US 3130335 A
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Description (OCR text may contain errors)
A nl 21, 1964 1.. J. REJDA 3,130,335
DYNAMIC-ELECTRIC MACHINE Filed April 17, 1961 Fl(5.l H02 ll l2 ll l2 ll I2 20 I2 H 12 II II l2 l2 ll 30 20 I2 ll l2 II INVENTOR LADISLAV J. REJDA BY Jim, 131m, iwwmmm'e ATTORNEYS United States Patent 3,l3,335 DYNAMQ -ELECTREQ MACH-ENE Ladislav J. Rejda, El Monte, (Iaiifi, assignor to The Epoxyiite Corporation, El Monte, Califi, a corporation of California Filed Apr. 17, 1961, Ser. No. 103,449
9 Claims. (Cl. 310215) This invention relates to dynamo-electric machines and more particularly to slot liners for such machines.
Certain dynamo-electric machines such as motors and generators utilize magnetic cores in which elongated slots are disposed to receive electrical windings. A serious problem which confronts the art is the prevention of moisture from intruding into the windings within the slots to cause deterioration and even short circuiting. In an attempt to exclude such moisture, it has been a practice for many years to employ moisture resistant liners in the slots surrounding the windings. Slot liners have been constructed of such materials as treated fabric or paper, rubber, refractory materials, glass and various combinations of such materials. Liners formed from these materials have been attended by practical disadvantages. Where the liners are sutficiently flexible and workable to facilitate manufacture and provide a compact product, they necessarily have been so thin as to limit their moisture resistance and their useful life. Still further, these materials do not adequately dissipate heat generated by the operation of the dynamo-electric device.
In recent years, thin nonmagnetic metal foil has been employed as slot liner material. The use of metal foil can be a substantial improvement over the materials mentioned above because metal even in the form of thin flexible foil is highly impervious to moisture. Moreover, the thin foil is very workable and easily conforms to desired configurations. The metallic foil slot liners, however, must be carefully insulated from the windings by g a suitable dielectric material. Moreover, a fabrication problem is presented because the slot liner must be initially placed in the slot and the windings emplaced within the liner with insulating material between the metallic liner and the windings. Heretofore, available devices have provided at least one opening extending axially the entire length of the metallic slot liner through which opening the windings may be passed during assembly. In prior art devices, however, such openings, while permitting fabrication of the windings, have provided in the finished device access for the intrusion of moisture into the windings. No satisfactory liner construction has heretofore been available which permits closure of the opening "ice having a slotted core of magnetic material with windings in the slots; a tube of nonmagnetic metallic foil disposed coaxially Within each winding slot, surrounding the electrical windings which are disposed in the slot and separating the windings from the core iron defining the slot; and a second tube of insulating material disposed in each slot wholly within the metallic foil tube and surrounding the windings to electrically insulate the windings from the foil.
Further objects, features, and attending advantages of the invention will become apparent by reference to the following detailed description and accompanying drawings, in which:
FIGURE 1 is a partial view in front elevation of a segment of a dynamo-electric machine core, showing a first step in preparation of one slot liner of this invention, and prior to insertion of the windings in the slots;
FIGURE 2 is similar to FIGURE 1, and illustrates a further stage in the preparation of the slot liner;
FIGURE 3 is a detail of one of the slots illustrated in FIGURES 1 and 2 with the windings inserted in the slot;
while adequately insulating from the windings the metallic edges which define the opening. I
To overcome the disadvantages of the prior art it is a primary object of this invention to provide an improved nonmagnetic metallic foil slot liner for the winding slots of dynamo-electric machines which liner is constructed to provide an axially extending opening for the insertion of the windings through the liner during fabrication but which forms a completely closed tube in the finished device to minimize intrusion of moisture into the windings and also provides complete insulation between the foil and the windings.
Another object of the invention is to provide such an improved insulated nonmagnetic metal foil slot liner which is inexpensive and easily installed.
Still another object of this invention is to provide an improved process for fabricating a slotted dynamo-electric machine core with the windings completely enclosed in the slots by nonmagnetic metal foil slot liners, and insulated from such slot liners.
Briefly, and in accordance with one aspect of this invention, there is provided a dynamo-electric machine FIGURE 4 is a view identical to that of FIGURE 3 with the windings and slot liner of this invention, in section, as completed;
FIGURE 5 is a perspective view of the completed assembly illustrated in FIGURE 4; and
FIGURE 6 is a fragmentary sectional view of one of the slots showing a modified slot liner according to the invention.
With reference to FIGURE 1, there is shown generally indicated at 10 the core of a dynamo-electric machine, usually comprised of a stack of ferro-magnetic laminations. The core of which FIGURE 1 represents 21 segment is annular in. configuration, having a plurality of winding slots 11 cut radially outward from the inner periphery of the annulus and extending the axial length of the core. As is well known in the art, the slots 11 receive the conductive windings of the core It).
Slots 11 may be of any desired form, but are illustrated here as following the common practice to provide a narrow neck portion 12 to facilitate closing off the slot to retain the windings therein.
The method by which the liner for a given slot 11 is prepared will now be described.
A sheet of nonmagnetic metallic foil 20, shown in cross-section in FIGURES 1 through 4, is placed in the core slot 11 to extend at least the axial length of the slot. In placing the metallic foil 20 into the slot, it is loosely folded or curled and inserted through neck portion 12 until it rests against the bottom of the slot 11, as illustrated in FIGURE 1.
With reference to FIGURE 2, a thin sheet 30 of suitable insulating dielectric material is then loosely folded or curled and, like foil 20, is inserted through neck portion 12 of slot 11 until it comes to rest against and conforming generally with metallic foil 20. The sheet 30 lies loosely within and unbonded to the foil sheet 20. Dielectric material 3% should be at least as long as the sheet of metallic foil 20, but as described more fully below, is preferably longer in axial length than metallic foil 20.
With reference now to FIGURE 3, conductive windings 40 may be laid through neck portion 12 so as to lie within the slot 11 and within the foil and insulating sheets. Where desired for the particular type of winding, a center stick 50 may be laid within the slot midway between the first and second halves of the winding body.
Thus, it will be seen that when assembled within slot 11, the conductive winding 40 is separated from the slot by the metallic foil 20 and the sheet of dielectric material 30.
With the reference now to FIGURE 3, foil 20 has edges 21 and 22 protruding from the neck portion 12 of slot 11. Similarly, the sheet of dielectric material 36 has opposite edges 31 and 32 protruding from neck portion 12. With reference to FlGURES 3 and 4, it will be seen that completion of the slot liner is effected by first folding over the opposite edges 31 and 32 of the sheet of dielectric material 3d, thereby forming an overlapping seam extending the length of the tubular liner; similarly, opposite edges 21 and 22 of the sheet of metallic foil 20 are then folded over in overlapping relation to form a like seam. The overlapping ends of the foil are bonded to each other by strongly adherent insulating adhesive such as an epoxy resin to form a moisture proof joint. If desired the overlapping ends of the insulating liner may also be bonded together by an insulating adhesive.
As seen with reference to FIGURES 4 and 5, the sheet of dielectric material 39 forms a closed tube, open at the ends, extending a distance greater than the axial length of the slot, and surrounding the windings 4G to insulate them from the sheet of metallic foil 29. Similarly, the sheet of metallic foil 2%) forms a closed tube, open at the ends, and extending a distance greater than the axial length of the core slot 11. The closed, moisture impermeable tube forrned by the continuous sheet of metallic foil 20 forms a protective barrier for the windings against any moisture tending to travel into the slot 11. It is important to close the inner tube of insulating material first by forming its overlapping seam and then to similarly close the outer metal tube. In this manner, the inner tube completely insulates the raw opposite edges of the metal tube, which define the opening for emplacement of the windings, from the windings to preclude short circuiting between the windings and the metal tube.
With reference now to FIGURE 5, the sheet of metallic foil 2t) is shown extending slightly beyond each axial end of slot 11 to insure against axial migration of moisture reaching the windings. The tube formed by the sheet of dielectric material 30 extends beyond each axial end of the metallic foil 2%. The purpose of the additional length of dielectric material is to prevent the occurrence of an electrical short circuit between the windings 4t and metallic foil 20. With the overlapping seam and by virtue of the fact that the sheet of insulation, along its length, completely surrounds the electrical conductors, it provides full insulation of the conductors from the metallic foil.
Illustrated in FIGURE 6 is an alternative construction according to the invention which is identical in its structure and method of assembly to that previously described except as detailed hereinafter. In the alternative embodiment, a sheet of nonmagnetic metallic foil Ztla is placed in the core slot 11 to extend at least the axial length of the slot and preferably longer. A thin sheet Z-ltla of insulating dielectric material is inserted through the neck portion of the slot 11 until it rests against and conforms generally to the metallic foil 20a. The sheet 30a lies loosely within and unbonded to the sheet Ztla. The insulating material preferably is longer in axial length than the foil material as previously described. The sheets Ztla and 30a are identical to the sheets 2t) and 30 except that the former have a shorter circumference. The circumference is such that when the sheets 29a and 30a are formed into tube shape in the slot, they leave a gap extending axially along the upper periphery of the tube instead of having overlapping ends such as the sheets 249 and 3t). After the sheets Ztla and 30a are in place conductive windings 40 are emplaced through the gap between the ends of the sheets in the same manner as previously described. Similarly a center stick t may be employed if desired.
The insulating material Eltla is first closed to form a complete tube by placing over the gap at the upper ends of the sheets a curved strip 61 which is wider than the gap to form an overlap with the ends of each of the sheets and as long as the slot liner tube. The strip 61 may be of fairly rigid paper or other insulating material. If desired the strip 61 may be bonded to the ends of sheet 3% by suitable insulating adhesive material.
Subsequently the gap at the top of the foil sheet Ztla is closed by a strip of foil 62 which may be of the same material as the foil in the sheet Zita. The strip s2 desirably is the same length as the tube formed by the sheet Zita and is substantially wider than the gap between the ends of the sheet Zita to form an overlapping seam with each of such ends. The strip 62 is bonded to the ends of the sheet Ztla by a strongly adherent insulating adhesive such as an epoxy resin to form a moisture-proof joint.
After completion of the winding and liner assembly in either of the described embodiments, some suitable means is used to close slot Ill such as the slot wedge 60 which may be inserted as previously described.
If desired, in either of the described embodiments, the windings may be encapsulated in an insulating material within the slot liner assembly. The encapsulating medium may be introduced through the slot liner tubes through one end thereof or through a suitable temporary opening in the side of the tubes which opening is later closed and sealed. Sufficient encapsulating medium may be introduced into the tubes to fill the interstices of the windings and the spaces between the windings and the slot liner. Any suitable insulating encapsulating medium may be employed as described in my co-pending application Serial No. 86,254 filed lanuary 31, 1961, entitled Encapsulation of Electrical Power Component. A preferred encapsulating medium is epoxy resin as set forth in the said co-pending application. If desired, the epoxy resin encapsulating medium may be used to seal the overlapping seams of the paper and foil slot liners of either embodiment. Alternatively the seams may be presealed and the encapsulating medium subsequently introduced.
Preferably, the axial ends of the slot liner tubes are secured and covered by an insulating material such as epoxy resin. The sealing material may be sprayed or otherwise applied on the ends of the tubes. Such end closure desirably is accomplished whether or not the windings within the slot liner assembly are encapsulated.
Accordingly, the slot liner tube is completely closed so as to be moisture-proof and gas-proof.
The dielectric material for the sheets St) or 39a may be any suitable insulating material including without limitation paper. Mylar, varnished fabric, glass, mica, polyester resin, or combinations of any of the foregoing. T1 e foil of sheets 20 or Ztla may be formed of any suitable nonmagnetic metal such as stainless steel or aluminum. Stainless steel is preferred because of its greater strength. The foil sheets should be continuous and unbroken to insure moisture impermeability. Epoxy resins which may be employed are set forth in application Serial No. 675,- 280 filed July 31, 1957, entitled Epoxy Carboxylic Acid Dianhyclride Compositions.
In view of the foregoing disclosure, it will be seen that the slot liner of this invention is inexpensive, simple and reliable. The metallic foil is ideal for its strength, flexibility and moisture impermeability. Since it completely surrounds the winding, it is difficult or impossible for moisture entering the slot from the lamination at any point to reach the windings without first traveling at least to the end of the metallic foil in either direction. It is equally usable with or without additional treatment of the unit, such as encapsulating the winding in an insulating material; it is easily adaptable to manufacturing processes, either manual or mechanical and requires no extensive preliminary preparation or additional parts other than those commonly available.
While the invention has been illustrated and described with respect to a specific embodiment, it will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the invention as defined solely by the claims.
1. An insulating liner for an electric motor core winding slot, said liner comprising a nonmagnetic metallic foil tube disposed within and coaxial with said slot, said tube being formed by a sheet of foil with the longitudinal edges engaging each other to form said tube, bonding means sealing together the entire length of said engaging edges to provide a substantially moisture-proof wall which completely surrounds the motor winding in the slot, and means between said tube and said winding electrically insulating said windings from said metallic foil.
2. An insulating liner for an electric motor core winding slot, said liner comprising a substantially moistureproof tube coaxially within said slot and extending at least the length of said slot and surrounding the winding conductors in the slot, said tube being formed by a sheet of nonmagnetic metallic foil having opposite edges thereof overlapped, bonding means forming said overlapped edges into a substantially moisture-proof searn generally parallel to the-slot axis, and means between said tube and said winding electrically insulating said winding conductors from said metallic foil.
3. An insulating liner for an electric motor core winding slot, said liner comprising a substantially moisture-proof tube coaxially within said slot and extending at least the length of said slot and surrounding the winding conductors in the slot, said tube being formed by a sheet of nonmagnetic metallic foil having opposite edges thereof spaced apart and covered by a strip of nonmagnetic metallic foil overlapping and bonded to said edges to form a substantially moisture-proof seam generally parallel to the slot axis, and means between said tube and said winding electrically insulating said winding conductors from said metallic foil.
4. An insulating liner for an electric motor core winding slot, said liner comprising a first substantially moistureproof tube of nonmagnetic metallic foil coaxially within said slot and extending at least the length of said slot, a second tube of insulating material disposed within said first tube and surrounding the winding conductors within said slot, each of said tubes comprising a bent sheet having overlapping opposite edges bonded to each other to form a substantially moisture-proof seam generally parallel to the tube axis, said second tube having both of its overlapping edges inside the inner wall of said first tube.
5. The structure as recited in claim 4 wherein said second tube extends beyond said first tube at each axial end thereof.
6. The structure as recited in claim 4 wherein said second tube is paper.
7. An insulating liner for an electric motor core winding slot, said liner comprising a first substantially moistureproof tube of nonmagnetic metallic foil coaxially within said slot and extending at least the length of said slot, at second tube of insulating material disposed within said first tube and surrounding the winding conductors within said slot, each of said tubes comprising a bent sheet having spaced opposite edges covered by a strip overlapping and bonded to said edges to form a seam generally parallel to the tube axis, said second tube having both of its overlapping edges inside the inner wall of said first tube.
8. A dynamo-electric device comprising a core of magnetic material having a plurality of slots, a current carrying winding in each of said slots, a tubular liner coaxially within each of said slots extending at least the length of the slot and surrounding the winding in the slot, said liner comprising a substantially moisture impermeable outer sheet of nonmagnetic metallic foil and an inner sheet of insulating material, each of said sheets being bent into the tubular configuration of said liner and having an overlapped seam extending the length of said liner at the top of the slot, bonding means forming the overlapped seam in said outer sheet into a substantially moisture-proof joint along its entire length, said inner sheet having its overlapping seam inside the inner wall of said outer sheet.
9. An apparatus as recited in claim 8 wherein said inner sheet extends beyond the length of said outer sheet at each end thereof.
References Cited in the file of this patent UNITED STATES PATENTS 2,495,010 Kirkpatrick Jan. 17, 1950 FOREIGN PATENTS 1,243,701 France Sept. 5, 1960