Abstract:
A method for facilitating damping torsional or ring vibrations of a dynamoelectric machine including a rotor assembly with a first amortisseur bar and a second amortisseur bar extending therefrom and terminating at an endring is provided. The method includes providing a damping assembly, and positioning the damping between the first amortisseur bar and the second amortisseur bar such that the damping assembly contacts the first and second amortisseur bars, and is substantially proximate the endring or alternatively the damping assembly is positioned only over one amortisseur bar.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to dynamoelectric machines and more particularly to damping amortisseur bar vibration.  
           [0002]    Dynamoelectric machines are utilized in many manufacturing applications. Failure of key components within a dynamoelectric machine, such as amortisseur bars, can cause lost production time, injury to personnel, and loss of capital equipment, all of which can reduce profitability. One known cause of dynamoelectric machine failure is motor airgap torque pulsations. When the frequency of these pulsations equal the torsional or ring natural frequency of the amortisseur bars, resonance occurs. In that case the vibratory stresses in the amortisseur bars may exceed a fatigue endurance limit and an amortisseur bar fatigue failure may occur. Subsequently the broken amortisseur bar may bend radially outwards under the action of centrifugal forces and contacts a stator winding end head with harmful consequences.  
           [0003]    A factor in these failures is the fact that the inherent damping characteristic of amortisseur bars is low. As a consequence when resonance occurs, very small torque pulsations will result in a significant vibratory response, if, and when, the pulsation frequency equals the torsional natural frequency of the amortisseur bars.  
         SUMMARY OF THE INVENTION  
         [0004]    In one aspect, a method for facilitating damping torsional vibrations of a dynamoelectric machine including a rotor assembly with a first amortisseur bar and a second amortisseur bar extending therefrom and terminating at an endring is provided. The method includes providing a damping assembly, and positioning the damping assembly between the first amortisseur bar and the second amortisseur bar such that the damping assembly contacts the first and second amortisseur bars, and is substantially proximate the endring.  
           [0005]    In another aspect, an amortisseur bar damping device includes a rigid support member including a first side and a second side opposite the first side, and a first resilient member disposed to the first side and a second resilient member disposed to the second side.  
           [0006]    In another aspect, a damping assembly includes a rotor core, a first amortisseur bar, and a second amortisseur bar. Both the first and second amortisseur bars extend from the core and the second amortisseur bar is substantially parallel to the first amortisseur bar. The damping assembly also includes a damping device contacting the first and second amortisseur bars distal from the rotor core and substantially proximate an endring. The damping device also includes a rigid support member including a first side and a second side opposite the first side, and a first resilient member disposed to the first side and a second resilient member disposed to the second side.  
           [0007]    In another aspect, a motor includes a housing and a stator including a bore therethrough is mounted in the housing. The motor also includes a rotor shaft extending at least partially through the bore. A rotor assembly is mounted on the rotor shaft. The rotor assembly includes a rotor core mounted to the rotor shaft, and a plurality of amortisseur bars extending axially through and projecting from at least one end of the rotor core. It also includes a plurality of endrings connected to each end of the amortisseur bars distal from the core. The rotor assembly also includes an endplate attached to the core, and an amortisseur bar damping device mounted between at least two of the amortisseur bars, the amortisseur bar damping device distal the core and substantially proximate endring.  
           [0008]    In another aspect, an amortisseur bar damping device includes a rigid support member including a first side and a second side opposite the first side. A U shaped channel is disposed longitudinally along the first side. The damping device also includes a resilient member disposed to the U shaped channel. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective view of a known rotor assembly.  
         [0010]    [0010]FIG. 2 is a perspective view of an amortisseur bar damping device.  
         [0011]    [0011]FIG. 3 is a partial end view of a rotor taken in the direction of section line II II in FIG. 1 including the amortisseur bar damping device shown in FIG. 2.  
         [0012]    [0012]FIG. 4 is a partial cross section of a rotor assembly taken along section line III III in FIG. 3 including the amortisseur bar damping device shown in FIG. 2.  
         [0013]    [0013]FIG. 5 is an axial view an amortisseur bar damping device shown in FIG. 2.  
         [0014]    [0014]FIG. 6 is a cross section of a motor.  
         [0015]    [0015]FIG. 7 is a perspective view of a different embodiment of an amortisseur bar damping device.  
         [0016]    [0016]FIG. 8 is a plan view of the amortisseur bar damping device shown in FIG. 7. 
     
    
     DETAILED DESCRIPTION  
       [0017]    [0017]FIG. 1 is a perspective view of a known rotor assembly  10 . Rotor assembly  10  includes a plurality of rotor core sections  14  disposed about a shaft  12 . Each rotor core section  14  includes a plurality of amortisseur bars  16  passing axially therethrough and extending a substantial distance beyond rotor core section″s  14  ends. Amortisseur bars  16  extend over an endplate (not shown in FIG. 1) that is rigidly disposed to rotor core  14 . Amortisseur bars  16  terminate at a plurality of endrings  18 . Although five amortisseur bars are shown in each rotor core section  14 , more or less amortisseur bars  16  may be employed.  
         [0018]    [0018]FIG. 2 is a perspective view of an amortisseur bar damping device  20  including a first member  22 , a second member  24 , and a third member  26  disposed between first member  22  and second member  24 . First and second members  22  and  24  each include a width  28 , a height  32 , a thickness  34 , and a side  44 . Thickness  34  is substantially constant. First member  22  and second member  24  comprise a resilient material and substantially rectangular width  28  substantially greater than thickness  34 . In one embodiment, first and second members  22  and  24  are manufactured from vulcanized natural rubber. Alternatively, first and second members  22  and  24  are manufactured from a synthetic elastomer such as neoprene.  
         [0019]    Third member  26  includes a first side  38  and a second side  40  opposite first side  38 . First member side  44  is disposed to first side  38  of third member  26 , and second member side  44  is disposed to second side  40  of third member  26 . In one embodiment, first member side  44  is bonded to first side  38  of third member  26 , and second member side  44  is bonded to second side  40  of third member  26 . Third member  26  includes a width  28 , a height  32 , and a thickness  36 . Thickness  36  is substantially constant. Third member  26  is machined from a rigid material and substantially cubicle having width  28 , height  32 , and thickness  36  substantially equal. In another embodiment, third member  26  is rectangular having width  28  substantially greater than height  32 . In one embodiment, third member  26  is machined from stainless steel. Alternatively, third member  26  is machined from titanium.  
         [0020]    Amortisseur bar damping device  20  is utilized to facilitate a reduction of torsional vibrations in dynamoelectric machines. It is contemplated that the benefits of amortisseur bar damping devices  20  accrue to all rotor assemblies and motors having amortisseur bars. In one embodiment, amortisseur bar damping device  20  is utilized to facilitate a reduction of torsional vibrations in motors for refiner drives on a sinusoidal power supply.  
         [0021]    [0021]FIG. 3 is a partial end view of rotor  10  taken in the direction of section line II II in FIG. 1 including an amortisseur bar damping device  20  shown in FIG. 2. FIG. 4 is a partial cross section of rotor  10  taken along section line III III in FIG. 3 including amortisseur bar damping device  20  shown in FIG. 2. Amortisseur bars  16  extend past an endplate  56  that is rigidly disposed on rotor core  14 . Amortisseur bars  16  terminate at endring  18 . Amortisseur bars  16  include amortisseur bars  46 ,  48 ,  50 ,  52 , and  54 . In an exemplary embodiment, a first amortisseur bar damping device  20  is disposed between amortisseur bar  46  and amortisseur bar  48 , and a second amortisseur bar damping device  20  is disposed between amortisseur bar  52  and amortisseur bar  54 . First and second amortisseur bar damping devices  20  are positioned substantially proximate to endring  18 .  
         [0022]    In one embodiment, amortisseur bar  46 , amortisseur bar  48 , and amortisseur bar  50  are adjacent such that amortisseur bar damping device  20  is disposed between first amortisseur bar  46  and second amortisseur bar  48 , and a second amortisseur bar damping device  20  is disposed between amortisseur bar  48  and third amortisseur bar  50 . First and second amortisseur bar damping devices  20  are positioned substantially proximate to endring  18 .  
         [0023]    [0023]FIG. 5 is an axial view of amortisseur bar damping device  20  shown in FIG. 2. In an exemplary embodiment, amortisseur bar damping device  20  is mounted to endplate  56  and disposed between amortisseur bar  46  and amortisseur bar  48  with a fastener  58 .  
         [0024]    In another embodiment, amortisseur bar damping device  20  may be disposed between at least two or more amortisseur bars  16  by at least one of a weld, a fastener, and a locking plate. In an additional embodiment, amortisseur bar damping device  20  may be disposed between at least two or more amortisseur bars  16  by welding support member  26  to endplate  56  and bonding first and second resilient members  22  and  24  to support member  26  afterwards.  
         [0025]    [0025]FIG. 6 is a cross sectional view of a motor  60  including a housing  62  and a stator  64  having a bore  66  therethrough. Stator  64  is mounted in housing  62 .  
         [0026]    Rotor shaft  12  extends at least partially through bore  66  and rotor assembly  10  is mounted to rotor shaft  12 . Rotor assembly  10  includes a rotor core  14  mounted on rotor shaft  12 . Rotor assembly  10  also includes a plurality of amortisseur bars  16  extending axially through and projecting from at least one end of the rotor core  14 . A plurality of endrings  18  connecting to amortisseur bars  16  distal from the rotor core  14  and an endplate  56 . Rotor assembly  10  additionally includes amortisseur bar damping device  20  (shown in FIG. 2) mounted between at least two amortisseur bars  16  and distal from rotor core  14  and substantially proximate endrings  18 .  
         [0027]    [0027]FIG. 7 is a perspective view and FIG. 8 is a plan view of another embodiment of an amortisseur bar damping device  70  including a support member  72  and a resilient member  80  disposed to support member  72 . Support member  72  includes a height  74 , a length  76 , and a thickness  78 . In one embodiment, support member  72  is machined from a rigid material, and is substantially rectangular. Height  74  is about 0.900 inches, length  76  is about 5.000 inches and thickness  78  is about 2.000 inches. In one embodiment, support member  72  is machined from a metallic material such as stainless steel. Alternatively, support member  72  is manufactured from a non-metallic material such as a glass laminate, a plastic, and a composite.  
         [0028]    Resilient member  80  includes a length (not shown in FIG. 7), a width (not shown in FIG. 7), a thickness  86 , and a side  88 . Thickness  86  is substantially constant. Resilient member  80  is substantially rectangular having the length substantially greater than the width. In one embodiment, resilient member″s  80  length is substantially equal to length  76 . In another embodiment, resilient member″s  80  length is substantially less than or greater than length  76 . In one embodiment, resilient member  80  is manufactured from an elastomer such as natural rubber, butyl, and neoprene.  
         [0029]    Rigid support member  72  includes a first side  90 , a second side  92  opposite first side  90 , and a U shaped channel  100 . Channel  100  is disposed longitudinally along first side  90 . Resilient member side  88  is disposed to channel  100 . In one embodiment, resilient member side  88  is bonded to channel  100 . In an exemplary embodiment, amortisseur bar damping device  70  is mounted to endplate  56  and disposed on amortisseur bar  16  by a plurality of locking plates  102  and fasteners  104 . Amortisseur bar damping device  70  is positioned substantially proximate to endring  18 .  
         [0030]    In an alternate embodiment, U shaped channel  100  is a rectangular channel. Additionally, channel  100  can be a shape other than rectangular shaped and U shaped, such as a shape with at least one line of symmetry and a shape with no lines of symmetry.  
         [0031]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.