METHOD AND SYSTEM FOR APPLYING AN ISOLATION LAYER TO A BRAZED END OF A GENERATOR ARMATURE WINDING BAR

• US 20060108355A1
• Filed: 11/19/2004
• Published: 05/25/2006
• Est. Priority Date: 11/19/2004
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Breznak, Jeffrey Michael, Hopeck, James Fredrick, Sowers, Lawrence Lee, Iversen, Alan Michael
• Granted Patent: US 7,199,338 B2
• Time in Patent Office: Days
• US Class Current: 219/615
• CPC Class Codes: B23K 1/0008 specially adapted for particular articles or work
• 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

Abstract

A method of forming a brazed joint between an armature bar and a hydraulic header clip including: assembling an end of the armature bar, hydraulic header clip and a substantially phosphorous-free braze material; positioning the assembly of the armature bar, hydraulic header clip and the braze material in a braze chamber, such that the clip is seated in an induction heating coil; heating the assembly to a first temperature within 200 degrees Fahrenheit of and below a solidus temperature of the braze material by applying electrical current to the induction heat coil; heating the assembly to a second temperature above the liquidus temperature of the braze material; pooling liquid braze material on ends of the armature bar, and cooling the assembly and thereby forming a braze layer on the end of the armature bar.

Claims

1. A method of forming a brazed joint between an armature bar and a hydraulic header clip comprising:

a) assembling an end of the armature bar, hydraulic header clip and a substantially phosphorous-free braze material;

b) positioning the assembly of the armature bar, hydraulic header clip and the braze material in a braze chamber, such that the clip is seated in an induction heating coil;

c) heating the assembly to a first temperature within 200 degrees Fahrenheit of and below a solidus temperature of the braze material by applying electrical current to the induction heat coil;

d) heating the assembly to a second temperature above the liquidus temperature of the braze material;

e) pooling liquid braze material on ends of the armature bar, and

f) cooling the assembly and thereby forming a braze layer on the end of the armature bar.

2. The method of claim 1 wherein steps (b) to (f) are performed in an substantially oxygen free atmosphere within the braze chamber.

3. The method of claim 2 wherein the substantially oxygen free atmosphere is substantially nitrogen and hydrogen.

4. The method of claim 2 wherein the oxygen free atmosphere is substantially all hydrogen.

5. The method of claim 2 wherein the substantially oxygen free atmosphere has an oxygen level of less than 400 parts per million.

6. The method of claim 1 further comprising applying a force to the clip during heating to compress the assembly.

7. The method of claim 6 wherein the force is applied to a side cover of the clip and said side cover is juxtaposed against the armature bar.

8. The method of claim 7 the force is in a range of 100 to 1,800 pounds.

9. The method of claim 1 wherein said armature bar is positioned vertically in the chamber and the bar comprises solid strands and hollow strands having free hollow ends extending axially beyond solid free ends of said solid strands.

10. The method of claim 1 wherein the armature bar comprises solid and hollow strands formed of at least one of copper, copper-nickel alloys and stainless steel.

11. The method of claim 10 wherein assembling the end of the armature bar comprises interleaving the braze alloy between the strands and positioning braze alloy axially beyond the solid free ends and no further than the hollow free ends.

12. The method of claim 10 wherein said braze material comprises strips of a silver based braze alloy interleaved between the strands.

13. The method of claim 1 wherein the heating to the second temperature is held for a period of 5 to 100 seconds.

14. The method of claim 13 wherein the heating to the first temperature is held for a period of 30 to 600 seconds.

15. The method of claim 1 wherein the first temperature is within 50 degrees of solidus.

16. The method of claim 1 further comprising applying a heat sink to a portion of the armature bar in the chamber and axially beyond the hydraulic header clip while the clip is heated.

17. A method of forming a brazed joint between an armature bar and a hydraulic header clip comprising:

a) assembling free ends of hollow strands and of solid strands of the armature winding bar and positioning the assembly within the hydraulic header clip;

b) interleaving a silver based braze alloy between the strands, wherein a portion of the braze alloy extends axially beyond the free ends of a plurality of the solid strands and the free ends of a plurality of the hollow strands extend axially beyond the braze material;

c) positioning the assembly of the free ends, hydraulic header clip and the braze alloy in a braze chamber, such that the clip is seated in an induction heating coil of the chamber;

d) heating the assembly to a first temperature below a solidus temperature of the braze alloy and within a 200 degrees Fahrenheit of the solidus temperature activating the induction heat coil to heat the clip;

e) heating the assembly to a second temperature above the liquidus temperature of the braze alloy;

f) pooling liquid braze alloy on ends of the armature bar, and

g) cooling the assembly and clip thereby forming a braze isolation layer on the end of the armature bar.

18. The method of claim 17 further comprising heating the assembly to the first and second temperature in an atmosphere comprising at least one of a mixture of nitrogen and hydrogen and all hydrogen.

19. The method of claim 18 wherein the atmosphere is substantially nitrogen and hydrogen.

20. The method of claim 18 wherein the atmosphere has an oxygen level of less than 400 parts per million.

21. The method of claim 17 further comprising applying a force to the clip during heating to compress the assembly.

22. The method of claim 21 wherein the force is applied to a side cover of the clip and a clip cover is juxtaposed against the armature bar.

23. The method of claim 21 the force is in a range of 100 to 1,800 pounds.

24. The method of claim 17 wherein the heating to the second temperature is for a period of 5 to 100 seconds.

25. The method of claim 24 wherein the heating to the first temperature is for a period of 30 to 600 seconds.

26. The method of claim 17 wherein the first temperature is within 50 degrees of solidus.

27. The method of claim 17 further comprising applying a heat sink to a portion of the armature bar in the chamber and axially beyond the hydraulic header clip while the clip is heated.

28. A system for forming a brazed joint between an armature winding bar and a hydraulic header clip comprising:

an assembly of free ends of hollow strands and solid strands of the armature winding bar positioned within the hydraulic header clip;

a silver based braze alloy interleaved between the strands, wherein a portion of the braze alloy extends axially beyond the free ends of a plurality of the solid strands and the free ends of a plurality of the hollow strands extend axially beyond the braze material;

said assembly of the free ends, hydraulic header clip and the braze alloy mounted a braze chamber, such that the clip is seated in an induction heating coil of the chamber, and

a controller receiving a temperature feedback signal from a temperature sensor in the chamber and controlling a temperature in the chamber by controlling power applied to the coil and based on the feedback signal,

wherein during a brazing period said coil heats the assembly to a temperature above the liquidus temperature of the braze alloy.

29. The system of claim 28 wherein the coil first heats the assembly to a temperature below a solidus temperature of the braze alloy and within a 200 degrees Fahrenheit of the solidus temperature.

30. The system of claim 28 wherein an atmosphere in the chamber is substantially nitrogen and hydrogen during the brazing period.

31. The system of claim 30 wherein the atmosphere has an oxygen level of less than 400 parts per million.

32. The system of claim 28 further comprising a ram arranged to applying a force to the clip during the braze period.

33. The system of claim 32 wherein the ram applies a force to a side cover of the clip and a clip cover is juxtaposed against the armature bar.

34. The system of claim 32 wherein the force is in a range of 100 to 1,800 pounds.

35. The system of claim 28 further comprising a heat sink applied to a portion of the armature bar in the chamber and axially below the hydraulic header clip.