TOROIDALLY WOUND GENERATOR/MOTOR

Abstract: A method and apparatus for a toroidally-wound core winding for use in electromechanical devices such as motors and generators. The stator core is slotted on its inner edge, so that each slot is capable of holding a plurality of windings. The core is toroidally wound through the slots. Toroidal, slotted end caps having a substantially planar face connected to the winding core and a curved face opposite the substantially planar face.

Description: TOROIDALLY WOUND GENERATOR/MOTOR Field of the Invention This invention relates to armature and field windings for electromechanical devices, and, more particularly, to a method of winding and apparatus for toroidally-wound armatures and fields. Background of the Invention Electromechanical devices such as motors and generators include a stationary, wound core called a stator and a rotatable wound core called a rotor. Typically for AC machines the stationary wound core is the armature. Typical generators or motors will utilize an annular or donut-shaped stator, shown in Fig. 2. A rotor is inserted in the bored center of the stator winding. Fig. 2 shows a traditionally wound stator 10. The stator has a core 12 which has an inner face 14, an outer face 16, a first side face 18 and a second side face 20 (not visible from Fig. 2) . The stator core 12 also forms slots, 22, 24, 26 and 28 on the inner face 14. These slots are typically capable of holding one or more conductors. The winding of most modern-day stator cores is achieved by winding conductors such as conductor 30 through a slot such as slot 22, across the first side face 18 of stator core 12, through a second slot such as slot 28, around the second side face 20 of the stator core, through either the same slot 22 or a different slot such as slot 24, around the first side face 18 of the stator core, and so on as shown in Fig. 2. Typical stator cores will have several conductor windings through each slot with a great deal of bulk on each side face 18 and 20 of the stator core. In an effort to minimize the amount of bulk of such windings and to put the windings in proper form, such windings are frequently manually pounded, shaped and laced. Moreover, the windings outside the slot contribute nothing to the performance of the machine, but add material and decrease efficiency. Generally, a toroidally-wound core for electromechanical devices, sometimes known as a Gramme winding as shown in U.S. Pat. No. 218,520, as known. In a Gramme-type winding, the core of the stator is substantially farther away from the rotors than the stator core of windings such as that shown in Fig. 1. The Gramme-type winding was intended and used primarily for direct current (DC) power, but has been replaced even for DC power uses by devices wound as shown in Fig. 2. Moreover, such prior art toroidal windings have disadvantages in that the windings may be unduly stressed at the corners formed by the winding core, which may include many laminations and have a substantial thickness. Summary of the Invention In accordance with the present invention, a method of winding a winding core is provided which includes slotting the core along its inner diameter in a plurality of locations around the entire circumference of the inner edge of the core. The method further includes toroidally winding conductors around the core such that the number of windings necessary for desired performance is inserted into each slot of the core as the conductor is wound around the core. Also disclosed is a toroidally- wound stator or rotor core comprising a core slotted along its inner edge and having toroidally-wound conductors wound around the core such that a number of windings is inserted into each slot. In the preferred embodiment, the winding core will be a two-pole device. Moreover, an end cap is shown which is substantially planar on one side and curved on the side exposed to windings. The end cap further has projections corresponding to the slots of the core, and winding terminals. Brief Description of the Drawings Fig. 1 is a drawing of a toroidally-wound slotted stator in accordance with the present invention. Fig. 2 is a drawing of a prior art traditionally wound stator in general use for electromechanical devices. Fig. 3 is a close-up view of an electromechanical device in accordance with the present invention. Fig. 4 is a front view of a core having an end cap showing a portion of the radial slots formed therein in accordance with the present invention. Fig. 5 is a cross-sectional view of a portion of a core having an end cap in accordance with the present invention along the line 5-5' in Figure 4. Fig. 6 is a cross-sectional view of a portion of a core having an end cap in accordance with the invention along the line 6-6' in Figure 4. Detailed Description of the Drawings Fig. 1 shows a winding of a stator for an electromechanical device in accordance with the present invention. The wound stator 40 includes an annular or donut-shaped stator core 44. This core has an inner face 46, an outer face 62, a front face 60 and a back face 64 (not visible) . Typically, the core is formed by stacking a series of laminations having substantially similar, toroidal faces to a desired thickness. In part to obtain faces 46, 60, 62 and 64 which are as smooth and flat as possible,, and in part so that the slots 48 (including slots 50, 52 and 54) are properly formed, the laminations are aligned with each other. The inner face 46 of the stator core forms a boring, in which the rotor is placed. This inner face 46 forms a number of slots around the inner circumference of the stator core, including slots 50, 52, and 54. A typical number of slots which may be formed on the inner edge of the stator core is 66, of which 44 may be used to receive the primary windings in a two-pole device. The number of slots may vary and 66 is a number presented by way of example only. The stator core as shown in Fig. 1 is wound as follows: A conductor winding 70 is wound through one of the slots located on the front face of the core, such as slot 50, around the back face of the stator core 64 in Fig. 1, around the outer face of the stator core 62, around the front face of the stator core 60, and back through an inner face slot. The conductor may be wound either through the same slot through which the previous winding was wound, in this case slot 50, or through an adjacent slot, such as slot 52. In the embodiment shown in Figs. 1 and 3, each winding of the conductor will typically be substantially parallel to the adjacent windings of the conductor along each face 46, 60, 62 and 64 of the stator core. The slots may also be skewed from the radial direction without deviating from the spirit of the invention. In the preferred embodiment, as shown in Fig. 1, two conductors, 70 and 72, will be wound around the largest portion of the stator core 44, as for a two- pole device. In the embodiment shown, two additional conductors 76 and 78 are wound around small portions of the stator core at locations opposite each other to provide, for example, a secondary power source. This winding procedure as described in this and the preceding paragraphs may be described as toroidal winding. As shown in Fig. 1, as conductors 70 and 72 are wound around the outer face 62 of the stator core, the conductors are exposed to the air. The lesser length of the wire needed in Fig. 1, as opposed to the length of wire needed using a winding such as the winding shown in Fig. 2, is evident from comparing the two figures. In Fig. 2, for a two-pole device, some windings will go nearly 180° around the stator core, for example from slots 32 to slot 34. One loop through these two slots would require a conductor of a length of approximately (2 *r) + (2*d) , where r equals the radius of the inner edge of the stator core and d equals the distance from the front to the back faces of the stator core. In contrast, each turn of the winding in accordance with the present invention will have a length approximately equal to the sum of the lengths of each face of the stator core 46, 60, 62 and 64. Since, for most stator cores, the length of front and back faces 60 and 64 will be substantially less than 2 times the inner radius of the stator core, substantial reductions in the length of the conductors needed for a two-pole device may be achieved. The use of a shorter conductor also results in less resistance loss. Hence, the machine uses less material and has higher efficiency. Such efficiencies may also be achieved for devices having more than two poles, although the improvement in efficiency will be reduced. The two-pole winding is presented herein by way of example only. Figures 4, 5, and 6 show an alternate embodiment of a winding core 40' in accordance with the present invention having an end cap 100 shown on the face corresponding to front face 60 in Fig. 1. Typically, the core will have a similar end cap on its opposite face, corresponding to face 64 (not shown) . The end cap will typically be constructed of plastic or other material capable of being molded into the shape shown. The bottom face of the end cap 102 will be capable of providing a substantially planar surface for contact with the laminated winding core. The end cap is comprised of a substantially toroidal section 110 corresponding to the substantially toroidal portion of the laminated winding core. Toroidal end cap portion 110 has projecting members 114 projecting towards the center of the end cap toroid. Projecting members 114 are positioned such that each one aligns over laminated core projections (e.g. 56 and 58 shown in Figures 1 and 3) . Fig. 4 shows a portion of the core with five windings 210 of conductor 70 inserted in slot 212. Figure 4 also shows sets of terminals 120, 130, 132, and 134 at locations which in the preferred embodiment correspond to the portion of the core adjacent to the beginning and end of each of the windings to be wound on the core. These beginning and ending points typically correspond to areas adjacent to projections 80', 82', 84' and 86 r from the laminated winding core. Each set of terminals 120, 132, and 134 will typically include a terminal 122 for receiving one end of a winding extending from projection 80' to projection 86', a second terminal 124 for receiving one end of a first winding extending from projection 82' to projection 80', and a third terminal 126 for receiving one end of a second winding extending from projection 82' to projection 80'. On one of the two end caps typically used with the winding core, terminals such as terminals 122 and 124 will receive metal contacts for electrically connecting the windings to the generator or motor circuit, or to various other circuits such as power or charging circuits. The other end cap of the winding core typically will not have metal contacts, but the terminals themselves may be used as spacers to hold the wound or unwound core on a planar surface such that any windings around the core will not directly contact the planar surface, avoiding damage to the windings. Sets of terminals 130, 132 and 134 will be similar to terminal set 120. In the preferred embodiment shown in Fig. 4, each terminal set 120, 130, 132 and 134 is positioned adjacent to winding end projections 140, 142-, 144 and 146, respectively. These projections differ from projections 114 in that the slots formed in projections 140, 142, 144, and 146 are wider and shallower than slots 114. Since the windings terminate in the vicinity of the terminal projections 140, 142, 144 and 146, narrow, deep slots such as slots 114 are not needed. The laminated winding core may have relatively shallower slots at positions corresponding to terminal projections 140, 142, 144 and laminated core. Figures 5 and 6 shows cross-sectional views of Figure 4 along lines 5-5' and 6-6' in Fig. 4. The left side of Fig. 5 shows end cap 100 having a surface 102 capable of substantially planar contact with laminated core 150. End cap 100 is secured to laminated core 150 through securing means such as a triangular projection 160 integrated with end cap 100 and having a surface 162 which secures the end cap to laminated core 150, as shown in Fig. 6. A multiple number of such projecting securing members may be used. Terminal projecting members 142, 144 and 146 will typically be located above the securing means in the preferred embodiment. With the securing means comprised of projections as shown in Fig. 6, the end caps may be snapped onto the laminated core. Fig. 5 also shows projection 114 and the inner surface of the slot to one side of projection 114, designated 172. Projection 114 is typically in an inverted-V shape. This inverted-V shape helps to guide the windings into the slots formed by the end cap and the corresponding slots of the laminated core. Fig. 6 shows a cross-section of terminals 122 and 124, previously described. The terminal projection 140 of laminated core 150 is circumscribed in part by inward projection 190 and the inner surface of the terminal projection, 180. The slot in the laminated core corresponding to the slot in the end cap shown in Fig. 6 is formed by projection 190' and inner surface 180'. As shown in Fig. 4, the inner surface of the end cap slot 180 is shorter than surface 172, since a full width slot is shown at surface 172 whereas a terminal end cap projection surface is shown at 180. Fig. 4 also shows five winding turns 210 positioned in the slot 212 formed by the laminated core and the end cap. The turns are wound around the top, toroidal portion of the end cap 110. The curved form of end cap top portion 110 helps relieve stress on the windings, which generally do not overlap on the upper surface of the end cap. End cap 100 also has recesses 212, 214, 216 and 218 which align with laminated core projections 80', 82', 84' and 86'. These recesses conform to the shape of the laminated core projections. These recesses are shaped for clamping the winding core to a winding machine. Each recess includes a curved fence portion to prevent the resin coating applied to the windings from contacting core projections 80', 82', 84' and 86'. An insulating coating 220, such as a 3M Scotchcast 5230 brand powder coating, coats the metal laminated core. This powder coating is preferable to paper or other insulating materials because the coating material is much thinner than these alternatives, enabling use of relatively narrow slots (e.g. 114 in Fig. 4) . The use of relatively narrow, elongated slots results in the windings being positioned substantially along a radial line corresponding to the radius of the toroid, the positioning shown in Fig. 4 at 210. The use of a relatively large number of relatively narrow slots accompanied by radial winding provides for improved cooling of the conductors in that more of the conductor surface contacts the core, helping to dissipate more heat. The slots will typically have a width greater than the width of the conductor to be wound in the slot and less than twice the width of the conductor to facilitate the radial winding. As shown in Figs. 3 and 4, the slots may be rounded at the bottom, but such rounding is meant to be included within the term "substantially rectangular." Through the use of slots, projections (e.g. 56, 58 as shown in Fig. 3, 114 in Fig. 4) minimize the air gap between the stator core and the rotor used in combination with the wound stator. The efficiency of the device is improved thereby. As shown in Fig. 3, each winding of each conductor 70, 72, 76 and 78 follows a virtually identical winding pattern around the stator core and along the radius of the stator ring. A similar pattern is shown in Fig. 4 at 210. The winding process may be easily automated for such a winding method, for example, by use of a digital winding machine. Typically, the windings for one pole oppose the direction of winding the opposing pole. It should be considered as within the spirit of the disclosed device that a toroidal winding as shown could also be used for a rotor, although the invention is described herein in terms of a stator.

Claims: WHAT IS CLAIMED IS: 1. The method for winding a core for an electromechanical device having at least two poles comprising the following steps: forming an annular core having a plurality of projections and slots, the projections and slots being located along the inner diameter with respect to the annular core; and toroidally winding at least one conductor for each pole on the core around the cross section of the core and substantially parallel to the radius of the core, such that a multiple number of turns of each winding of the conductor is inserted into one of the slots formed in the annular core, the turns positioned within the slots in a substantially radial line. 2. The method for winding in accordance with claim 1, wherein the annular core is toroidally wound such that at least some of the successive windings of each conductor do not overlap on the face of the core opposite from the slotted face of the core. 3. The method for winding in accordance with claim 1, wherein the slotting of the annular core is such that the slots are substantially rectangular in shape. 4. The method for winding the core in accordance with claim 1, wherein the width of each slot is approximately equal to the width of the conductor inserted . into the slot. 5. The method of claim 1 wherein the circumferential arc encompassed by each of said plurality of projections and slots formed in the annular core is approximately 5.5 degrees. 6. The method of claim 1, where the step of forming the annular core comprises aligning a plurality of core laminations, each of which has a plurality of slots, and joining the aligned laminations. 7. The method of claim 1, wherein a portion of the toroidal windings are wound in the direction opposite from the other toroidal windings. 8. The method of claim 1, wherein the step of toroidally winding at least one conductor further includes the step of repeating the windings in one slot before the windings are placed in another slot. 9. The method for winding a core for an electromechanical device having at least two poles comprising the following steps: slotting an annular core on the inner diameter of the core such that a plurality of radial projections and slots are formed which are substantially rectangular in shape, each slot having a width approximately equal to the width of a conductor to be inserted into the slot; toroidally winding at least one conductor for each pole on the core around the cross-section of the core, substantially parallel to the radius of the core, such that the windings of said conductor are inserted into each slot formed by the core in a substantially radial line. 10. The method of claim 9 wherein the step of toroidally winding at least one conductor further includes the steps of winding the conductor once through each slot of a pole, and winding the conductor a second time through each slot of the pole. 11. A wound core for an electromechanical device having at least two poles comprising: an annular winding core forming a plurality of projections and slots substantially parallel to the annular radius of the winding core, said slots and projections located on the inner face of said core, said slots having a width substantially similar to the width of a conductor to be inserted into said slots; and at least one toroidally-wound conductor for each pole of the winding core, wound around the winding core in a direction substantially parallel to the annular core radius such that each winding of each conductor is located in one of the slots formed in the annular winding core. 12. A wound core for an electromechanical device in accordance with claim 11, wherein each slot formed in the annular winding core has approximately five winding loops. 13. A wound core in accordance with claim 11, wherein each conductor is wound such that its windings do not overlap on the outer face of the core. 14.. A wound core in accordance with claim 11, wherein the core is wound such that a substantial portion of the surface area of each winding of each conductor is exposed to the surrounding environment on the outer face of the core. 15. A wound core in accordance with claim 11, wherein the slots formed on the inner face of the core are substantially rectangular in shape. 16. A wound core in accordance with claim 15, wherein the slots formed on the inner face of the core have a width greater than the width of the conductor and less than twice the width of the conductor. 17. A wound core in accordance with claim 11, wherein the annular winding core is comprised of slotted core laminations. 18. A wound core in accordance with claim 11, wherein the number of slots formed in the annular winding core is approximately 66, approximately 44 of which are opposed in approximately equal numbers. 19. A wound core in accordance with claim 11, wherein at least one of the toroidally wound conductors is wound in a direction opposite from at least one other toroidally wound conductors. 20. A method for winding a core for an electromechanical device having at least two poles comprising the following steps: forming an annular core having a plurality of projections and slots, the slots being located along the inner diameter of the core such that the projections and slots are substantially parallel to the radius of the core; connecting a toroidal end cap to each side of the annular core, each toroidal end cap having a first surface capable of substantially planar contact with an end of the annular core, each end cap having a second surface opposite said first surface having a substantially curved portion, each end cap having radial projections on its inner diameter corresponding to the projections located along the inner diameter of the annular core; - toroidally winding at least one conductor for each pole through a first slot of the annular core, a first slot of the toroidal end cap corresponding to said first slot of the annular core, around the curved portion of the first end cap, around the outer diameter surface of the annular core, around the curved portion of the second end cap, and through a slot formed in the second end cap corresponding to said first slot of the annular core, and toroidally winding said conductor through successive slots formed in the annular core and the first and second end caps in a manner similar to the manner of toroidally winding said conductor through said first slot of the annular core and the first and second end caps. 21. A method as in claim 20, wherein the slots formed in the annular core and first and second end caps have a width approximately equal to the width of the conductor. 22. A method as in claim 20, wherein the step of toroidally winding a conductor through a first slot comprises winding a conductor a multiple number of times through said first slot such that the multiple windings within each slot are positioned in a substantially radial line. 23. A method as in claim 20, wherein the circumferential arc encompassed by each projection and each slot formed in the annular core and first and second end caps is substantially similar to -the width of the conductor to be wound in said slot. 24. A method as in claim 22, wherein the number of windings in each slot is approximately five. 25. A method as in claim 20, wherein the projections formed in the toroidal end cap are wider at the surface which interfaces with the annular core than at the surface of the projection opposite the surface which interfaces the annular core. 26. A wound core for an electromechanical device having at least two poles comprising: an annular winding core forming a plurality of projections and slots substantially parallel to the annular radius of the winding core, said slots and projections located on the inner face of said core; first and second toroidal end caps, said first end cap connected to one side of said annular core, said second end cap connected to the opposite side of the annular core, each end cap having a first surface planarally interfacing with the annular core and having projections and slots substantially corresponding to the projections and slots of the annular core such that the projections and slots of each end cap are aligned with the projections and slots of the annular core when each end cap is connected to the core.

Inventors: GULBRANDSON WILLIAM E, O'MALLEY GARY B, GULBRANDSON, WILLIAM, E., O'MALLEY, GARY, B.
Applicants: ONAN CORP, ONAN CORPORATION
Application year: 1988
Main classification: H02K3
IPC codes: H02K3, H02K15