Abstract:
A multi-pole generator rotor and a method of making the same are disclosed. A multi-pole generator rotor includes a rotor body having a central portion with a generally cylindrical outer surface. The outer surface includes three pairs of diametrically opposed slots extending along a length of the central portion, with each of the slots being sized to receive therein a plurality of wires. Each of the slots further includes a pair of opposed retaining flanges. A plurality of retaining members are sized for insertion into a corresponding one of the slots. Each retaining member engages a pair of the retaining flanges from its corresponding slot. The retaining members thereby retaining the wires disposed in each slot against radially outward displacement. A method of forming a multi-pole generator rotor includes the steps of providing the above rotor body, winding first, second and third wire coils by repeatedly winding a wire through a first, second, and third set of opposing slot pairs, and inserting a retaining member longitudinally into each of the slots.

Description:
FIELD OF THE INVENTION 
     The present invention relates to generator rotors, such as multi-pole generator rotors suitable for high speed applications. 
     BACKGROUND OF THE INVENTION 
     Feasibility investigations suggest that power generators for aircraft and spacecraft may be constructed using highly efficient magnetic bearings. However, these same investigations suggest that weight effective designs can be achieved only with very high speed applications. Typical power generators, such as power generators found in aircraft, operate in the range of 24,000 rpm, and typically employ the pole configuration illustrated in FIG. 8 of the drawings. One problem encountered by the typical configuration shown is that at high rpm&#39;s the resulting high centrifugal forces causes a radially outward displacement of the end-turns of the winding. This outward displacement causes the rotor to go out of balance and also creates the potential for field failure. Moreover, the sharp turns encountered by the wire on the region of the pole tip limits the gauge of wire that may be employed. Thus, it would be desirable to develop an improved winding system and an improved rotor design which would be operable at high speeds. 
     SUMMARY OF THE INVENTION 
     A six pole generator construction having an odd number of pole pairs constructed according to the teachings of the present invention will have a design speed of 50,000 rpm with an overspeed in the range of 55,000 rpm. 
     According to a first aspect of the invention, a multi-pole generator rotor comprises a rotor body including a central portion having a generally cylindrical outer surface. The outer surface includes three pairs of diametrically opposed slots extending along a length of the central portion, with each of the slots being sized to receive therein a plurality of wires. Each of the slots further includes a pair of opposed retaining flanges. A plurality of retaining members are sized for insertion into a corresponding one of the slots, with each retaining member engaging the opposed retaining flanges of its corresponding slot. The retaining members thereby retain the wires disposed in each slot against radially outward displacement. 
     In further accordance with a first aspect of the invention, the rotor body is rotatably mounted to a generator housing, and a continuous wire winding is wound upon the rotor body such that a plurality of wire sections is disposed in each of the slots. The rotor body includes a pair of ends connected by a central axis, and the wire winding includes a plurality of end portions adjacent each of the rotor body ends. Each of the wire winding end portions crosses the rotor body central axis, and an end support mounted to each of the rotor body ends supports the adjacent wire end portions. Preferably, the end supports include a plurality of aligning prongs, such as six aligning prongs. Still preferably, a cap member is mounted to each of the rotor body ends, with each of the cap members engaging an adjacent end support. 
     Preferably, each cap member also engages the end portions of the adjacent retaining members, thereby preventing longitudinal movement or displacement of the retaining members. 
     Preferably, the rotor body is mounted to a shaft, which shaft is rotatably mounted within a generator housing. Each of the cap members may include three intersecting grooves, with each of the grooves being sized to overlie an adjacent wire end portion. Each of the slot retaining flanges may include an angled surface, and each of the retaining members includes a wedge shaped edge. Each wedge shaped edge is sized to engage an adjacent angled surface, thereby securing each retaining member against radially outward displacement. 
     In accordance with a second aspect of the invention, a multi-pole generator rotor for receiving a continuous wire winding comprises a rotor body having a generally cylindrical central portion, with the central portion including a plurality of slots extending along the length thereof. Each of the slots is sized to receive a portion of the wire winding. Each of the slots further includes a pair of longitudinally extending edge portions, with each of the edge portions defining a retaining flange. A plurality of retaining members are provided, with each retaining member being sized for insertion in a corresponding one of the slots. Each of the retaining members includes a pair of edges sized to engage the edge portions of its corresponding slot. Thus, the wire winding portion disposed in each slot is held in a fixed position by the corresponding retaining member. 
     In accordance with another aspect of the invention, a multi-pole generator rotor comprises a rotor body having a generally cylindrical central portion, with the central portion including six slots extending along the length thereof. Each of the slots includes a pair of longitudinally extending edge portions, with each of the edge portions defining a retaining flange. A continuous wire winding is wound about the rotor body and defines three pole pairs, with each of the pole pairs engaging diametrically opposite slots. Six retaining members are provided, with each of the retaining members being sized for insertion in a corresponding one of the slots. Each of the retaining members includes a pair of edges sized to engage the adjacent retaining flanges. Accordingly, a portion of each coil disposed in each of the slots is held in a fixed position by the corresponding retaining member. 
     In accordance with a still further aspect of the invention, a multi-pole generator rotor comprises a rotor body including a central portion having a generally cylindrical outer surface. The outer surface includes at least one pair of diametrically opposed slots extending along a length of the central portion, with each of the slots being sized to receive therein a plurality of wires. Each of the slots further includes a pair of opposed retaining flanges. A plurality of retaining members are sized for insertion into a corresponding one of the slots, with each retaining member engaging the opposed retaining flanges of its corresponding slot. The retaining members thereby retain the wires disposed in each slot against radially outward displacement. Preferably, the rotor body outer surface may have an odd number of slot pairs. 
     In accordance with yet another aspect of the invention, a method of forming a multi-pole generator rotor comprises the steps of providing a rotor body having a cylindrical central portion and a plurality of diametrically opposed slot pairs defined in the central portion, with each of the slots in each slot pair extending along the length of the central portion. A first coil is formed by repeatedly winding a wire through a first of the plurality of slot pairs, a second coil is formed by repeatedly winding a wire through a second of the plurality of slot pairs, and a third coil is formed by repeatedly winding a wire through a third slot pair. A retaining member is inserted longitudinally into each of the slots. 
     Preferably, an end cap is secured to opposite ends of the rotor body. Further, each of the coils includes opposing end portions, and a coil support is inserted between each of the end caps and the adjacent coil end portions. Still preferably, opposing end portions of each of the coils are supported during winding. Each of the retaining members may be secured against longitudinal movement, such as by the end cap. The end cap is preferably sized to receive the adjacent coil end portions. Support for the rotor body and the end caps may be provided by shrink forming a retaining sleeve about the rotor body. 
     Additional features and advantages of the present invention will become readily apparent to those skilled in the art upon reading the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded fragmentary view in perspective of a multi-pole generator rotor and associated components all constructed in accordance with the teachings of the present invention; 
     FIG. 2 is an enlarged cross-sectional view of the rotor body having a plurality of wire sections disposed in one of the slots; 
     FIG. 3 is an end view of the rotor body having the end support attached and having three wire coils formed thereon; 
     FIG. 4 is a perspective view of a wire winding end support; 
     FIG. 5 is a perspective view of an end cap for placement over the end support; 
     FIG.  6 . is a fragmentary cross-sectional view of a power generator having a rotatable rotor body assembled in accordance with the teachings of the present invention and shown mounted for rotatable movement inside a generator housing; 
     FIG. 7 is an enlarged view in perspective of one of the retaining members; and 
     FIG. 8 is an enlarged fragmentary view in perspective of a conventional wire wound generator pole constructed in accordance with the teachings of the prior art; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments described herein are illustrative and are not intended to limit the invention to precise forms disclosed. Rather, the embodiments have been chosen and described in order to best enable those skilled in the art to follow the teachings of the present invention. 
     Referring now to the drawings, a multi-pole generator rotor assembled in accordance with the teachings of the present invention is generally referred to by the reference numeral  10 . As shown in FIGS.  1  and  2 , the generator rotor  10  includes a rotor body  12  having a central portion  14  having a generally cylindrical outer surface  16 . The rotor body  12  includes a pair of ends  13 ,  15  (the end  15  of the rotor body  12  is viewable only in FIG. 6, but as is explained below, the end  15  is substantially similar to the end  13 ). The outer surface  16  includes a plurality of longitudinally extending slots  18 ,  20 ,  22 ,  24 ,  26  and  28 , which are arranged circumferentially about the outer surface  16  of the rotor body  12 . For purposes which will be explained below, each of the slots is paired with a diametrically opposite slot, i.e., the slot  18  is paired with the slot  24 , the slot  20  is paired with the slot  26 , and the slot  22  is paired with the slot  28 . 
     The slots  18 ,  20 ,  22 ,  24 ,  26  and  28  are adapted to receive therein a continuous wire winding  30  which is wound about the rotor body  12  to form three wire coils  32 ,  34  and  36  as shown in FIG.  3 . The first coil  32  is disposed in the slot pair  18  and  24 , the second wire coil is disposed in the slot pair  20  and  26 , while the third wire coil is disposed in the slot pair  22  and  28 . It will be appreciated that the coil  32  has a negative pole disposed in the slot  18  and a positive pole disposed in the slot  24 , the coil  34  has a negative pole disposed in the slot  26  and a positive pole disposed in the slot  20 , and the coil  36  has a negative pole disposed in the slot  22  and a positive pole disposed in the slot  28 . Each of the coils  32 ,  34  and  36  is disposed parallel to and lying along a central axis  60  of the rotor body  12 . 
     It will be understood that the structure of each of the slots  18 ,  20 ,  22 ,  24 ,  26  and  28  is identical. However, only the structure of the slot  18  will be described herein in detail. The slot  18  includes a bottom wall  18   a , and a pair of opposing sidewalls  18   b  and  18   c . A portion of the sidewalls  18   b  and  18   c  include a lip or flange  18   d ,  18   e , respectively. The flanges  18   d  and  18   e  each include an angled surface  18   f ,  18   g , respectively. The slot is sized to receive therein a plurality of wire sections  38  from the positive pole of the first wire coil  32 . It will be understood that a similar wire section from the negative pole of the first coil  32  is disposed in the slot  24 . Further, wire sections from each of the second and third coils  34 ,  36 , reside in the slot pair  20  and  26  and in the slot pair  22  and  28 , respectively. 
     A plurality of retaining members  40  are provided, one of which is viewable in FIG.  2  and which is also shown in FIG.  7 . Although only a single retaining member  40  is shown or described in detail, it will be understood that a retaining member  40  will be provided for each of the slots  18 ,  20 ,  22 ,  24 ,  26  and  28 . Each retaining member  40  includes a radially inward or bottom surface  42  and a pair of angled or wedge shaped edges  44 ,  46  extending between a pair of ends  48 ,  50 . Each retaining member  40  also includes a radially outward surface  52 , which is preferably curved to match the outer surface  16  of the central portion  14  of the rotor body  12 . 
     Referring now to FIG. 1, each of the coils  32 ,  34  and  36  includes a pair of end portion  54 ,  56  and  58 , respectively, disposed adjacent each of the ends  13 ,  15  of the rotor body  12 . Although only the end portions  54 ,  56  and  58  adjacent to the end  13  of the rotor body  12  is shown, it will be understood that the end portions disposed adjacent the end  15  of the rotor body  12  are identical. As shown in FIG. 1, the end portion  56  of the coil  34  overlies the end portion  54  of the coil  32 , and the end portion  58  of the coil  36  overlies the end portion  56  of the coil  34 . Each of the end portions  54 ,  56  and  58  crosses the central axis  60  of the rotor body  12 . 
     Referring now to FIGS. 1 and 4, an end support  62  includes three diametric slots  64 ,  66  and  68 , which are separated by six aligning prongs  70 ,  72 ,  74 ,  76 ,  78  and  80 . The end support  62  is preferably constructed of plastic and is generally round. Each of the aligning prongs  70 ,  72 ,  74 ,  76 ,  78  and  80  includes a generally triangularly shaped cross section. An end support  62  is mounted to each of the ends  13 ,  15  of the rotor body  12 , such that the end portion  54  of the coil  32  is disposed in the slot  64 , the end portion  56  of the coil  34  is disposed in the slot  66 , and the end portion  58  of the coil  36  is disposed in the slot  68 . Further, the aligning prongs  70 ,  74 ,  76  and  80  align the end portion  54  of the coil  32 , the prongs  70 ,  72 ,  76  and  78  align the end portion  56  of the coil  34 , and the prongs  72 ,  74 ,  78  and  80  align the end portion  58  of the coil  56 . Each end  13 ,  15  of the rotor body  12  may include a circular depression or seat  82 , which is sized to receive the circular base  84  of the end support  62 . 
     Referring now to FIGS. 1 and 5, an end cap  86  includes three radially extending flange portions  88 ,  90  and  92 , separated by three cutouts  94 ,  96  and  98 . The end cap is preferably plastic. An end cap  86  is preferably mounted to each of the ends  13 ,  15  of the rotor body  12  in a position to generally overlie the adjacent end support  62  as will be explained below. Accordingly, two such ends caps  86  will be provided, although only a single end cap  86  will be described in detail. Terminals (not shown) are provided in one of the caps  86  in order to provide electrical connection to the winding as would be known to those of skill in the art. 
     The end cap  86  includes three grooves  100 ,  102  and  104 . The groove  100  is sized to abut or overlie the end portion  54  of the coil  32 , the groove  102  is sized to abut or overlie the end portion  56  of the coil  34 , and the groove  104  is sized to abut or overlie the end portion  58  of the coil  36 . As can be seen in FIG. 5, each of the grooves  100 ,  102 ,  104  is shaped to match the shape or curvature of their corresponding coil end portions  54 ,  56  and  58 , respectively. The groove  100  terminates near two diametrically opposed edge portions  100   a  and  100   b , the groove  102  terminates near a pair of diametrically opposed edge portions  102   a  and  102   b , and the groove  104  terminates near a pair of diametrically opposed edge portions  104   a  and  104   b.    
     When a cap  86  is secured to the end  13  of the rotor body  12 , the edge portions  100   a ,  100   b  will abut and thus secure the adjacent ends  48  of the retaining member  40  disposed in each of the slots  18  and  24 . Similarly, the edge portions  102   a ,  102   b  will abut a retaining member  40  disposed in each of the slots  20 ,  26 , while the edge portions  104   a ,  104   b  will abut a retaining member  104   a ,  104   b  disposed in each of the slots  22 ,  28 . A cap  86  secured to the end  15  of the rotor body  12  will abut the adjacent ends  50  of the corresponding retaining members  40  in the same manner. 
     Each of the caps  86  further includes three recesses  106 ,  108 ,  110  which are sized to receive one of the aligning prongs, such as the aligning prongs  80 ,  72 , and  76 , respectively. It will be appreciated that the remaining aligning prongs  70 ,  74 ,  78  will be disposed in a corresponding one of the cutouts  94 ,  98  and  96 , respectively. 
     As shown in FIG. 1, a rotatable shaft  112  having three prongs  114 ,  116  and  118  is mountable to the rotor body  12  so as to secure the cap  86  in pace. The prongs  114 ,  116  and  118  fit through the recesses  94 ,  98  and  96 , respectively. The prong  114  is mountable to the rotor body  12  between the slots  18  and  20 , the prong  116  is mountable to the rotor body  12  between the slots  22  and  24 , and the prong  118  is mountable to the rotor body between the slots  26  and  28 . The shaft  112  is connected to other components of the generator, such as an exciter and other required components as would be known to one of skill in the art. A support shaft (not shown) is mounted to the other end  15  of the rotor body  12  in a similar manner. 
     In operation, an end support  62  is positioned adjacent each of the ends  13 ,  15  of the rotor body  12  with the base  84  of each support  62  disposed in the seat  82  adjacent each end  13 ,  15 . The coils  32 ,  34   36  are then wound upon the rotor body using a conventional armature winding machine. Slots or grooves may be provided in the end supports  62  to facilitate crossover between coils to ensure proper current direction. 
     It will be appreciated that a heavier/stiffer gauge of wire may be employed due to the more gradual curvature required when winding the wire longitudinally about the rotor body  12  as compared to the sharp turns required by the prior art approach shown in FIG.  8 . The coils  32 ,  34  and  36  are wound in succession using a continuous wire, and the end portions  54 ,  56 , and  58  are disposed in the slots  64 ,  66 ,  68 , respectively, and are supported by their adjacent aligning prongs  70 ,  72 ,  74 ,  76 ,  78  and  80 . 
     Upon the completion of the coil winding, a retaining member  40  is inserted longitudinally into the slot  18 . The bottom surface  42  overlies and secures the wire sections disposed in each of the slots, such as is shown in FIG.  2 . The wedge shaped edges  44 ,  46  extending between the ends  48 ,  50  engages the adjacent angled surfaces  18   f ,  18   g  of the flange  18   d  and  18   e , respectively. The wire section  38  is thus confined on two sides by the slot sidewalls  18   b  and  18   c , and is held to the slot bottom wall  18   a . Additional retaining members  40  are inserted into each of the remaining slots  20 ,  22 ,  24 ,  26  and  28  in a similar manner. 
     Upon insertion of the retaining members  40 , an end cap  86  is placed over each end  13 ,  15  of the rotor body  12 , such that each end cap  86  interlocks with and engages the adjacent end support  62  and the three coils  32 ,  34 ,  36  in the manner described above. The end supports  62  ensure proper layering of the wire sections in the region of the end turns. Each tier of wire is wound over the previous tier. The retaining members  40  are secured against longitudinal movement by the edge portions  100   a ,  100   b ,  102   a ,  102   b ,  104   a , and  104   b  of the caps  86 . The retaining members  40 , the end supports  62  and the end caps  86  ensure precise support of the winding during high speed operation, i.e., the retaining members  40  prevent radially outward displacement of the wire sections  38  disposed in each of the slots, while the end supports  62  and the end caps  86  prevent lateral or radially outward movement or displacement of each of the wire end portions  54 ,  56  and  58 . 
     The rotatable shaft  112  and the support shaft (not shown) are then connected, and the rotor  10  is ready for insertion into the generator  122  shown in FIG.  6 . The rotor  10  is preferably housed in a stainless steel or composite cylinder  124  into which cooling oil is injected under pressure in order to cool the winding of the coils  32 ,  34  and  36 . The cylinder  124  is preferably sized to fit very tightly around the outer circumference of the rotor body  12  in order to provide mechanical support for the rotating components. This may be accomplished by shrink fitting the outer cylinder  124  around the rotor  10  as a last step after the assembly of the coils  32 ,  34  and  36 , the attachment of the end supports  62  and the caps  86  and the attachment of the shaft  112 . The cylinder  124  also serves to longitudinally confine the shaft  112  as well as the caps  86 . A plurality of grooves or slots  120  are provided about the periphery of the outer surface  16  of the rotor body  12  as shown in FIG. 2 to facilitate oil circulation. 
     Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.