Abstract:
An arc resistant terminal block has a terminal post insulator and a terminal lead strap that increase the strike and creep distance of electrically charged components to grounded components by non-conductive terminal block and insulators.

Description:
BACKGROUND 
       [0001]    The present application is directed to a generator or a generator/motor including a terminal block, and more specifically to an arc resistant terminal block design. 
         [0002]    Oil cooled electric generators include connection terminals that connect the generator to an external electrical system, thereby allowing the generator to act as a power source for the electric system. The connection terminals include conductive and non-conductive sealing components that prevent oil within the generator from leaking out of the generator, while still allowing the conductive electrical connections to protrude from the generator to provide electrical power. 
         [0003]    In normal conditions at altitude or adverse conditions, such as an over-voltage, the generator terminals can undergo an arc-fault during which electricity can arc over a strike distance (pass through the air between two non-contacting conducting components) or a creep distance (pass over non-conducting components connecting two conducting components). Arc events occur when the voltage of the terminals exceeds an amount accounted for in the minimum strike and creep distances of the electric terminal. Further influencing arc events are the atmospheric pressure, cleanliness of surfaces and the ambient conditions. For this reason components, such as terminals, which are used in external or exposed positions can have longer minimum strike and creep distance requirements than terminals used within a controlled environment. 
       SUMMARY 
       [0004]    Disclosed is a generator and/or generator/motor having a terminal connection assembly with a terminal lead insulator received in a terminal block slot, a terminal post extending through the insulator and the terminal block slot, a terminal lead strap electrically contacting the terminal post, and a threaded terminal electrically contacting the terminal lead strap. 
         [0005]    Also disclosed is a terminal lead assembly having a terminal post with an exterior end and a terminal lead strap contacting said exterior end. The terminal lead strap has a pair of angled edges. 
         [0006]    Also disclosed is a terminal lead insulator having a ring with a plurality of protrusions extending radially outward from the ring. The ring also has a first extension section extending axially from the ring beyond the plurality of protrusions in a first direction and a second section extending axially from the ring beyond the plurality of protrusions in a second direction. 
         [0007]    Also disclosed is a terminal block having a plurality of terminal lead slots, wherein each of the terminal lead slots has a recessed section for receiving a terminal lead insulator extension and an open section for receiving terminal leads. 
         [0008]    Also disclosed is a method for assembling an arc resistant terminal block having the steps of inserting a terminal lead post into an insulator ring, inserting the insulator ring into a generator, fitting a terminal block about the terminal lead posts and the insulator ring, and installing a terminal lead strap contacting the terminal lead post. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0010]      FIG. 1  schematically illustrates an example generator and/or generator/motor having an external facing terminal. 
           [0011]      FIG. 2  illustrates an example terminal connection assembly. 
           [0012]      FIG. 3  illustrates a terminal lead assembly for use in the example terminal connection assembly of  FIG. 2 . 
           [0013]      FIG. 4A  illustrates the terminal lead strap of  FIG. 3  isolated from the terminal lead assembly. 
           [0014]      FIG. 4B  illustrates the terminal lead strap of  FIG. 3  isolated from the terminal lead assembly in a front view. 
           [0015]      FIG. 5A  illustrates a side view of a terminal lead insulator for use in an example terminal connection assembly. 
           [0016]      FIG. 5B  illustrates a top view of a terminal lead insulator for use in an example terminal connection assembly. 
           [0017]      FIG. 6A  illustrates a bottom view of a terminal block for use in an example terminal connection assembly. 
           [0018]      FIG. 6B  illustrates a top view of the terminal block of  FIG. 6A . 
           [0019]      FIG. 7  illustrates a sectional view of an example terminal connection assembly. 
           [0020]      FIG. 8  illustrates an isometric view of an example terminal connection assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Illustrated in  FIG. 1  is a schematic drawing of a generator and/or generator/motor assembly  10 . The generator assembly  10  includes a terminal connection assembly  20 . The terminal connection assembly  20  has multiple terminal connections  30  for connecting the generator assembly  10  to an electrical system. Each of the terminal connections  30  are connected to a generator winding  40  via a terminal to winding connection  50 . 
         [0022]      FIG. 2  illustrates a more detailed terminal connection assembly  100  (corresponding to the terminal connection assembly  20  of  FIG. 1 ). The terminal connection assembly  100  includes a terminal block  110  that is fastened to a generator housing  150  using multiple fasteners  114 . Additionally, the terminal block  110  includes a plurality of terminal block isolation ridges  160  that separate each of multiple threaded terminal  140 . Passing through the terminal block  110  are a plurality of terminal lead assemblies  120 . Each of the terminal lead assemblies  120  has a terminal post  124  that connects the terminal to winding connection  50  (illustrated in  FIG. 1 ) to a terminal lead strap  122 . In the illustrated example of  FIG. 2 , a square washer  126  is used to hold the terminal lead assembly  120  in place. The threaded terminal  140  provides a post for connecting the terminal lead assembly  120  to the electric system. 
         [0023]    The terminal lead assembly  120  is further held in place, and isolated from the generator housing  150 , using a terminal lead insulator  130 . The terminal lead insulator  130  fits into a terminal post slot  112  in the terminal block  110 . The terminal lead insulator  130  increases both the minimum creep distance and the minimum strike distance of the terminal connection assembly  100  through the use of a terminal lead insulator extension, as described below. 
         [0024]    An example terminal lead assembly  200  is illustrated in  FIG. 3 . The terminal lead assembly  200  has a terminal lead strap  222  and a terminal post  224 . The terminal post  224  includes an upper terminal post seal protrusion  228  and a lower terminal post seal protrusion  229  that extend radially outward from the terminal post  224 . When the terminal lead assembly  200  is installed in the generator body, an o-ring (illustrated in  FIG. 7 ) is located between the upper and lower seal protrusions  228 ,  229  thereby preventing oil inside the generator from leaking out between the terminal post  224  and the terminal lead insulator  330 . When installed, each of the seal protrusions  228 ,  229  is within the terminal lead insulator  330  (illustrated in  FIGS. 5A and 5B ). 
         [0025]      FIGS. 4A and 4B  illustrate an example terminal lead strap  222 , in a side view ( FIG. 4A ) and a front view ( FIG. 4B ). The terminal lead strap  222  includes an exterior end  230  and a folded end  260 . The exterior end  230  contacts the threaded terminal  140  (illustrated in  FIG. 2 ). The folded end  260  contacts the terminal post  224  at a contact edge  254  (illustrated in  FIG. 3 ). The terminal lead strap  222  and the terminal post  224  can be brazed together such that the terminal lead assembly is an inseparable assembly. In this way, a conductive path between the terminal post  224  and the threaded terminal  140  is maintained. The corners of the folded end  260  of the terminal lead strap  222  are angled with a pair of angled edges  252 . The angled edges  252  get closer together progressively along a length  240  of the folded end  260 , thereby increasing the strike distance by eliminating the corners of the folded end  260 . 
         [0026]      FIGS. 5A and 5B  illustrate the terminal lead insulator  330  isolated from the terminal connection assembly  100  of  FIG. 2 .  FIG. 5A  illustrates a side view, and  FIG. 5B  illustrates a top view. The terminal lead insulator  330  is a ring of non-conductive material, and has an upper seal protrusion  338 , a lower seal protrusion  339 , and a through hole  340 . The terminal lead insulator  330  further includes an upper insulator extension  310  that fits into an insulator extension slot  416  (illustrated in  FIG. 6A ) in the terminal block  110 . The upper insulator extension  310  increases the creep distance and the strike distance of the terminal connection assembly  100  as is described below with regards to  FIG. 7 . A lower body portion  320  is also included as part of the terminal lead insulator  330 . The lower body portion  320  has a larger radial thickness than the upper insulator extension  310 . 
         [0027]    As with the terminal lead assembly  200 , an o-ring is located between the seal protrusions  338 ,  339  when the terminal lead insulator  330  is installed, thereby fully sealing the terminal post and the terminal lead insulator  330  in the generator body. While the above descriptions include an o-ring seal design, it is understood that alternate seal designs could be used in place of an o-ring style seal and maintain the effectiveness of the present disclosure. 
         [0028]      FIGS. 6A and 6B  illustrate a terminal block  400  in an underside view ( FIG. 6A ) and a top view ( FIG. 6B ). The terminal block  400  includes a set of terminal post slots  412  and recessed terminal extension slots  416 . The upper insulator extension  310  of the terminal lead insulator  330  fits within the terminal block  400  in the recessed terminal extension slot  416  and the terminal post  224  extends through the terminal post slot  412 . The terminal block  400  further includes multiple fastener holes  414  for fastening the terminal block  400  to the generator housing. 
         [0029]    The terminal block  400  includes isolation ridges  418  between each of the terminal post slots  412  and their adjacent terminal post slots  412 . The terminal isolation ridges  418  allow for a cap to be fitted to the terminal connection after the generator is connected to an electric system, thereby protecting the terminal connection assembly  100 . The terminal isolation ridges  418  further increase the distance of strike and creep zones that can be created as a result of a buildup of grime or other materials by providing an insulative barrier between the connection terminals. 
         [0030]    A cross-sectional view of a connection assembly  500  is illustrated in  FIG. 7  and shows a terminal lead assembly installed in the terminal connection assembly  500 . Also illustrated in  FIG. 7  are the terminal lead insulator  530  and a terminal block  540 . The terminal block  540  can be the terminal block  400  illustrated in  FIGS. 6A and 6B . The terminal lead insulator  530  and the terminal post  560  are sealed to the generator housing a pair of o-rings  570 . The o-rings  570  are a conventional design and prevent oil leakage because the o-ring elastomer creates the seal based on the inner and outer diameters of the rigid surfaces. The upper and lower protrusions of the terminal post  560  and the terminal lead insulator  530  prevent the o-rings  570  from sliding up or down, thereby maintaining the seal. The minimum strike distance  510  and the minimum creep distance  520  of the terminal connection assembly are also illustrated. Also shown connected to the terminal post  560  is a terminal lead strap  550 . 
         [0031]    The upper insulator extension  580  increases the creep distance  520  of the terminal assembly by increasing the length of the surface over which electrical charge must creep before an arc event can occur. Likewise the upper insulator extension  580  increases the strike distance  510  by placing an isolative barrier in the shortest distance between the conducting post  560  and the conductive generator housing. Increasing the creep distance  520  and the strike distance  510  reduces the risk of arc events within the connection assembly  500 . 
         [0032]      FIG. 8  illustrates a partial isometric view of the terminal connection assembly  600  connected to a generator body  670 , including the terminal lead strap  620 . The terminal lead strap  620  is brazed to contact edge  616 , which provides the electrical contact between the terminal lead strap  620  and the terminal post  613 . An additional feature of the terminal strap  620  is the angled edge  614 . As described with regards to  FIGS. 4A and 4B , the angled edge  614  increase the strike distance  650  between the lead strap and the terminal block  640 . The increased distance prevents an arc from jumping the gap between the lead strap and terminal block. Although  FIG. 8  illustrates the angled edge  614  as a straight edge it is understood that a curved edge or multiple angled edges could also increase minimum strike distance, rather than the illustrated straight edge  614 . 
         [0033]    Furthermore, as described with regards to  FIG. 2 , the terminal lead strap  620  is held in place between the terminal block isolation ridges  660  by a square washer  626 , and the terminal post  613  is held in place via a terminal lead insulator  630 . The terminal lead insulator  630  includes an insulator extension, which is received in a terminal extension slot defined by a first surface  622  and a second surface  624 . 
         [0034]    In order to construct the above described terminal connection assembly  100 , the described components are combined into a single assembly. First, the terminal post  124  receives an o-ring between the seal protrusions  228 ,  229  and is inserted into the center of the terminal lead insulator ring  130 . Then the terminal lead insulator ring  130  receives an o-ring between the terminal lead insulator protrusions  338 ,  339  and is inserted into a terminal lead hole in the generator. Next, the terminal block  110  is fitted about the terminal lead insulator ring extensions  310  such that each of the extensions  310  fits in a recessed terminal lead insulator ring extension slot  416  and each of the terminal lead posts  124  extends through an open terminal post slot  412 . 
         [0035]    Next, the terminal block  110  is fastened to the generator housing fasteners  114  and a terminal lead strap  122  is connected to each terminal lead post  124 . In an alternate example, the terminal lead strap  122  and the terminal post  124  are brazed together prior to the step of inserting the terminal post  124  into the terminal lead insulator ring  130 . The terminal lead strap  122 , and by extension, the terminal post  124 , is held in place with a square washer  126 . Once assembled, the threaded terminal nut  165  can be connected to the terminal lead straps  122  in a known fashion, thereby allowing the generator to be connected to an external electrical system. 
         [0036]    Although an example has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.