Abstract:
A method for winding a stator of a multi-phase motor includes successively winding each of a plurality of teeth on the stator with a continuous winding wire to connect each of the phases in the motor together. The wound wire is disconnected between any two phases where respective ends of the two phases connected by the winding wire are not neutral ends. A jumper wire is connected between a neutral end of any one of the phases to a neutral end of at least one other phase if the neutral end of any one of the phases is not connected to the neutral end of at least one other phase by the winding wire.

Description:
This Application claims the benefit of U.S. Provisional Application No. 60/455,976, filed on Mar. 19, 2003. 

   BACKGROUND OF THE INVENTION 
   The present invention generally relates to multiple phase electric motors, and more particularly to the winding of coils during the manufacture of such motors. 
   Conventional brushless permanent magnet servomotor designs that are common in the marketplace include 4-pole rotor-12 slot stator motors; 4 pole-24 slot motors; 6 pole-18 slot motors; and 6 pole-36 slot motors, for example. An illustration of an 18-slot stator  10  is shown in  FIG. 1 . A typical winding pattern for two phases (U and V) of an 18-slot stator is shown in  FIGS. 2 and 3 . Because of the crossovers  12  of coils in the ends of the stator  10 , the winding end-turns  14  tend to be long and bulky and add considerably to the winding resistance in the winding pattern shown in  FIG. 2 . This reduces the motor torque density. Also, in order to produce motors capable of running off servo amplifier bus voltages up to approximately 680 V DC, inter-phase insulation paper  16  must be routed between the coils of adjacent phases. 
   To avoid these issues many manufacturers have adapted motor topologies using single-tooth winding, so that each coil has a span of one lamination tooth. In order to utilize this topology, the ratio of motor slots to poles (S/P) must lie in the range of 0.5&lt;S/P≦1.5. Single tooth winding significantly reduces the height of the winding heads  14  and eliminates crossovers  12  between coils of different phases, as shown in  FIG. 4 . 
   Two design classes are practiced in the construction of single tooth windings, the first being single piece lamination with needle winding and the second being segmented stators. With regard to the single piece lamination with needle winding, this practice has the advantage that the stator laminations are whole or single piece, allowing easier assembly of the stator pack. Prestack stator packs are desirable for volume production. The windings are placed in the slots with a needle winder which somewhat restricts the available winding space. 
   With regard to the segmented stator winding practice, there are many variations on this theme but all involve a segmented stator pack. The windings are wound in very high density either directly on the tooth or on separate bobbins and subsequently transferred onto the tooth. Bobbin winding requires some sacrifice of available winding area in order to get good layering, but very high density windings can be achieved. There is, however, an extra step of recombining the stator segments after winding placement. 
   Stator connection refers to the process of linking all the coils in each of the phases. In a three-phase stator connection, a star-point is formed from the ends of the coils of each phase and the starts of the three phases are brought to the outside world as shown in  FIG. 5 . For small motors it is commonplace to terminate the start and finish of each coil on terminal posts. 
   SUMMARY OF THE INVENTION 
   One embodiment of the present invention relates to a method for winding a stator of a multi-phase motor. The method includes successively winding each of a plurality of teeth on the stator with a continuous winding wire to connect each of the phases in the motor together. The wound wire is disconnected between any two phases where respective ends of the two phases connected by the winding wire are not neutral ends. A jumper wire is connected between a neutral end of any one of the phases to a neutral end of at least one other phase if the neutral end of that any one of the phase is not connected to the neutral end of that at least one phase by the winding wire. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an 18-slot stator; 
       FIG. 2  is a diagram illustrating a conventional winding configuration for an 18-slot stator of a three-phase motor; 
       FIG. 3  is a diagram stator of a wound according to the winding configuration shown in  FIG. 2 ; 
       FIG. 4  is a perspective view of a stator with windings that have been wound with a needle winder; 
       FIG. 5  is a circuit diagram illustrating the connections of phases in a three-phase motor; 
       FIG. 6  is a top view of a 9-slot stator illustrating a stator winding pattern in accordance with an embodiment of the invention; 
       FIG. 7  is a perspective view of a representation of the wound 9-slot stator shown in  FIG. 6 ; 
       FIG. 8  is another perspective view of the representation of the wound 9-slot stator shown in  FIG. 6 ; 
       FIG. 9  is a diagram illustrating the winding pattern of the 9-slot stator shown in  FIG. 6 ; 
       FIG. 10  is a diagram illustrating a winding pattern of a 12-slot stator shown in accordance with another embodiment of the present invention; 
       FIG. 11  is a top view of the 12-slot stator wound in the pattern shown in  FIG. 10 ; and 
       FIG. 12  is a diagram showing the electrical connections of the phases of the 12-slot stator wound as shown in  FIG. 10 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is generally directed to a class of stator windings that has a stator tooth to rotor pole ratio (S/P) that is within the range of about 0.5 to 1.5. The invention can also be used with a stator designed for operation of the motor having voltage drive up to approximately 680 V DC. 
   Referring to  FIGS. 6–9 , a 9-slot stator  18  for a motor having 6 rotor poles (not shown), for example, is shown in accordance with one embodiment of the present invention. The stator  18  is generally adapted to be used for smaller motors, typically, but not limited to less than 100 mm diameter, and includes nine teeth  20 – 36  and nine slots  38 – 54  each provided between a pair of teeth (best shown in  FIG. 6 ). 
   The stator  18  is also provided with an attached front-end insulator  56  and a rear end insulator  58  (best shown in  FIGS. 7 and 8 ) which, in one embodiment, is formed from molded engineered thermoplastic or similar material known in the art. The rear end insulator  58  features a number of recessed pockets  60 , through which a wire is routed for purposes of forming a connection by inserting a terminal into the pocket to provide an insulation displacement connection (IDC) and/or an interface termination at this point in the winding. The rear end insulator  58  also includes a system of slits having three different depths  64 ,  66 ,  68  (best shown in  FIGS. 7 and 8 ) as an integral part of the molding. These slits  64 ,  66 ,  68  provide a mechanism for physically and electrically separating the sections of wire between successive coils  70  from each other, in order to provide a winding that has the capability to withstand high voltage. 
   A pattern for winding the stator  18  in accordance with one embodiment of the invention is now described. The arrows in  FIGS. 6 and 9  indicate the direction in which the wire is wound around the teeth  20 – 36 . In one embodiment, the stator  18  is wound using a needle winder. Use of “in slot” winder or wire shooter are also contemplated. Referring to  FIGS. 6 and 9 , winding of the coils  70  starts at the slot  38 , where a winding wire  72  representing a lead end U of a first phase is inserted through an IDC pocket  60  near the slot  38 , and wound around the tooth  20  (between slots  38  &amp;  40 ) in a clockwise sense. The wire  72  exits through the deepest end insulation slit  64  of the rear end insulator  58  at the slot  40  (see  FIG. 7  or  8 ). The winding wire  72  then loops over to the slot  44 , routing the wire through the deepest end insulator slit  64  at the slot  44 . The wire  72  is wound clockwise around the tooth  26 , exiting through the deepest end insulation slit  64  at slot  46 . The wire  72  then loops over to the slot  50 , again routing the wire through the deepest end insulator slit  64 . The wire  72  is then wound clockwise around the tooth  32 , exiting through an IDS pocket  60  at the slot  52 . This point corresponds to the neutral end N of phase  1  in the winding scheme. 
   Without interrupting the winding route, the wire  72  is routed through another IDC pockets  62  at the slot  52  (see  FIG. 6 ). This section of winding wire  72  will later be sheared off in a post winding operation such that the winding reentry through the second IDC pocket  60  at the slot  52  now represents the start of phase  2 , i.e., the lead end W. The winding wire  72  is wound around the first coil of phase  2  clockwise around the tooth  34 , and routed out through the mid-depth slit  66  (best shown in  FIG. 8 ) in the rear end insulator  58  at the slot  54 . The wire  72  is then looped around the outside of the rear end insulator  58  and routed into the slot  40  through the mid-depth slit  66  at the slot  40 , and wound around the tooth  22  in the clockwise direction. The winding wire  72  is then routed through the mid-depth slit  66  at the slot  42  and looped around the outside of the rear end insulator and through another mid-depth slit  66  at the slot  46 , where it is wound around the tooth  28  in a clockwise direction, and exits through the mid-depth slit  66  at the slot  48 . This position now corresponds to the neutral end N of phase  2 . It should be noted that this, and subsequent section of the wire  72  overlaps a section forming phase  1 , but since the routing slits  64 ,  66  in the rear end insulator  58  are at two different depths, these wire sections are physically separated. 
   Routing the winding wire  72  through the IDC pocket  60  at the rear of the slot  50 , winding of phase  3  proceeds in reverse so that the current position corresponds to a joining of the neutral end N of phase  3  and the neutral end N of phase  2  (best shown in  FIG. 9 ). The winding wire  72  entering the slot  50  is wound around the tooth  30  in a counterclockwise direction and routed out of the slot  48  though the low-depth slit  68  (best shown in  FIGS. 7 and 8 ) formed in the rear end insulator  58  at the slot  58 . It should be noted that although this portion of winding overlaps a section of winding wire  72  for both phase  1  and phase  2 , a physical and an electrical separation are maintained by the different depths of the end insulator slits  64 , 66 , 68 , thus maintaining high voltage integrity. The winding wire  72  is then looped in a counterclockwise direction and inserted into the slot  44  through the low-depth slit  68 , where the winding wire is wound around the tooth  24  in a counterclockwise direction. Exiting through the low-depth slit  68  at the slot  42 , the winding wire  72  is then looped in a counterclockwise direction into the slot  38  through the low-depth slit  64  at the slot  34 , where the winding wire  72  is wound around the tooth  36  in a counterclockwise direction. Finally, the winding wire  72  is then routed through the IDC pocket  60  at the slot  54 . This point corresponds to the effective start of phase  3 , i.e., the lead end V. 
   Once the wire  72  has been wound around all the teeth  20 – 36  in the manner described above, the IDC terminal  62  are inserted into all five pockets  60  to cut the winding wire at these points. Then, the portion of the wire  72  between the two IDC pockets  60  at the slot  52  is sheared, i.e., between the neutral end N of phase  1  and the lead end W of phase  2 , as indicated by a dotted line in  FIGS. 6 and 9 . A jumper wire  74  is attached between the IDC pocket near the slot  50  and the IDC pocket near the slot  52  which is electrically connected to the tooth  32  (best shown in  FIG. 6 ). This step joins the neutral end N of phase  1  to the common neutral end N of phases  2  and  3  to make a star point connection as shown in  FIG. 5 . The remaining three IDC terminals  62  represent the termination interfaces or lead ends U, V, W of the three phases. 
   The present invention can also be described in connection with an embodiment shown in  FIGS. 10 and 11 , which is a stator  75  for a 10-pole rotor, 12-slot stator motor (not shown), for example. The stator  75  includes twelve teeth  76 – 98  and twelve slots  100 – 122 . This embodiment illustrates a winding pattern in which the individual coils  70  of a phase are not in simple series connection as in the embodiment described above. In this embodiment, with four coils per phase, the first pair of coils in series are parallel connected by jumper wires J 1 , J 2 , J 3  to the second pair of coils which are also series connected. Those skilled in the art will recognize that in this arrangement each phase will have two neutral ends N, one for each pair of coils. This embodiment represents a more complicated routing of the wires but nonetheless represents the same principle that was implemented in the embodiment described above. 
   More specifically, as shown in  FIGS. 10 and 11 , the stator  75  is wound starting with a lead end U of the winding wire  72  being inserted into a slot  100  through an IDC pocket  77  near a slot  122 . From this point, the wire  72  is wound continuously from the tooth  76  to the last tooth  98  in the directions indicated by arrows on the wire  72  in  FIGS. 10 and 11 . In the order from start to finish, the teeth of the stator  75  are wound in the following order: Beginning from tooth  76  to  78  to  82  to  80  to  84  to  86  to  90  to  88  to  92  to  94  to  96  and ending with tooth  98 . 
   A jumper wire J 1  is connected between the coils  70  formed from teeth  76  and  88  to establish a parallel connection between the two sets of coils in phase  1 . Similarly, a jumper wire J 2  is connected between the coils formed from teeth  80  and  92  to establish a parallel connection between the two sets of coils in phase  2 . In phase  3  a jumper wire J 3  makes the parallel connection between the coils  70  formed from teeth  84  and  96 . 
   A jumper wire J 4  is connected between one neutral end N of phase  2  (from the coil  70  formed from the tooth  94 ) and the first neutral ends N of phases  1  and  3  (the section of wire  72  extending between teeth  86  and  90 ). A jumper wire J 5  connects one neutral N of phase  3  (from the coil  70  formed from the tooth  98 ) and the second neutral ends N of phases  1  and  2  (the section of wire  72  extending between teeth  78  and  82 ). In this manner, each of the two neutral ends N in one of phases  1 – 3  are electrically connected to a respective neutral end N in the other two phases as shown in  FIG. 12 . 
   A section of the wire  72  (indicated in dashed lines in  FIGS. 10 and 11 ) connecting the coil  70  formed from the tooth  80  and the coil  70  formed from the tooth  84  is sheared to electrically isolate phases  2  and  3 . Similarly, a section of the wire  72  connecting the two coils  70  formed from teeth  88  and  92  are sheared to electrically disconnect phases  1  and  2 , and a section of the wire connecting the two coils formed from teeth  94  and  96  are sheared to electrically disconnect phases  2  and  3 . 
   In this embodiment also, the winding wire  72  is routed through the slits  64 ,  66 ,  68  with differing depth in the rear end insulator  58  (best shown in  FIGS. 7 and 8 ) to physically separate the wire between successive coils and between the phases. The recessed pockets  60  of the rear end insulators  48  are employed for purposes of forming IDC connections and lead ends in the winding. In this embodiment, the number of post winding jumpers to be inserted increases to  5 , the number of sections of winding wire  72  to be sheared off increases to  3  and the number of IDCs employed increases to  13  as shown in  FIGS. 10 and 11 . 
   While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. 
   Various features of the invention are set forth in the following claims.