Abstract:
A motor having a seal assembly includes a motor housing having a rotatable shaft disposed therein. Also included is a first seal operably coupled to the rotatable shaft and having an engagement portion, wherein the first seal is configured to rotate in conjunction with the rotatable shaft. Further included is a second seal disposed in the motor housing and having a guiding portion, wherein the engagement portion of the first seal guidably rotates within the guiding portion of the second seal forming at least one labyrinth seal, and wherein at least one of the first seal and the second seal comprise an insulated material.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to motors, and more particularly to seal assemblies therein. 
         [0002]    Seal assemblies associated with motors are typically employed for a high degree of ingress protection of motor components, such as bearings, from dust and water, for example. One such seal assembly is a labyrinth seal assembly and often includes two components, a rotating portion and a static, or stationary, portion, both of which are typically made of a metal, such as steel or bronze. The rotating part may be fit on a shaft and engaged with the static portion. In particular applications, such as variable frequency drive (VFD) applications, the motor is subjected to shaft currents. The shaft currents result in undesirable effects associated with the bearings, seals, and potentially other motor components. In the case of labyrinth seals, the rotating part rotates relative to the static part in operation. In a case where these parts are made of steel, there is a relatively small gap between the parts. In some cases, metal to metal contact between the static and rotating parts may occur, with shaft currents due to the VFD drives causing undesirable effects. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    According to one aspect of the invention, a motor having a seal assembly includes a motor housing having a rotatable shaft disposed therein. Also included is a first seal operably coupled to the rotatable shaft and having an engagement portion, wherein the first seal is configured to rotate in conjunction with the rotatable shaft. Further included is a second seal disposed in the motor housing and having a guiding portion, wherein the engagement portion of the first seal guidably rotates within the guiding portion of the second seal forming at least one labyrinth seal, and wherein at least one of the first seal and the second seal is includes an insulated material. 
         [0004]    According to another aspect of the invention, a motor having a seal assembly includes a rotatable shaft. Also included is a first seal operably coupled to the rotatable shaft and having an engagement portion. Further included is a second seal having a guiding portion, wherein the engagement portion of the first seal guidably rotates within the guiding portion of the second seal, and wherein at least one of the first seal and the second seal is insulated with an insulating substance. 
         [0005]    According to yet another aspect of the invention, a motor having a seal assembly includes a motor housing having a rotatable shaft disposed therein. Also included is a first seal operably coupled to the rotatable shaft and having an engagement portion, wherein the first seal is configured to rotate in conjunction with the rotatable shaft. Further included is a second seal that is relatively static and in operable connection with an end shield, wherein the second seal includes a guiding portion, wherein the engagement portion of the first seal guidably rotates within the guiding portion of the second seal, and wherein the second seal is insulated with an insulating substance. 
         [0006]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0007]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  is a top, cross-sectional view of a motor having a drive end side and an opposite drive end side; 
           [0009]      FIG. 2  is a perspective view of at least one seal assembly located proximate the drive end side of the motor; and 
           [0010]      FIG. 3  is a perspective view of at least one seal assembly located proximate the opposite drive end side of the motor. 
       
    
    
       [0011]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring to  FIG. 1 , an induction motor is generally referred to with the numeral  10 . The induction motor  10  employed for the invention may be a single-phase or polyphase induction motor, and furthermore may be used in constant-speed applications or variable frequency drive (VFD) applications. More specifically, the induction motor  10  may be used in mining applications, for example. 
         [0013]    The induction motor  10  includes power being supplied to a rotor, or a shaft  12 , by means of electromagnetic induction via a stator core assembly  14 . The shaft  12  extends within a rotor core assembly  16  and longitudinally from proximate a drive end (DE) side  20  of the induction motor  10  to an opposite drive end (ODE) side  22  of the induction motor. The induction motor  10  includes a motor housing  18  that operably supports and/or houses various components. Both the DE side  20  and the ODE side  22  include a number of similar components, such as an end shield  24 , a bearing cap  26  and at least one bearing  28 . Also included at both the DE side  20  and the ODE side  22  is at least one seal assembly for providing ingress protection of components of the induction motor  10 , such as the at least one bearing  28 . The ingress protection relates to the prevention of debris and particulate matter, such as dust, water, etc., from entering certain portions of the induction motor  10 . 
         [0014]    Referring now to  FIG. 2 , an enlarged, cross-sectional view of the DE side  20  of the induction motor  10  is illustrated. Included is an inner seal assembly  30  that is in operable connection with one or more components of the DE side  20 , such as the bearing cap  26 , for example. The inner seal assembly  30  includes a first seal component  32  and a second seal component  34 . The first seal component  32  is rotatable and configured to be fit on the shaft  12  along a shaft outer diameter  36  and a first seal inner diameter  38 . The first seal component  32  rotates with the shaft  12  and is disposed in close proximity, or in contact with, the at least one bearing  28 . The first seal component  32  includes an engagement portion  40  that is of the form of a protrusion extending in an axial direction of the shaft  12  and circumferentially around the shaft  12 . The first seal component  32  may be formed of numerous materials and will vary depending on the particular application of use. Common materials for the first seal component  32  include various metals including, but not limited to, steel and bronze. 
         [0015]    The second seal component  34  of the inner seal assembly  30  is relatively static, or stationary, with respect to the first seal component  32 , and includes a guiding portion  42  that is configured to fittingly receive the engagement portion  40  of the first seal component  32 . In the illustrated embodiment, the guiding portion  42  is a recess that receives the engagement portion  40 , but it is to be appreciated that numerous other geometric configurations may be employed to achieve a basic labyrinth function. The second seal component  34  may be formed of various insulating materials, with one such insulating material being epoxy glass cloth laminated sheet, for example. It is to be appreciated that various alternative insulating materials may be employed, provided the insulating material sufficiently insulates the seals from each other and from shaft currents that are commonly generated from the shaft  12  in VFD applications. 
         [0016]    The DE side  20  of the induction motor  10  also includes an outer seal assembly  44  that is in operable connection with one or more components of the DE side  20 , such as the shaft  12  and the end shield  24 , for example. The outer seal assembly  44  includes a third seal component  46  and a fourth seal component  48 . The third seal component  46  is rotatable and configured to be fit on the shaft  12  along the shaft outer diameter  36  and a third seal inner diameter  50 . The third seal component  46  rotates with the shaft  12  at a rotational velocity equal to or less than that of the rotational velocity of the shaft  12  and is disposed in close proximity, or in contact with, the at least one bearing  28 . The third seal component  46  includes an engagement portion  52  similar to that of the engagement portion  40  of the first seal component  32 . Similar to the first seal component  32 , the third seal component  46  may be formed of numerous materials and will vary depending on the particular application of use. Common materials for the third seal component  46  include various metals including, but not limited to, steel and bronze. 
         [0017]    The fourth seal component  48  of the outer seal assembly  44  is relatively static, or stationary, with respect to the third seal component  46 , and includes a guiding portion  54  similar to that of the guiding portion  42  of the second seal component  34 . The fourth seal component  48  may be formed of various insulating materials, with one such insulating material being epoxy glass cloth laminated sheet, for example. It is to be appreciated that various alternative insulating materials may be employed, provided the insulating material sufficiently insulates the seals from shaft currents that are commonly generated from the shaft  12  in VFD applications. 
         [0018]    Referring now to  FIG. 3 , an enlarged, cross-sectional view of the ODE side  22  of the induction motor  10  is illustrated. As apparent from reference to the DE side  20  ( FIG. 2 ), the ODE side  22  comprises similar components as that of the previously described DE side  20 , yet simply arranged in a mirrored configuration. For simplicity of discussion, similar components will be referred to with common terminology and reference numerals. Included at the ODE side  22  is a ground brush  56 , but it is to be appreciated that the induction motor  10  may be of a brushless variety. The ODE side  22  includes the inner seal assembly  30  and the outer seal assembly  44  that are similar in construction and arrangement as that of the DE side  20 . 
         [0019]    The foregoing description refers to the second seal component  34  and the fourth seal component  48  as being made of an insulated material, such as epoxy glass cloth laminated sheet, but it is to be understood that the first seal component  32  or the third seal component  46  may be formed of the insulated material. This may be independent of, or in combination with, the second seal component  34  and fourth seal component  48 . 
         [0020]    Alternatively, rather than at least one of the seal components  32 ,  34 ,  46  or  48  being made of an insulating material, the inner seal assembly  30  and/or the outer seal assembly  44  may be merely insulated. Various embodiments include sealing at least one of the seal components  32 ,  34 ,  46  or  48  with an insulating substance, such as a resin or a coating. Additionally, an insulating paper may be disposed proximate at least one of the seal components  32  or  46  with the shaft  28 , or with seal components  34  or  48  with the enclosure. 
         [0021]    Advantageously, the inner seal assembly  30  and/or the outer seal assembly  44  provide a high degree of ingress protection from debris and undesirable substances, as well as a resistance against shaft currents that may otherwise pass to components of the induction motor  10 . 
         [0022]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.