Abstract:
An axial gap EDM deploys as a stator coils a series of two parallel serpentine windings that each circumscribe an arc segment of a circle. Each arc segment that forms the stator winding assembly is powered as a separate phase. The two winding are readily formed by shaping one or more wire segment. Preferably the parallel winding are arranged to overlap with a half period rotational offset such that the radial directed serpentine segments of that are disposed above and below the stator disk are interlaced when viewed in projection through the disk. In one embodiment, each series of serpentine winding are separated by a gap so that they can be inserted on the stator disk from the edge. A separate rotor disk is adjacent each side of this stator disk. In another embodiment, each series of serpentine winding are separated by a gap, so they can be inserted to surround a single rotor disk which has two series of magnets disposed on opposite sides.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    None 
       BACKGROUND OF INVENTION  
       [0002]    The present invention relates to axial gap electro-dynamo machines. 
         [0003]    Axial gap dynamo electric machines deploy stators and rotators that are generally in the shape of parallel and adjacent planar discs, with one of more rotators attached to an axle that passes though the center of each disk. 
         [0004]    The stator comprises multiple windings that generally wrap across the radial direction of the disc. A Lorenz force is generated by the interaction with magnets arranged along the periphery of the rotor disc. A more detailed description of this technology can be found in the U.S. Pat. No.&#39;s 4,567,391; 4,578,610; 5,982,069; and 5,744,896, all of which are incorporated herein by reference. 
         [0005]    The inventors have recognized that axial gap EDM&#39;s are ideally suitable for Vertical Axis Wind Turbine (VAWT) designs. VAWT offers a number of advantages over conventional Horizontal Axis Wind Turbine (HAWT), such as lower maintenance costs and increased durability and reliability. VAWT installations are believed to present a significantly lower hazard to migrating birds as HAVT systems, as well as 
         [0006]    While VAWT systems are also more economically viable in remote locations than 100+kW HAWT systems, there is an ongoing need to improve the efficiency of such machines as well as lower their capital cost so reduce the cost of electrical power derived from this renewable energy resource, and make small to medium size facilities more economically viable for say small communities or even the individual homeowner. 
         [0007]    Accordingly, it is a general object of the invention to improve the quality and economic viability of large scale axial gap electro-dynamo machines (EDM) for use as generators and motors. 
         [0008]    It is a more specific object of the invention to provide a more efficient method winding the stator coils of such generators and motors. 
         [0009]    It is an additional objective of the invention to provide a more efficient method of stator assembly for large scale axial gaps EDM&#39;s. 
         [0010]    It is a further objective of the invention to provide improved methods of thermal management of heat generated with the stator structure. 
         [0011]    It is a further objective of the invention to provide the above benefits at least in part through an improved efficiency through the concentration of the magnetic field with respect to it&#39;s interaction with the stator structure. 
       SUMMARY OF INVENTION  
       [0012]    In the present invention, the first object is achieved by providing an axial gap dynamo machine wherein the stator coil has an upper at least arc shaped serpentine wire segment, a lower at least arc shaped serpentine wire segment. Each serpentine path is made up of a series of connected wire segments in the order of a radial segment, an inner tangential segment, a second radial segment, an outer tangential segment. The upper and lower segments are joined at the periphery and spaced apart to provide a gap for a rotor plate having at least one sequence of magnets disposed in a common plane. 
         [0013]    A second aspect of the invention is characterized in that a plurality of arc shaped segment are inserted around the sides of the rotor disk to form a complete winding covering the rotor disk, with each segment connected as separate phase for power or rotary motion generation. 
         [0014]    Yet another aspect of the invention is the method of forming the arc shaped serpentine coil assemblies by first forming an insulated wire into a continuous coil and then wrapping the coil around at least one preform to form bends that define at least a portion of the serpentine path in at least one common plane. 
         [0015]    A still further aspect of the invention is the method of forming the stator structure or assembling a stator structure to surround the rotor disk by first encapsulating the arc shaped serpentine coil segments in a dielectric thermally conductive medium, such as fiber reinforced concrete. The arc shaped segments having a sideways U-shaped cross section are then inserted around the rotor disk. 
         [0016]    The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS  
         [0017]      FIG. 1  is a perspective view of a stator winding according to a first embodiment of the invention. 
           [0018]      FIG. 2A  is a cross-sectional elevation of the stator coil of  FIG. 1  showing the related rotor and attached axle structure. 
           [0019]      FIG. 2B  is a partial plan view of a portion of the stator winding. 
           [0020]      FIG. 2C  is an enlarged partial section through a wire that comprises the winding of  FIG. 1 . 
           [0021]      FIGS. 3A and 3B  are alternative embodiments for the arrangements of magnets on the rotor disk with an EDM having the stator coil shown in  FIG. 1   
           [0022]      FIG. 4  is a perspective view of a stator winding according to another embodiment of the invention. 
           [0023]      FIGS. 5A and 5B  are alternative embodiments for the arrangements of magnets on the rotor disk with an EDM having the stator coil shown in  FIG. 4 . 
           [0024]      FIG. 6  is an exploded view illustrating a preferred arrangement for locating the terminals of a stator winding of the type shown in  FIG. 1  or  FIG. 4   
           [0025]      FIG. 7A  is a cross-sectional elevation of a plurality of stator coils and related rotor structures according to another embodiment of the invention. 
           [0026]      FIGS. 7  B, C and D illustrate the three-phase wiring of the stator coils in  FIG. 7A . 
           [0027]      FIG. 8  is a schematic elevation comparing the available orientation of the magnets on the rotors for the embodiments of the three phase wiring with the stator windings shown in  FIG. 4 . 
           [0028]      FIG. 9  is a schematic elevation comparing the available orientation of the magnets on the rotors for the embodiments of the three phase wiring with the stator windings shown in  FIG. 1 . 
           [0029]      FIGS. 10A , B, C, D and E illustrates an embodiment of a preferred method of winding the stator coils. 
       
    
    
     DETAILED DESCRIPTION  
       [0030]    Referring to  FIGS. 1 through 10 , wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved axial gap EDM with an arcuate coil winding, generally denominated  100  herein. 
         [0031]    In accordance with the present invention,  FIG. 1  illustrates in perspective view a stator coil  100  with arcuate coil winding. The stator coil  100  subtends an arc of a circle to be assembled with additional stator coils as a disk shaped stator structure  250  as will be described in the FIG.&#39;s that follow with respect to alternative embodiments. 
         [0032]    Stator coil  100  comprises an upper arc shaped serpentine wire segment  120  and a lower arc shaped serpentine wire segment  110 , which are connected by at least one wire segment  25  that traverses the separate but parallel planes within which each of segments  110  and  120  are disposed. In each of the wire segments  110  and  120 , each serpentine path is made up of repeating series  105  of connected wire sub-segments in the order of a radial segment  5 , an inner tangential segment  10 , a second radial segment  15  and an outer tangential segment  20 . The electrical connections in this embodiment are made at terminals marked as phase (φ) and neutral (N) as the outer periphery of the arcuate coil segment  100 . A portion or segment of stator coil upper segment  120  is shown in Plan view is illustrated in  FIG. 2B , with separate reference arrow in each Figure indicating the radial (r) and tangential (t) coordinate axes. The X-axis corresponds to the principle axis of axle  10 . 
         [0033]    As the upper  120  and lower  110  segments are joined at the periphery by wire segment  25 , they are also spaced apart to provide a gap having the thickness represented by reference numeral  101  for inserting around either a rigid stator plate or a rotor plate having magnets. 
         [0034]      FIG. 2A  illustrates an alternative embodiment of the invention of an axial gap EDM  200  with a plurality of stator coil  100  (shown only on the left side of the figure) surrounding a single rotor disk  205 . This rotor disk  205  in this embodiment has magnets  215  arrayed the upper side and magnets  215 ′ arrayed on the opposite or lower sides. It should be understood that it is the intention in the preferred embodiments that each stator disk  250  when assembled into the working EDM comprise a plurality of stator coils  110  assembled to surround at least one rotor disk  205 , as shown in cross-sectional elevation in  FIG. 2B . It is more preferable to first form a plurality of wedge of half circle stator disc  2100  by potting the dual layer stator coil  100 , and then slipped or inserted it edgewise with respect the dual layer rotor disk  205 . The rotor disk  205  is in a rotary co-axle connection to the axle  10  and having at the periphery of the upper  211  and lower  212  surface an array  210  of permanent magnets, portion of which are illustrated in a transverse of tangential cross-section in  FIGS. 3 and 5 . 
         [0035]      FIG. 2B  is a section view through a winding  130  in cross-section containing a plurality of insulated wire bundles  140 . It should be appreciated that wire  140  can be round, but is alternatively of a flat cross-section to form a ribbon like shape. Preferably each segment of the wire contains multiple insulated strands, each plural wound in the serpentine shape.  FIG. 2C  is a plan view of segment  105 .  FIG. 2C  represents a preferred embodiment wherein a thermally conductive dielectric potting or encapsulating media  150  surrounds at least the portion  5  and  15  of the stator coil shown in  FIG. 2B . Such a preferred form of an encapsulating media is fiber reinforced cement. In essence, it is more preferred that the cement that encapsulates the stator windings, when solidified form the stator disk itself. Alternatively, another disk provided onto which the stator coil is then attached, and then covered by cement. 
         [0036]    Alternative embodiments for arranging and orienting the permanent magnets of array  210  are shown in  FIGS. 3A and 3B . Each of these figures is an elevation facing the edge of the rotor structure with only the radial segments of the stator winding shown. The direction of current flow in each winding segment is represented by an “o” for current flowing backwards from the plane of the Figure (the X-t plane) an “x” representing current flowing forward from the plane of the Figure, that is toward the viewer. 
         [0037]    It first should be noted that the rotor requires that magnets are disposed in  2  overlapping layers. In  FIG. 3A  the magnets in the upper layer are stacked over the magnets in the lower layer. The magnets in the upper layer are denoted as  125  and the magnets in the lower layer are denoted  125 ′. In contrast in  FIG. 3B , the magnets in the upper layer are offset or staggered to lie in between in pair of adjacent magnets in the upper layer. 
         [0038]    In a first pair of overlapping pair of  225 , magnets the upper magnet is oriented with the North Pole, “N”, facing up. However, the lower magnet  125 ′ is inverted so that the North Pole now faces down. This orientation is necessary, as for example in the case of a motor, so that the current going into the plane in the upper coil segment  1215  exerts a force on the rotor disk, in interacting with magnet  215 , which is in the same direction as the opposite flowing current out of the plane in the lower coil segment  1125 . It should be noted that the current in the lower coil segment  1125  interacts with magnet  215 ′. 
         [0039]    However, in the configuration shown in  FIG. 3B , the upper and lower magnets can be oriented with there north poles facing the same direction, as the staggering of the upper magnets  215  with respect to the lower magnets  215 ′ avoid the simultaneous application of opposing forces on the rotor. 
         [0040]    In accordance with another embodiment of the present invention,  FIG. 4  illustrates in perspective view a stator coil with two arcuate coil winding  100 . Each arcuate or wedge shaped stator winding  100  and  100 ′ subtends a half circle and are mounted to straddle the disk shaped rotor structure  205  as will be described in the FIG.&#39;s that follow. 
         [0041]    Each of the stator coil  100  and  100 ′ in  FIG. 4  comprises an upper arc shaped serpentine wire segment  120  and a lower arc shaped serpentine wire segment  110 , which are connected by at least one wire segment  25  that traverses the plane separating the upper and lower half is curved to follow diagonal path across the curved X-t surface such that the upper and lower arc segments are offset laterally by a half repeat unit  105 . This offset is more apparent in  FIG. 5A , which is a cross sectional elevation of the X-r plane the relationship between the stator structure and the rotor magnets  215 . 
         [0042]    Thus,  FIGS. 5A and 5B  are elevations facing the edge of the rotor structure with only the radial segments of the stator winding shown. Again, the direction of current flow in each winding segment is represented by an “o” for current flowing backwards from the plane of the Figure (the X-t plane) an “x” representing current flowing forward from the plane of the Figure, that is toward the viewer. It should be noted that because of the transverse segment  25  the upper coil  120  and the lower coil  110 , the radial segments of each winding are laterally staggered in the tangential direction. This staggering provides for at least two alternative orientations of magnets  215 . 
         [0043]    In  FIG. 5A  a plurality of magnets  215  are arrayed adjacent to each other in a single layer. Each magnetic  215  is oriented with opposite polarity of the adjacent magnet  215 . In  FIG. 5B  the magnets are disposed in  2  overlapping layers with the magnets in the upper layer  215  are stacked over the magnets in the lower layer  215 ′. Because of the lateral staggering of the coil segments of opposing sides of the stator, the magnets  215  in the upper layer need not be oriented in the opposite orientation of the magnetic  215 ′ immediately below in the lower layer. This is in contrast to the configuration shown in  FIG. 3A  and provides the benefit of a more concentrated magnetic field to increase power of the motor or the efficiency of the EDM when operated as a generator. 
         [0044]      FIG. 6  is an exploded perspective view of the rotor structure in  FIG. 4  showing in more detail that a connecting wire segment  25  traverses between upper arc shaped serpentine wire segment  120  and a lower arc shaped serpentine wire segment  110  disposed in parallel planes spaced apart by gap  101 . The electrical connections in this embodiment are made at terminals marked as phase (φ) and neutral (N) as the outer periphery of the arcuate coil segment  100 . 
         [0045]      FIG. 7A  is a cross-sectional elevation of a plurality of stator coils and related rotor structures in an EDM according to another embodiment of the invention. Stacked stators labeled B, C and D surround a rotor having a plurality of rotor disks  205  connected by common axial  10 . Each of the  FIGS. 7  B, C and D illustrate the three-phase wiring of the stator coils in  FIG. 7A , with the plurality of three type B stators in  FIG. 7B  all being wired to the first phase of the power circuit. Likewise, In  FIG. 7C , the plurality of three type C stators in are all wired to the second phase of the power circuit. Further, as shown in  FIG. 7C , the plurality of three type D stators in are all wired to the third phase of the power circuit. This configuration simplifies the wiring connections at the terminals of each stator segment, and avoids the possibility of short circuit if the insulating layer of the wiring in any segment is damaged. In such case, it may be preferable to wire each of the three upper stator segments together in series, but for a terminal that connects across the upper and lower stator segments, with the lower three stator segments also being connected in series. In this case each of the assembled stator sets that surround a rotor in the completed EDM has a signal adjacent phase and neutral terminal connection. 
         [0046]      FIG. 8  is a schematic elevation showing one embodiment of the orientation of the magnets on the rotors  205  for the embodiments of the three phase wiring with the stator structure  250  shown in  FIG. 4 . Each of the rotors  205 ,  205 ′ and  205 ″ surrounded by a stator has an upper and lower set of magnets in the, each magnet is oriented with N pole facing up. On the terminal rotors  205   a  and  205   b  that only have a single magnet layer, each magnet is oriented with N pole facing up 
         [0047]      FIG. 9  is a schematic elevation of another embodiment showing an alternative orientation of the magnets on the rotors for the embodiments of the three phases of wiring with the stator windings shown in  FIG. 1 . Each of the rotors  205 ,  205 ′ and  205 ″ is surrounded by the stator  225  and has an upper  215  and lower  215 ′ set of magnets. Each upper set of magnet  215  is oriented with N pole facing up, while each lower set of magnets  215 ′ is oriented with the North Pole facing down. 
         [0048]      FIGS. 10A , B, C, D and E illustrate an embodiment of a preferred method of winding the stator coils into arc shaped segment using a preform as a guide or track for the wire and the bends or folds therein. First, as shown in  FIG. 10A  insulated wire  1001  is wound around a circular form to form a coil of predetermined diameter with a multiple coil segment so that it terminates preferably in adjacent end terminals  1010  and  1020 , forming loop  1030 . 
         [0049]      FIGS. 10B and 10C  are plan and elevation views respectively of one embodiment of preform type winding frame  1150  used to shape loop  1030  into the configurations shown in  FIG. 1  and  FIG. 4 . Winding frame  1150  is substantially circular plate  1151  having an inner series of pegs  1161  extending from at least one, and preferably both sides. At the periphery of circular plate  1151  is a second series of outer pegs  1162 , which as shown in  FIG. 10C , also extend to both sides of plate  1151 . It should be appreciated that the pegs are spatially arranged in a predetermined manner to be disposed at the bending or deflection points of the stator winding in configuration shown in  FIGS. 1 and 4 . Thus, the inner pegs  1161  are arranged closer to each other than the outer pegs  1162  to define the wedge shape of each winding segment. 
         [0050]    As shown in  FIGS. 10D  and E, in the next step, the insulated wire loop  1030  is next wound into a serpentine coil using a preform, such as the frame and pegs shown in  FIGS. 10B and 10C . Thus, it is intended that the pegs be used to bend and then route the wire coil  1030  into a serpentine coil shape by repeated wrapping around at least an arc of plate  1151 , first between outer peg  1162  and the nearest inner peg  1161 , then to the next adjacent inner peg, followed by tight wrapping to the next outer peg and so on in the same direction under the desired wedge angle is subtended. At this point, winding frame  1150  can be flipped so that winding proceed to the other side. Wrapping to the reverse side of frame  1150  is shown in  FIG. 10E . Alternatively, a segment can be folded over to form sideways facing U shape after wrapping on one side of frame  1150 . 
         [0051]    It should be appreciated that the above method is not limited to the form of the preform shown, but may use bend, wrap or compress the serpentine coil. 
         [0052]    While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be within the spirit and scope of the invention as defined by the appended claims.