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

• US 20070164016A1
• Filed: 03/30/2007
• Published: 07/19/2007
• Est. Priority Date: 11/19/2004
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Iversen, Alan, Breznak, Jeffrey, Sowers, Lawrence, Hopeck, James
• Granted Patent: US 7,405,379 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 phosphorus-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 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 in 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.

2. The system of claim 1 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.

3. The system of claim 1 wherein an atmosphere in the chamber is substantially nitrogen and hydrogen during the brazing period.

4. The system of claim 3 wherein the atmosphere has an oxygen level of less than 400 parts per million.

5. The system of claim 1 further comprising a ram arranged to applying a force to the clip during the braze period.

6. The system of claim 5 wherein the ram applies a force to a side cover of the clip and a clip cover is juxtaposed against the armature bar.

7. The system of claim 5 wherein the force is in a range of 100 to 1,800 pounds.

8. The system of claim 1 further comprising a heat sink applied to a portion of the armature bar in the chamber and axially below the hydraulic header clip.

9. The system of claim 1 wherein the braze chamber is adapted to provide a substantially oxygen free atmosphere for brazing.

10. The system of claim 9 wherein the substantially oxygen free atmosphere is substantially nitrogen and hydrogen.

11. The system of claim 9 wherein the oxygen free atmosphere is substantially all hydrogen.

12. The system of claim 9 wherein the substantially oxygen free atmosphere has an oxygen level of less than 400 parts per million.

13. The system of claim 1 wherein said armature bar is positioned vertically in the chamber.

14. The system of claim 1 wherein the bar comprises solid strands and hollow strands having free hollow ends extending axially beyond solid free ends of said solid strands.

15. The system of claim 1 wherein the braze alloy is positioned axially beyond the solid free ends and no further than the hollow free ends.

16. The system of claim 1 wherein said braze material comprises strips of a silver based braze alloy interleaved between the strands.

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

18. A braze chamber assembly for forming a brazed joint between an armature winding bar and a hydraulic header clip comprising:

a braze chamber defining an oxygen-free environment to receive the armature winding bar and a braze alloy applied to an end of the bar;

a induction coil mounted within the chamber and having a seat to receive the armature winding bar;

a clamp to receive the armature winding bar and hold the bar in the oxygen-free environment 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 induction coil and based on the feedback signal,

wherein during a brazing period said coil heats the armature winding bar to a temperature above a liquidus temperature of the braze alloy applied to the armature winding bar.

19. A braze chamber assembly as in claim 18 wherein the clamp holds the bar in a substantially vertical position such that the end of the bar is facing upward.

20. A braze chamber assembly as in claim 18 wherein the clamp is proximate to the induction coil and the clamp is a heat sink.