stator.

The punched laminations can be very accurately formed such that the integrated round core of the multiple rotated laminations has an outer diameter which is a true surface for interconnection of the frame. The edge corner welding notches contribute to easy fabrication of the stator assembly and the welded interconnection to the frames. Further, the square laminations with the use of the corner structures minimize material scrap while the punched slots provide an highly effective and large cooling surface. The multiple rotated laminations produces an increased effective magnetic diameter with significant magnetic symmetry, thereby contributing to the optimum electrical efficiency of the alternator.

More particularly in a preferred embodiment of the present invention, the corner structures of the laminations are specially formed with the securement notches and similar multiple openings formed to the opposite sides of each notch. Each lamination is rotated 120 degrees with respect to the adjacent laminations. All four corners are similarly formed with a central notch extending down through the continuous annular portion. The base of the notch is especially formed to receive a clamping rod which is welded to the aligned notched laminations in the stack to securely and firmly interconnect the several laminations along the corresponding peripheral edge at the twelve equicircumferentially notches on the outer periphery of the core. The number of grooves formed by aligned notches will vary with the degree of rotation and the described unit is for one practical design.

Openings in three of the corner structures are similarly formed and include a plurality of openings located to the opposite sides of the groove. In a preferred construction, three generally right triangular openings are formed to each side of the groove. The openings include a large opening immediately adjacent the notch and having the hypothenuse extending circumferentially and radially from the base of the notch to the outer edge of the rounded corner. Within the adjacent portion of the cor ner portion, a generally equi-sided triangle por tion includes two similar oppositely extending right triangle openings having substantially equal sides and being substantially smaller than the first opening.

The multiple triangular openings produce a high strength stator core. Although the use of a plurality of such openings somewhat decreases the size of the air passages, an increased cooling surface is created and essentially similar cooling is obtained while maintaining the high strength.

The laminations formed for skewed slots also creates skewed notches and air passageways through the alternator core.

The one or fourth corner structure is formed with a specially formed notch having an inner central portion for receiving a welded connecting rod. The outer portion of the connecting corner however is not provided with the first air openings. Rather, the outer corner portion is maintained continuous with a stepped notched or recessed outer construction. The stepped recessed portion defines an inner recess which is closed by a support plate. A frame welding bar is welded within the outer stepped recess and particularly to the closed recess. The frame welding bar is located in parallel alignment with the axis of the core and defines an aligned surface for welding of the frame seam to the core.

The ventilated stator structure provides a highly efficient and economical method of forming and fabricating the stator for a dynamoelectric machine and particularly a power alternator or the like with improved magnetic filed flux distribution. The rotation of the lamination causes the "effective" magnetic diameter to be larger than the distance across the flat side edges or walls of the core and also maintains magnetic symmetry about the stator. The material of the square laminations are effectively totally used except for a small portion of the lamination which is removed to define the circular outer true diameter, and the use of the corner pprtion effectively enlarges the magnetic diameter.In an internally ventilate machine, the multiple air vent slots produces a highly effective and extended cooling surface area, without sacrificing the magnetic characteristics of the stator core and without the necessity for multiple part component assembly such as heretofore widely used in the construction of alternators. The use of true core outer diameter permits easy and convenient fabrication and assembly of the outer frame and structure and its interconnection to its stator core.

The total construction therefore significantly contributes to the commercial implementation with present day technology.

The invention will now be described in more detail with reference to the accompanying drawings, in which: Fig. 1 is a plan view of an alternator stator unit with parts broken away and sectioned to illustrate inner detail of the construction; Fig. 2 is an end elevational view of the alternator stator core taken generally on line 2-2 of Fig.1; Fig. 3 is an enlarged fragmentary view of the stator core illustrating the attachment structure for attachment to the frame; Fig. 4 is a view taken generally on line 4-4 of Fig.2; Fig. 5 is a elevational view with parts broken away to further show the frame and core attachment; Fig. 6 is a multiple view illustrating steps in the assembly of the alternator stator core shown in Figs. 1-5; and Fig. 7 is an enlarged fragmentary view of the core further illustrating the forming of the stator core.

Referring to the drawing and particularly to Fig. 1, an alternator unit is illustrated including an outer tubular frame 1 within which an an nular stator core 2 is rigidly affixed. A stator winding 3 is wound in the stator core, and a rotating magnetic field rotor, not shown, is rotatably mounted within the stator core to generate a magnetic field cutting the stator winding in accordance with conventional practice to generate an alternating output. The illustrated alternator is adapted to generate operating power for driving of multiple consuming loads and the electrical efficiency of the stator construction is of substantial significance. The operation of the alternator also generates significant heat within the winding.

The alternator is provided with a forced cooling means such as a fan coupled to the rotor.

The core 2 is specially formed with air passages 3a in the outer portion of the core adjacent the stator frame 1.

The present invention is particularly directed to the construction of the stator core 2 and its interconnection to the encircling outer metal frame 1 and a preferred embodiment and method of fabrication is shown and described.

Referring to the Figs. 2-4, the laminated stator core 2 is formed from a plurality of like laminations 4, particularly shown in a preferred construction in Fig. 6. The square lamination 4 has an internal circular opening 5 with the stator slots and teeth 6 formed on the inner surface portion. The width of the lamination on the diametrically opposite flat sides 7 are equal and correspond to a minimum core thickness desired for optimum alternator design. The lamination 4 is basically formed as a square flatted member which is stamped from a suitable metal stock. The four corners of the lamination are removed on a radius 8 corresponding to the final diameter of the core 2.

The round edges of the corners are formed with a substantial circumferential length, and typically about 30 degrees. The corner portions of the square lamination 4 define radial outward extensions of the continuous annular portion including the slot and teeth 6.

Generally, each of the four corners is formed to define a lamination connecting notch and a plurality of air passages or openings. Three of the corners are formed with similar construction including a centrally located notch 10 and plurality of similar air passage openings 11 located to the opposite side of the notch 10. The fourth corner 12 is formed with a special notch 13 and lesser but similar openings 14 to the opposite side of its notch 13.

Referring to one of the three similar corners 9 which are identically formed, a description thereof is given in detail, with corresponding elements of the other two corners identified by the corresponding prime and double primed numbers. (See Fig.7) The corner structure 9 is formed with the cylindrical outer radius and with the notch 10 located centrally thereof.

The notch 10 projects inwardly symmetrically about a radius line. The notch 10 includes tapered sidewalls 15 defining a large entrance opening which decreases inwardly of the notch to a notch base 16. The base 16 is concave and connected to the inclined sidewails 15 by small circular connections 17. The inner end of the notch 10 defines a connecting recess for receiving of an interconnecting weld for directly welding of adjacent lamination. Alternatively an interconnecting round bar 18 is located in selected notches and welded to clamping end rings to securely clamp the lamination into a rigid core structure. The latter structure is generally used in larger sized cores.

The base of the notch is located or spaced outwardly a sufficient distance from the inner rotor opening 5 to maintain a continuous annular portion of a length somewhat greater than the width of the lamination at the sidewall or edges 7 of the laminations.

The plurality of openings 11 are located in symmetrical fashion to the opposite sides of the notch 10 on a radius line passing through the base 16 such that the basic core stock is maintained at a minimal dimension and the corners form an enlarged extension of the magnetic material.

In the illustrated embodiment of the invention, right triangular openings 11 are similarly formed to the opposite side of the connecting notch 10. The openings 11 include a first relatively large opening having the right angle legs 20 and 21 extending respectively parallel to the adjacent side edge of the notch 10 and a radially outermost edge 21 extending generally parallel to the outer edge of the circular corner 8. The hypotenuse edge 22 of the triangular opening 11 extends circumferentially and radially outwardly from the leg 20 adjacent notch 10. The edge 22 is also specially located with respect to the notch 10 and particularly to form a tangent to the circle generated within the base. This sets a reference edge such that aligned and rotated laminations maintain unobstructed notches and openings throughout the axial length of the stack of laminations.The opening contracts from adjacent the notch outwardly toward the periphery of the core. The small end of this opening 11 is located to define a generally triangular portion with the adjacent straight side edge 7 of the lamination. Within such triangular portion, a pair of oppositely extended small right triangular openings 11 are formed. The one opening is located with its hypotenuse 23 spaced inwardly and partially overlapping with the hypotenuse edge 22 of the first opening. The first smaller opening 11 expands laterally outwardly towards the side wall with right angle legs 24 extending respectively circumferentially and radially. The second opening 11 is in a reversed orientation and generally corresponds in size to the first small opening.The base leg 25 is spaced from the base leg 24 of the first small opening and the hypotenuse 26 is generally parallel to the side edge 7 of the lamination 4.

Similar openings 11 are provided to the opposite side of the notch 10 with corresponding construction and orientation, as shown in Fig. 7.

As previously noted, the other two adjacent corners 9 are similarly constructed.

The fourth corner 12 has the unique notch 13 which is specially constructed for interconnecting of the stator core 12 to the encircling metal frame 1.

The notch 13 has an inner base portion 28 (Fig.3) essentially corresponding to the inner base portion of the notches 10 in the other three corners. The outer portion of the notched 13 however includes a stepped recess construction having stepped sidewalls including first and second steps 29 and 30. The first step 29 adjacent the base portion defines an opening and recess somewhat larger than the opening to the inner tapered base portion 28.

The second outer step 30 forms a second larger recess adjacent the periphery of core 2.

As shown in Figs. 3 and 4, the inner recess is closed by a connecting bar or plate 31 which is located within the steps 29 and closes the base portion 28. The plate 31 is located coplanar with the base of the enlarged outer steps 30. This provides an enlarged continuous wall for the outer recess within the outer circumference of the lamination and the core 2. The total width of the enlarged recess is selected such that a frame weld bar 33 extending precisely parallel to the axis of the core 2 is located within the enlarged skewed notch. Thus, the skewed formation of the openings and the connecting notches on the outer periphery of the core 2 would normally prevent the axial alignment of the weld bar in the notched structure.The enlarged notched recess structure establishes the necessary width to accommodate the axial orientation within the skewed notch. (Fig.4) As the result of the enlargement of the notched structure, the large openings 11 adjacent to the notch as provided in corners 9 are eliminated from corner 12 of the lamination 11. Small openings 14 are similarly located and formed in the corner structure.

The orientation and construction of the openings are such that the rotation of adjacent lamination through 120 degrees aligns the several openings on the correspondingly shaped corners. The unique fourth corner 12 develops three aligned enlarged notches 13 extending longitudinally throughout the length of the assembled stacked laminations. The frame mounting notches 13 will be spaced from each other by 120 degrees. The outer interconnecting notches 10 and 13 are equicircumferentially spaced about the core 2. The stator core assembly otherwise presents a continuous true circular outer surface. The aligned openings 11 in every third lamination establishes a series of individual air passageways through which a high velocity cooling air passes for efficient cooling of the core and stator winding.

The intermediate grooves define 12 grooves for welding or interconnecting of the- laminations to each other to securely interconnect the laminations into a single integrated structure. The special frame notches 13 have the inner portion formed for receiving of interconnecting welds and/or welded bars deposited therein and welded to the laminations.

The three special notches are closed with the plate 31 located within the smaller inner stepped recess 29. The plate 31 is welded in place by welds 34 and 35 which extend inwardly from the opposite edges of the lamination core 2. Weld 35 extends from the one face of core inwardly only to the intersection with the frame bar. Weld 35 is formed from the opposite face of core 2 to its location or intersection with the frame bar 33. The axial frame bar is located in appropriate axial location and the opposite edges welded to the plate 31 including a first weld 36 from the weld 34 of the first bar welded to the outer end of the bar, and'a second weld 37 from weld 35 to the end-of bar 33.

The width of the bar is selected for proper welding of the frame to the bar. The length of the frame bar 33 is somewhat less than the length of the core 2 for subsequent fabrication to the frame. The frame bar 33 must be flush with or below the outermost diameter of the finalized core 2. This is necessary to insure that the frame 1 tightly wraps about and engages the true cylindrical surface of the stator core 2 in the wrapped, aligned and welded in place position.

In summary, the stator core 2 is formed as described above with the rotated laminations 4 welded along the base of the notches 10 and 13 and notches 13 closed by plate 31 and bar 33. A frame plate 1 is tightly wrapped about the core 2 using appropriate machinery and with the opposed and generally abutting edges of the frame plate 1 aligned with the welded outer frame bar 33. The frame is welded to the frame bar as by a longitudinal weld 38. A pair of extended bars 39 are located on the frame in alignment with the welded frame bar 33 and extend outwardly as extensions thereof. The frame seam 38 is welded to the bar 33 and to bars 39 to weld the frame 1 to the core and close the frame seam.

The present invention provides an improved magnetic core as the result of the "flatted laminations" having integral corners located such that with the appropriate rotation of each lamination to define a true outer core diameter for the frame, and the attachment notches, and as well as the ventilating passages when incorporated into the design which are integrally formed within the lamination produce a maximum effective magnetic diameter with symmetrical magnetic distribution, and highly effective cooling passageway. The rotation of each of the laminations is highly desirable to maintain the proper optimum magnetic symmetry within the core structure and thereby maintaining the most effective and efficient functional operation of the stator core assembly. There is a minimum amount of scrap because of the extended corner structure to obtain the larger magnetic diameter as well as the integral air passageways. The proper assembly of the laminations to a stacked assembly to provide a true cylindrical surface is readily provided and forming of the laminations as well as the minimum fabrication required to interconnect the core bars and the frame are significant in permitting commercial usage of the invention.

Claims (25)

1. A laminated stator core for a dynamoelectric machine comprising a plurality of like laminations, each lamination having a substantially square configuration and a central circular opening, the four corners of each lamination being rounded to have a radius corresponding to the inner diameter of a circular frame, the laminations being angularly displaced in relation to one another to off-set the corners and define a circular outer surface, at least one corner of each lamination being formed with a centrally located attachment notch and a plate member fixed within the notch and defining a continuous flat outer surface at a radius no greater than the outer radius of the corner structure, for securing the core to an outer frame member.

2. A stator core according to claim 1 having a plurality of corresponding openings within the corner portion of the lamination opposite to the notch.

3. A stator core according to claim 1 or claim 2 wherein each lamination is displaced the same number of degrees relative to the adjacent laminations.

4. A stator core according to claim 3 wherein each lamination is displaced in the same direction by 120 degrees with respect to the adjacent lamination, and defining equicircumferentially spaced skewed connecting notches, the attachment notch including outer stepped side walls defining a small inner recess and a large outer recess with an inner plate member secured within the inner recess and closing the base of the outer recess, the plate member being welded within the outer recess axially aligned with the axis of the core.

5. A core according to any one of claims 1 to 4 wherein a frame tightly encircles the stacked laminations and has a single seam aligned with and welded to the plate member.

6. A laminated core according to any one of the preceding claims wherein three of the four corners are correspondingly formed and each includes an attachment notch and openings to each side of the notch including a first triangular shaped right triangular opening having sides extending generally parallel to the notch and to the outer circumferences of said corner and having a hypotenuse extending circumferentially and radially outwardly between the opposite outer edges of the side legs, first and second triangular smaller openings located with one of the openings partially having a hypotenuse adjacent and partially overlapping the hypotenuse of the first triangular opening and having a base portion extended and located outwardly and generally aligned with the adjacent edge of the circular edge of the corner, the second smaller opening generally corresponding to the first smaller opening and located as essentially mirror image of the first smaller opening within the hypotenuse generally parallel to the side edge of the lamination and the fourth corner of each lamination includes the attachment notch with the stepped side walls and having openings corresponding to the first and second triangular smaller openings.

7. A core according to any one of the preceding claims, wherein each of the rounded edges of the-corners of the laminations has a length of about 30 degrees.

8. A laminated stator core for an A.C. alternator, comprising a plurality of like laminations, each having a substantially square configuration and a circular central opening, the four corners of each lamination being rounded to have a radius corresponding to the inner diameter of a circular frame, the laminations being angularly dispiaced in relation to one another to off-set the corners and define a circular outer surface and to define a skewed stator core, the corners of each lamination being correspondingly formed with a centrally located attachment notch, and a plurality of corresponding openings within the corner portion of the lamination to the opposite side of the notch, the central notch of at least one of the four corners of the lamination including stepped side walls defining a large outer recess and an inner recess, a plate member fixedly secured within the inner recess and defining a continuous flat surface with the stepped wall of the outer recess, and an axially aligned second plate member fixed in the outer recess defining an outer surface at a radius no greater than the outer radius of the corner structure.

9. A stator core according to claim 8 wherein the first plate member is welded to the laminations and the second plate member welded to the first plate.

10. A stator core according to claim 8 or claim 9 wherein each lamination is displaced relative to the adjacent lamination.

11. A stator core according to claim 10 wherein each lamination is displaced in the same direction by 120 degrees with respect to the adjacent lamination and defines equicircumferentially spaced skewed connecting notches.

12. A core according to any one of claims 8 to 11 wherein a frame tightly encircles the stacked laminations and has a single seam aligned with the second plate, and means affixing the seam to the second plate member.

13. A core according to any one of claims 8 to 12 wherein three of the four corners of each lamination are correspondingly formed and each includes openings to each side of the notch including a first triangular shaped right triangular opening having sides extending generally parallel to the notch and to the outer circumference of the corner and having a hypotenuse extending circumferentially and radially outwardly between the opposite outer edges of the side legs, first and second trian gular smaller openings located with one of the openings partially having a hypotenuse adjacent and partially overlapping the hypotenuse of the first triangular opening and having a base portion extended and located outwardly and generally aligned with the adjacent edge of the circular edge of the corner, the second smaller opening generally corresponding to the first smaller opening and located as essentially mirror image of the first smaller opening within the hypotenuse generally parallel to the side edge of the lamination.

14. A core according to claim 13 wherein the fourth corner of each lamination includes openings corresponding to the first and second triangular smaller openings.

15. A core according to any one of claims 8 to 14 wherein each of the rounded edges of the corners of the laminations has a length of about 30 degrees.

16. A stator assembly comprising a plurality of essentially identical laminations having a central rotor opening, each lamination having a generally square configuration with a diammetrical length from side-to-side defining a minimum effective magnetic core diameter, the laminations being stacked to form an annular core, each of the four corners of each lamination having a circular surface of a radius corresponding to the radius of the inner diameter of a mounting frame, the corners having interconnecting notches for inter-connecting the laminations and selected notches forming attachment notches having a frame member closing the corresponding notch and defining a member extending parallel to the axis of the core, the laminations being each displaced a corresponding number of degrees in the same direction in relation to the adjacent laminations to distribute the corners and define an essentially continuous circular outer core surface, and a tubular mounting frame enclosing the core and secured to the frame member.

17. A stator assembly according to claim 16 wherein the notches are skewed, and the selected corner notches have an outer closed recess having a base wall of a width defining a clear axial length, the frame member being welded to the base of the recess.

18. A stator assenbly according to claim 16 or claim 17 wherein each attachment notch projects inwardly centrally of the lamination corner with the innermost edge of the notch generally spaced to maintain a minimal magnetic path between the winding slots and the notch at least as great as the distance between the winding notches and the aligned side notches of the rectangular lamination, at least one opening located to one side of the notch and a second mirror image opening located to the opposite side of the notch, the openings being formed with an elongated linear innermost edge, angularly oriented at an angle related to the angle of displacement and extending on a tangent to the centre of the base of the notch whereby the angular orientation of the adjacent laminations results in the alignment of the openings in spaced laminations and the displacement of the adjacent laminations aligns the side edges with the base of the notches thereby maintaining complete axial exposure of the notches to define corresponding edge grooves.

19. A stator assembly according to claim 18 having an attachment notch in each of the corners whereby a plurality of circumferentially distributed attachment notches are located about the stator core.

20. A stator assembly according to claim 18 or claim 19 wherein the attachment notch includes inclined side walls and an inner base wall connected by a round corner and the displaced laminations adjacent the notch have their side edges aligned with the round corners of the notch.

21. A fixed stationary core unit adapted to be mounted within a cylindrical frame and having a plurality of inner winding slots circumferentially distributed within the inner openings of the core, comprising a plurality of core laminations, each comprising a substantially generally square outer perimeter having a width less than the diameter of the core and a corner diagonal length in excess of the core diameter, the corners of the lamination being removed on a radius corresponding to the diameter of the radius of the core, the length of the radius corners being substantial, the laminations being stacked with the inner rotor opening having the winding slots in each lamination defining predetermined axially extended winding slots within the stack of laminations, the stack of laminations having immediately adjacent laminations angularly displaced whereby an essentially continuous circular outer peripheral surface is generated by the stack of laminations, and means to secure the laminations in the displaced orientation to form a rigid core structure.

22. A core unit according to claim 21 wherein at least one corner of each lamination includes a securement notch, the displacement of the laminations aligning a plurality of the notches to define an axially extending groove on the outer surface of the laminations, and means disposed in the groove, connected to the laminations and to the adjacent interposed laminations to securely lock the stack of laminations in place.

23. A core unit according to claim 22 wherein the notches have a depth whereby the adjacent rotated notches have a side aligned with the base of the notch to define a substantially continuous surface throughout the base of the aligned notches, and at least one of the grooves having a weld extending through the length of the groove.

24. A core unit according to claim 23 wherein each corner of the laminations includes a notch, each of the laminations being displaced by essentially the same number of degrees and being rotated at least 30 degrees, whereby every lamination by the number equal to the angular rotation divided into 360" has the four corners aligned, and thereby providing aligned corners for each corresponding angular rotation, a plurality of corners of each lamination being provided with edged securement notches and thereby defining a plurality of circumferentially distributed grooves on the periphery of the stack of lamination, means disposed within the grooves for interconnecting of the laminations into a rigid stable stack of laminations having a true cylindri cal outer surface.

25. A stator lamination unit adapted to be stacked with similar laminations to form an annular stator core having an axis, comprising a flat lamination of a substantially square configuration having a minimum effective magnetic diameter defined by the diammetrical distance from one edge of the lamination to the opposite edge of the lamination, said lamination being adapted to be mounted within a circular tubular frame having a diameter of less than the diametrical corner-to-corner distance of the lamination, the four corners of said lamination being removed and formed with a radius corresponding to said core diameter, three of the corners of said lamination being correspondingly formed and each having a centrally located connecting notch and a plurality of corresponding openings generally within the corner portion of the lamination to the opposite side of said notch, said openings to each side of said notch including a first right triangular opening having sides extending generally paral lel to said notch and to the outer circumference of said corner and having a hypotenuse extending circumferentially and radially outwardly between the opposite outer edges of said opening sides, first and second triangular smaller openings located with a first of said smaller openings partially having a hypotenuse adjacent and partially overlapping the hypotenuse of said first triangular opening and having a base portion extended and located outwardly and generally aligned with the adjacent edge of the circular edge of the corner, said second smaller opening generally corresponding to said first smaller opening and located as essentially a mirror image of said first smaller opening with a hypotenuse generally parallel to the side edge of the lamination, the fourth corner of said lamination having a central frame notch with an inner portion essentially corresponding to an inner portion of the central notch of the outer corners and having the inner most portion thereof generally located radially in accordance with the outer notches, the outer portion of said frame notch having stepped outer sidewalls defining an inner recess adjacent said inner portion and an outer recess, said stepped sidewalls of said inner recess being adapted to receive a plate member- for closing the notch and defining a continuous surface across the notch, said outer recess adapted to receive a frame bar defining an outer surface having an outer radius no greater than the outer radius of the corner structure, said frame bar being located within said outer recess and located axially of the core.