Method of sealing a generator stator bar and a stator bar end fitting

Abstract

A method of sealing a generator stator bar and a stator bar end fitting receiving the end including the steps of: brazing the fitting to the end of the stator bar with a braze material; applying a metallic barrier coating material to the end of the stator bar in the fitting; heating the fitting at a temperature at least as hot as a liquidus temperature of the metallic coating material and cooler than a solidus temperature of the braze material; coating the end of the stator bar in the fitting with liquid metallic barrier coating material, and solidifying the liquefied metallic coating material to form a metallic barrier coating on the end of the stator bar in the fitting.

1 . A method of sealing a generator stator bar and a stator bar end fitting receiving the end comprising:
 attaching the fitting to the end of the stator bar with a braze material;   applying a metallic barrier coating material to the end of the stator bar attached to the fitting;   heating the fitting at a temperature at least as hot as a liquidus temperature of the metallic coating material and cooler than a solidus temperature of the braze material to liquefy the metallic coating material;   coating the end of the stator bar in the fitting with the liquid metallic barrier coating material, and   cooling the fitting to solidify the liquefied metallic coating material to form a metallic barrier coating on the end of the stator bar in the fitting.   
   
   
       2 . The method as in  claim 1  wherein the end of the stator bar is horizontal as the liquid metallic barrier coating coats the end of the stator bar. 
   
   
       3 . The method as in  claim 1  wherein attaching the fitting comprises brazing the fitting and stator bar with the braze material that includes a phosphorous copper braze alloy, and the metallic coating material comprises a tin-silver-copper alloy. 
   
   
       4 . The method as in  claim 3  wherein brazing the fitting comprises brazing with at least one of a BCuP-5 and a BCuP-1 phosphorous copper braze alloy, and the metallic coating comprises a Sn/3.8Ag/0.7Cu solder material. 
   
   
       5 . The method as in  claim 3  wherein the fitting is brazed with the braze alloy having a solidus temperature of no cooler than 600 degrees Celsius and the metallic coating material has a liquidus temperature no hotter than 600 degrees Celsius. 
   
   
       6 . The method as in  claim 1  wherein the fitting is oriented vertically during the step of coating the end of the stator bar with liquid metallic coating material. 
   
   
       7 . The method as in  claim 1  wherein the end of the stator bar comprises ends of hollow strands extending beyond ends of solid strands of the bar, and the liquid metallic coating covers the ends of the solid strands and said ends of the hollow strands extends above the liquid metallic coating. 
   
   
       8 . The method as in  claim 1  wherein the end of the stator bar comprises ends of hollow strands, and the method further comprises inserting hollow inserts into open ends of the hollow strands such that the inserts extend beyond ends of solid strands of the bar, and the liquid metallic coating covers the ends of the solid strands and flows around the hollow inserts. 
   
   
       9 . The method as in  claim 8  wherein the inserts are ceramic. 
   
   
       10 . The method as in  claim 1  wherein the coating material is applied to the end of the stator bar through a chamber in the fitting. 
   
   
       11 . The method as in  claim 1  wherein the coating material is applied to the end of the stator bar as a solid. 
   
   
       12 . The method as in  claim 1  wherein the coating material comprises a group consisting of a paste, a powder, metallic chips and metallic shavings. 
   
   
       13 . A fitting for a stator bar of a generator comprising:
 a fitting housing having a collar at a first end and a cooling fluid coupling at an opposite end, wherein said collar is brazed with a braze material to an end of the stator bar;   a chamber extending from the first end to the opposite end of the fitting, and   a metallic barrier coating on an end of the stator bar in said chamber and forming a seal between the end and a remaining portion of the chamber, wherein said metallic barrier coating has a liquidus temperature lower than a solidus temperature of the braze material applied to braze the stator bar to the fitting.   
   
   
       14 . A fitting as in  claim 13  wherein the metallic barrier coating is a tin-silver copper alloy. 
   
   
       15 . A fitting as in  claim 13  wherein said stator bar comprises solid copper strands and hollow copper strands, wherein the end of the stator bar further comprises ends of the solid copper strands and ends of the hollow copper strands extending beyond the ends of the solid copper strands, and wherein the coating covers the ends of the solid copper strands and the ends of the hollow copper strands extend through the coating. 
   
   
       16 . A fitting as in  claim 13  wherein said stator bar comprises solid copper strands and hollow copper strands, wherein the end of the stator bar further comprises inserts in open of the hollow copper strands, and wherein the coating covers ends of the solid copper strands and the inserts extend through the coating. 
   
   
       17 . A fitting as in  claim 16  wherein the inserts are ceramic. 
   
   
       18 . A fitting as in  claim 13  wherein a thickness of the coating is in a range of 10 to 500 mils.