Abstract:
An automotive alternator including a rotor having a plurality of poles; a plurality of phases in operable communication with the plurality of poles; and a stator core in operable communication with the rotor, the stator having a number of slots defined by:
 
 S= ( P×PH )+(( M×PH ) +N )
where S=number of slots P=number of poles PH=number of phases M=a whole integer greater than or equal to 0 N=a whole integer selected from a group of integers ranging from, and including, 1 through the number of phases minus 1. A method for reducing magnetic noise in an automotive alternator includes selecting a number of poles, selecting a number of phases, selecting a number of stator core slots, the foregoing selections interacting in the automotive alternator to produce an order of frequency of a tangential force different than any multiple of the number of phases and different than an order of frequency of a radial force of the alternator.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Dynamoelectric machines are integral portions of many modem day assemblies including such things as automobiles. One type of a Dynamoelectric machine, known as an automotive alternator, converts mechanical energy produced by one source into electrical energy to be used as desired by the automobile. An automotive alternator is defined as any dynamoelectric machine, which converts mechanical energy into electrical energy to be used as desired by an automobile. While such desires are useful, the magnetic noise associated with the generation of the electrical energy is undesirable. For reasons well known to those of ordinary skill in the art, a stator core of a dynamoelectric machine is one of: 1) full pitch, i.e. the number of slots is equal to the number of phases of the machine multiplied by the number of poles of the machine; and 2) fractional pitch, i.e. the number of slots is a multiple of the number of phases of the machine. The present inventor has apprehended that in both configurations, radial forces and tangential forces of the operating machine combine to create a large force leading to undesirable magnetic noise from the machine.  
         [0002]     Dynamoelectric machines capable of operating more quietly would be well received by the art.  
       SUMMARY OF THE INVENTION  
       [0003]     Disclosed herein is an automotive alternator including a rotor having a plurality of poles; a plurality of phases in operable communication with the plurality of poles; and a stator core in operable communication with the rotor, the stator having a number of slots defined by:
 
 S= ( P×PH )+(( M×PH ) +N )
        where S=number of slots     P=number of poles     PH=number of phases     M=a whole integer greater than or equal to 0     N=a whole integer selected from a group of integers ranging     from, and including, 1 through the number of phases minus 1.        
 
         [0010]     Further disclosed herein is an automotive alternator including a stator, a rotor in operable communication with the stator, at least one conductor having a plurality of endloops and a plurality of slot segments, and an unusual number of slots formed in the stator, the slots including at least one slot populated by a number of slot segments different than a number of slot segments populating another of the slots.  
         [0011]     Yet further disclosed herein is a method for reducing magnetic noise in an automotive alternator. The method includes selecting a number of poles, selecting a number of phases, selecting a number of stator core slots, the foregoing selections interacting in the automotive alternator to produce an order of frequency of a tangential force different than any multiple of the number of phases and different than an order of frequency of a radial force of the alternator.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Refer to the drawings wherein like elements are numbered alike in the several figures:  
         [0013]      FIG. 1  is a schematic illustration of a conductor enabling the slot configuration as disclosed herein;  
         [0014]      FIG. 2A  is a schematic view of a first pass having six phases, each conductor being specially formed as disclosed herein;  
         [0015]      FIG. 2B  is a schematic view of a second pass having six phases, each conductor being specially formed as disclosed herein;  
         [0016]      FIG. 3  is another partial cross-sectional view using the winding pattern of FIGS.  2 A/ 2 B and where slot  37  and  43  have four conductors each in paired relation;  
         [0017]      FIG. 4  is a schematic view of a winding pattern;  
         [0018]      FIG. 5  is an illustration of conductor lead locations in a stator core;  
         [0019]      FIG. 6  is a schematic partial cross-sectional view of a stator core populated with conductors according to the winding pattern of FIGS.  2 A/ 2 B where slot  37  and  43  include only four conductors grouped into pairs;  
         [0020]      FIG. 7A  is a schematic view of a first pass for an alternate winding pattern;  
         [0021]      FIG. 7B  is a schematic view of a second pass for the alternate winding pattern of  FIG. 4A ;  
         [0022]      FIG. 8  is yet another alternative winding pattern using the winding of FIGS.  4 A/ 4 B where slots  37  and  38  have only four conductors;  
         [0023]      FIG. 9  is another alternative winding pattern where all passes skip the same slot, leaving it empty;  
         [0024]      FIG. 10  is a schematic cross sectional view of a prior art alternator;  
         [0025]      FIG. 11  is a schematic view of conductors nested in a prior art cascade winding pattern;  
         [0026]      FIG. 12A  is a schematic view of a dual wye winding;  
         [0027]      FIG. 12B  is a schematic view of a three phase wye winding. 
     
    
     DETAILED DESCRIPTION  
       [0028]     In order to combat the magnetic noise in dynamoelectric machines for use in more modern applications where the noise is problematic for consumer satisfaction, component interaction, etc. the present inventor has departed from the conventional wisdom of the full pitch and fractional pitch stator cores. The reasoning behind the departure is a recognition that the tangential force, caused by cogging torque of rotor poles as they pass each stator core tooth is additive with the radial force, caused by torque ripple. The reason these two forces are additive, and therefore combine to form a large force creating magnetic noise, is that for a full pitch winding, they both exhibit the same order of frequency, that is the number of poles times the number of phases and for a typical fractional pitch winding, they both exhibit an order of frequency which is a multiple of the number of phases. To minimize magnetic noise the number of slots in a stator core should be as taught herein, whereby the order of frequency of the tangential force and the order of frequency of the radial force will be as far removed from one another as practicable and preferably both not a multiple of the number of phases. In other words, noise can be reduced if it is ensured through careful selection of the number of poles, phases and slots to interact such that an order of frequency of a tangential force of the resulting alternator is different than any multiple of the number of phases of the alternator and different than an order of frequency of a radial force of the alternator.  
         [0029]     The above is achievable in a dynamoelectric machine by selecting a stator core slot configuration defined by:
 
number of slots=( P×PH )+(( M×PH ) +N )
        where P=number of poles     PH=number of phases     N=any one of a set of whole numbers inclusive     from 1 through the number of phases −1     and M=a whole integer greater than or equal to 0.        
 
         [0035]     As can be seen by the formula, the number of slots can never be equal to the number of phases times the number of poles or even a multiple of the number of phases times the number of poles. A stator is defined has having an unusual number of slots when the number of slots is not equal to, or a multiple of, the number of phases times the number of poles. For example, a stator having 3 phases and 12 poles is defined as having an unusual number of slots when the number of slots is not equal to 36, 72, 108, etc. The typical automotive alternator has three phases or six phases.  
         [0036]     One example of a stator core configured as taught herein is one in which M=0 and 85, 86, 87, 88 or 89 slots are utilized with a rotor having 14 poles and the machine including six phases. It will be recognized that such a number of slots does not agree with either a full pitch system or a fractional pitch system. Furthermore, it is desirable to have M=0 so that the number of slots is minimized to reduce winding complexity and to maintain stator slot fill factors (fewer partially filled slots)—this is especially true when the number of slots is already large. The number of slots can be large if the number of phases is large, such as when PH=6 for a dual winding (wye or delta) commonly known to those skilled in the art. The number of slots can also be large when a design common to those skilled in the art is utilized wherein the number of slots equals two times the number of phases times the number of poles—in this case the invention art results in a stator having a number of slots greater than two times the number of phases times the number of poles.  
         [0037]     Altering the number of slots in a stator core from the conventional number brings with it certain difficulties regarding installation of windings in the stator. This is because the winding pattern will not begin and end in adjacent slots. For this reason, it is taught herein that particular slots are to be skipped in the winding process. Skipping slots roughly diametrically opposed from one another provides improved spatial balancing of applicable electromagnetic forces.  
         [0038]     Because of the skipped slots, industry standard type conductors are not used. Rather conductors having a unique pattern of endloops and slot segments are utilized. Due to the unique pattern of endloops, a hairpin type winding would require numerous shapes of hairpins and therefore, it is desirable, but not necessary, to form the conductor from one continuous conductor as can be seen in  FIG. 1 . Referring to  FIG. 1 , one embodiment of a conductor  10  is illustrated. This particular embodiment is configured for an 86 slot stator core. It will be appreciated that there are “normal” endloops  12  interconnected by slot segments  14  and two skip-endloops  16 . Although not shown in  FIG. 1 , the continuous conductor will be inserted into a stator core such that the slot segments  14  are disposed in the core slots. Skip-endloops  16  are intended to enable a slot segment  14  adjacent the skip-endloop  16  to be received in a slot different than the one in which it would have landed had the skip-endloop been a standard endloop. Stated another way, skip-endloops  16  position adjacent slot segments into slots that are farther away from one another than “normal” endloops  12 . The term adjacent slot segments, utilized herein, refers to two slot segments, which are attached to the same endloop. Such conductors allow for irregular slot counts to be wound without winding overlap issues. As noted, the  FIG. 1  embodiment of conductor  10  is intended for an 86-slot stator core to be operable with a 14 pole rotor and 6 phases. It will be appreciated that such a machine should bear  84  slots if full pitch or a multiple of six slots if fractional pitch. Typically, the number of “normal” endloops  12  greatly outnumbers the amount of skip-endloops  16 . This is true because the number of skip-endloops  16  is proportional to the number of additional slots ((M×PH)+N) over the standard number of slots (number of poles×number of phases) and as previously mentioned; it is desirable to minimize the number of slots. Therefore a conductor exhibits (from left to right) a series of at least two consecutive “normal” endloops  12  before having a skip-endloop  16 .  
         [0039]     While the specific conductor of  FIG. 1  is designated for use with an 86 slot stator core, it should be appreciated that machines with 14 poles and 6 phases are not limited to 86 slots to obtain the benefit of the invention. Rather, a 14 pole, 6 phase machine is to possess 85, 86, 87, 88, or 89 slots with M=0 or 91, 92, 93, 94, or 95 slots with M=1 and so forth. Any of these number of slots for a 14 pole, 6 phase machine will achieve the desired reduction in magnetic noise.  
         [0040]     Referring to  FIGS. 2A and 2B  and still using the 86 slot example, two winding passes are illustrated, one in each figure. Note that in each figure, there is included a broken line section. This section is intended to represent a duplication of the bending pattern of the conductor illustrated on the left side of the figure. In each case, the bend pattern illustrated is repeated three more times in the broken line section to complete one full length conductor (the same is true for the conductors shown in  FIGS. 7A and 7B , treated hereunder). For simplicity, the winding is also shown in  FIGS. 2A, 2B ,  7 A,  7 B and  11  to be in a linear state as if they were separated from the core and rolled out flat. Six phases are evidenced by the six conductors illustrated in each figure. The first pass P 1  ( FIG. 2A ), bears conductors having a form identical to that shown in  FIG. 1  hereof. The second pass P 2  ( FIG. 2B ) bears a slightly different configuration but which includes identical numerals. It is to be appreciated that the term “skip” is provided on the drawings with lead arrows to indicate where a stator slot exists but is not to be populated by a slot segment  14  during that particular pass. In the embodiment depicted in  FIGS. 2A and 2B , slot  43  and  86  are skipped in the first pass P 1  and slot  37  and  80  are skipped in the second pass P 2 . Additional winding passes will repeat the  FIG. 2A  and  FIG. 2B  patterns in alternating manner. The schematic view of this winding pattern of  FIGS. 2A and 2B  can be seen in  FIG. 3  after the completion of eight passes. Illustrated in  FIG. 3 , as a partial cross sectional representation of a stator core, is a configuration wound as in  FIG. 2A / 2 B and where slot  37  and  43  of the stator core are populated by only 4 slot segments each and therefore slots  37  and  43  (as well as slots  80  and  86  not shown in  FIG. 3 ) are populated by fewer slot segments than the rest of the slots, after eight passes.  
         [0041]     The resulting winding of  FIGS. 2A and 2B  conductors is further illustrated schematically in  FIG. 4  so that the step of each phase of conductors radially inwardly at the end of each pass can be visualized. It is to be understood that P 1 -P 8  are passes. Further, in order to make  FIGS. 10A and 10B  (discussed hereinafter) clear, each lead on each conductor (each conductor will have two leads) is labeled separately. For example, leads A 1  and A 7  extend from each end of a single conductor. Similarly, A 6  and A 12  extend from each end of a single conductor. The same is true for the leads marked with a B prefix. Referring to  FIG. 5 , and in conjunction with the above disclosure, it will be apparent how the leads and therefore the conductors are received into slots in the stator core.  
         [0042]     Relatedly,  FIG. 6  is a partial cross sectional view of an alternate wind pattern wherein the wind pattern of  FIG. 2A  is repeated twice followed by the wind pattern of  FIG. 2B  repeated twice, with this pattern repeated until the completion of eight passes. In this embodiment slot  37  and  43  have only 4 slot segments each and the slot segments are grouped in pairs within these slots. The desirability of this pattern is that the slot segments are disposed in the slots  37  and  43  in pairs such that the typical stator varnishing operation would bond the pairs together, creating a more rigid assembly of slot segments in less-populated slots  37  and  43 . As shown in the relative position on the drawing sheet of  FIGS. 2A and 2B , the second pass may be shifted from the first pass by PH slots, such that the conductors of a particular phase of the second pass are shifted from the conductors of the same phase of the first pass.  
         [0043]     In another alternate embodiment, referring to  FIG. 7A  (again having 86 slots), the first pass is similar to that illustrated in  FIG. 2A  except that the skip endloops  16  are positioned to cause the conductor to skip slot  37  and slot  80 . In the first pass P 1 , all conductors skip slots  37  and  80 . The illustration of  FIG. 7B  differs from that of  FIG. 7A .  FIG. 7B  presents a distinct second phase P 2  conductor from that of  FIG. 7A  in that the skip endloops  16  are positioned to cause it to populate slot  37  as opposed to slot  38  and slot  80  as opposed to slot  81 . In the second pass P 2 , all conductors skip slots  38  and  81 . In this embodiment, as in the  FIG. 2A / 2 B embodiment, first and second passes may alternate or two first passes and two second passes may alternate or any other similar alternating pattern. The desirability of this pattern is ease of manufacturing because only the first phase is disposed in different slots depending on the pass.  
         [0044]     Referring to  FIG. 8 , another embodiment is schematically illustrated wherein the winding pattern of FIGS.  7 A/ 7 B are employed where four spaced slot segments are illustrated in slots  37  and  38 , after eight passes.  
         [0045]     Referring to  FIG. 9  yet another alternate winding pattern is illustrated that uses a pattern that is the same for each pass. The pattern for example could be like that of  FIG. 7A . Such arrangements will leave two slots, as for example  37  and  80 , empty. The desirability of this pattern is ease of manufacturing because all of the conductors of each phase have the same shape (the conductors are the same except shifted one slot from another).  
         [0046]     To ensure clarity in the understanding of the disclosure herein by one less familiar with alternators, reference is made to  FIG. 10  wherein a schematic cross-section view of a prior art alternator is illustrated. The alternator  100  includes a pulley  102  connected to a rotor shaft  104  upon which a pair of pole pieces  106  and  108  are rotationally supported. Pole pieces  106 ,  108  are configured to present a plurality of pole fingers  110 ,  112  (two visible) circumferentially around the shaft  104 . Rotor core windings  114  are positioned between fingers  110 / 112 . The alternator  100  further includes a stator core  116  having a number of slots, the number being of full or fractional pitch, as explained above (not shown) and stator core windings  118  therein. The noted alternator components are supported in position by a front end frame  120  and a rear end frame  122 . Portions of the rotor and associated rotating poles create an induced current in the stator core windings, which current is usable as generated electrical energy.  
         [0047]     Referring to  FIG. 11 , a cascade style winding pattern is illustrated. While the illustrated style is itself known in the art, it is not know in combination with the stator core slot configuration taught herein.  
         [0048]     In view of the unconventionality of the foregoing teaching regarding the configuration and windings of a stator core, it is prudent to include schematic wiring diagrams to ensure complete understanding by a reader. With reference to  FIGS. 12A and 12B , a dual wye and a 3-phase distributed wye diagram are illustrated. In  FIG. 12A , each leg of the wye is connected in parallel, for example, A 2  and B 2  are connected to each other and also to a diode pair  130  as shown. Connections are likewise for each other pair of diode end leads of each conductor. In addition, each leg of the wye is connected at the neutral point  132  or  134  respectively. As can be seen in  FIG. 12A , one wye winding is shifted by approximately 30 degrees with respect to the other wye winding. Returning to  FIG. 12B , the 3-phase wye uses a single neutral point  136  and only three diode pairs  138 . Additional conductor lead connections are connected in parallel at each node  140 ,  142  and  144  as illustrated. As can be seen in  FIG. 12B , each phase is comprised of two portions wherein one portion is shifted approximately 30 degrees from the other portion.