METHOD OF BRAZING A LIQUID-COOLED STATOR BAR

• US 20040216301A1
• Filed: 04/30/2003
• Published: 11/04/2004
• Est. Priority Date: 04/30/2003
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Iverson, Alan M., Rowe, Raymond Grant
• Granted Patent: US 7,073,247 B2
• Time in Patent Office: Days
• US Class Current: 29/596
• CPC Class Codes: B23K 1/0008 specially adapted for particular articles or work
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: H01R 4/029 Welded connections H01R4/021 - H01R4/028 take precedence
• CPC Class Codes: H01R 4/62 Connections between conductors of different materials; Connections between or with aluminium or steel-core aluminium conductors H01R4/68 takes precedence
• CPC Class Codes: H01R 9/11 End pieces for multiconductor cables supported by the cable and for facilitating connections to other conductive members , e.g. for liquid cooled welding cables
• CPC Class Codes: H02K 15/0093 Manufacturing or repairing cooling fluid boxes, i.e. terminals of fluid cooled windings ensuring both electrical and fluid connection
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine
• CPC Class Codes: Y10T 29/49169 Assembling electrical component directly to terminal or elongated conductor
• CPC Class Codes: Y10T 29/49179 by metal fusion bonding
• CPC Class Codes: Y10T 29/49393 with metallurgical bonding
• CPC Class Codes: Y10T 29/49719 Seal or element thereof
• CPC Class Codes: Y10T 29/49728 and by a metallurgical operation, e.g., welding, diffusion bonding, casting
• CPC Class Codes: Y10T 29/49742 Metallurgically attaching preform
• CPC Class Codes: Y10T 29/49746 by applying fluent material, e.g., coating, casting

Abstract

A method for metallurgically bonding a stator bar to a coupling to reduce the incidence of leak paths resulting from corrosion. The stator bar comprises strands through which a liquid coolant can flow. Adjacent ends of the strands are received in an interior cavity of the coupling through an opening in the coupling. A joining material is provided on a first portion of the stator bar within the coupling opening and adjacent the ends of the strands. The first portion is heated to melt the joining material. At essentially the same time, a second portion of the stator bar outside the coupling is also heated. Once the joining material is suitably molten, the first portion is allowed to cool while the second portion remains heated, thereby causing the joining material nearest the ends of the strands to solidify first.

Claims

1. A method of metallurgically bonding a stator bar to a coupling having an interior cavity and an exterior opening thereto, the stator bar comprising a group of strands having adjacent ends received in the coupling through the opening of the coupling, the method comprising the steps of:

providing a joining material located on a first portion of the group of strands within the coupling and adjacent the ends of the strands;

heating the first portion of the group of strands to melt the joining material within the coupling and heating a second portion of the group of strands outside the coupling;

cooling the first portion of the group of strands to initiate solidification of the joining material nearest the ends of the strands while continuing to heat the second portion of the group of strands; and

then

cooling the second portion of the group of the strands;

wherein cooling of the first portion of the group of strands prior to cooling of the second portion of the group of strands causes the joining material to solidify in a direction away from the ends of the strands and toward the second portion, the joining material metallurgically bonding the strands to each other and bonding the first portion of the group of strands to the coupling so as to form a fluid-tight joint therebetween.

2. The method according to claim 1, wherein at least some of the strands are hollow.

3. The method according to claim 1, wherein the heating steps are performed with a first heating means in proximity to the coupling and a second heating means in proximity to the second portion of the group of strands.

4. The method according to claim 1, further comprising the step of directing a cooling gas at the coupling to promote cooling and solidification of the joining material nearest the ends of the strands.

5. The method according to claim 1, wherein the coupling further comprises a heat sink thermally coupled thereto, the method further comprising the step of removing the heat sink after the step of cooling the second portion of the group of the strands.

6. The method according to claim 1, further comprising the step of placing a fitting around the second portion of the group of strands, wherein the step of heating the second portion of the group of strands serves to heat the fitting.

7. The method according to claim 6, further comprising the step of providing a second joining material at the second portion of the group of strands, wherein the step of heating the second portion of the group of strands serves to heat the fitting and melt the second joining material, and the step of cooling the second portion causes the second joining material to solidify and metallurgically bond the fitting to the second portion.

8. The method according to claim 1, wherein any surface defects in the joint are concentrated in a region of the joint farthest from the ends of the strands as a result of the directional solidification of the joining material.

9. The method according to claim 1, wherein the joining material completely solidifies before cooling the second portion of the group of the strands.

10. A method of metallurgically bonding a stator bar to a coupling having an interior cavity and an exterior opening thereto, the stator bar comprising a bundle of metal strands having adjacent ends, the method comprising the steps of:

providing a first brazing material on a first portion of the stator bar adjacent the ends of the strands and providing a second brazing material on a second portion of the stator bar spaced apart from the first portion;

assembling the stator bar with the coupling and an annular-shaped fitting so that the ends of the strands are received in the coupling through the opening thereof, the first portion of the stator bar is within the opening, and the second portion of the stator bar is outside the opening;

placing a first heating means in proximity to the coupling and placing a second heating means in proximity to the fitting;

operating the first heating means to heat the coupling and the first portion therein and thereby melt the first brazing material, and operating the second heating means to heat the fitting and the second portion therein and thereby melt the second brazing material;

operating the first heating means to allow the first portion of the stator bar to cool and thereby initiate solidification of the first brazing material nearest the ends of the strands while continuing to operate the second heating means to maintain the second brazing material in a molten state, the first brazing material solidifying in a direction away from the ends of the strands and toward the second portion of the stator bar; and

then

operating the second heating means to allow the second portion of the stator bar to cool and thereby cause the second brazing material to solidify;

wherein the first brazing material metallurgically bonds the strands to each other and the first portion of the stator bar to the coupling so as to form a fluid-tight first brazement therebetween, the second brazing material forms a second brazement that metallurgically bonds the second portion of the stator bar to the fitting, and any surface defects in the first brazement are concentrated in a region of the first brazement farthest from the ends of the strands as a result of the directional solidification of the first brazing material.

11. The method according to claim 10, wherein the strands, the coupling and the fitting are formed of copper or alloys thereof.

12. The method according to claim 10, wherein the coupling and the fitting are formed of first and second materials, respectively, and the second material has a higher electrical resistivity than the first material.

13. The method according to claim 10, wherein at least some of the strands are hollow and a remainder of the strands are not hollow.

14. The method according to claim 10, wherein the first and second heating means are induction coils.

15. The method according to claim 10, further comprising the step of directing a cooling gas at the coupling to promote cooling and solidification of the first brazing material before solidification of the second brazing material.

16. The method according to claim 10, wherein the coupling further comprises a heat sink thermally coupled thereto, the method further comprising the step of removing the heat sink after the step of operating the second heating means to allow the second portion of the stator bar to cool.

17. The method according to claim 16, wherein the heat sink is mechanically fastened to the coupling, and the step of removing the heat sink comprises unfastening the heat sink from the coupling.

18. The method according to claim 16, wherein the heat sink is an integral portion of the coupling, and the step of removing the heat sink comprises cutting the heat sink from the coupling.

19. The method according to claim 10, wherein the fitting is immediately adjacent but spaced apart from the coupling.

20. The method according to claim 10, wherein the first brazing material completely solidifies before the second heating means is operated to cool the second portion of the stator bar.