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Evaluation of Modular Coil Electrical Joint for Implementation

This peer review examines the modular coil electrical joint, addressing risks, testing, and documentation for implementation. Joint resistance measurements and potential problems are discussed. A soldering procedure using silver-solder is proposed, along with tests for high resistant joints, temperature cycling, and G-11 insulator compatibility.

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Evaluation of Modular Coil Electrical Joint for Implementation

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  1. NCSXPeer ReviewModular Coil Electrical Joint James Chrzanowski April 24, 2006 Modular Coil Electrical Joint

  2. Peer Review Charge • Has adequate testing been performed to proceed with implementation? • Have all credible risks been adequately addressed? • Have special risks to C1 [already VPI’d] been adequately addressed? • Are the design and procedure revisions adequately documented to proceed with implementation? Modular Coil Electrical Joint

  3. Typical Modular Coil Joint Terminal Jumper or Lug Joint Torqued to 10 ft-lbs Conductor connector Belleville washers Flat washer Joint Resistance measured between these points Copper rope conductor Modular Coil Electrical Joint

  4. Photo’s of C1 Coil Joints G-11cr Insulators Terminal Jumpers Coil Terminal Lugs Modular Coil Electrical Joint

  5. History of Joint Issue • Following the VPI of C1, the joint resistances were measured. • Readings were between 2 to 254  [3/20/06] • Note: Joint measurements were not taken prior to VPI • After some working of the joints the joint resistances were measured. • Resistances dropped to 2 to 5  [4/7/06] • Closer examination of the joints revealed other potential problems with the joint assembly Modular Coil Electrical Joint

  6. A-3 2 [3/20] 2  [4/7] A-4 2 [3/20] 2  [4/7] A-2 2 [3/20] 2  [4/7] Side A A-1 5 [3/20] 2  [4/7] A-8 78 [3/20] 5  [4/7] A-7 23 [3/20] 2  [4/7] A-6 26 [3/20] 2  [4/7] Side B B-8 4 [3/20] 2  [4/7] A-5 254 [3/20] 2  [4/7] B-7 4 [3/20] 2  [4/7] B-6 4 [3/20] 2  [4/7] B-5 3 [3/20] 2  [4/7] B-4 3 [3/20] 2  [4/7] B-3 3 [3/20] 2  [4/7] B-2 3 [3/20] 2  [4/7] B-1 3 [3/20] 2  [4/7] C1- Joint Resistance Data 3/20/06 Original data post VPI 4/7/06 Data after re-work Modular Coil Electrical Joint

  7. Findings • Several of the conductor connectors protruded beyond the washer face of the jumper • This could prevent the connector from seating in the jumper or lug • The tolerance on the mating components [connectors & jumpers] could cause less then full contact • Full contact is never achieved • Finish and surface flatness of the connectors could have been better • Even if tolerances between contact faces were perfect, full surface to surface contact would not be achieved Modular Coil Electrical Joint

  8. Joint Test Program • Develop solder procedure • Prove that solder joints can be made in place • Demonstrate that high resistant joint can be improved using solder • Liquid nitrogen/room temperature cyclic tests • Shock solder joint at Nitrogen temperature • How would solder process effect epoxy/ insulation leads on C1 Modular Coil Electrical Joint

  9. Solder Joint • It was determined that the joint contact surfaces could be improved if the imperfections or misalignments were filled with electrical grade silver-solder • Solder connectors using silver-tin solder • Solder used: “Stay-Brite [J.W. Harris Co.] • 3.4 to 3.8% Silver/ balance Tin • Flow temperature: 430 °F/ 221 °C • Flux used: Rectorseal Nokorod E Regular paste flux • The joint will be heated using resistive heating unit Modular Coil Electrical Joint

  10. Solder Procedure • Pre-silver plate and assemble joint • Install appropriate hardware and torque to 10 ft-lbs • Position heating tongs around terminal jumper • Heat parts [430 °F/ 221 °C] • Feed flux from conductor side of connector • Feed silver-solder from conductor end of connector and feed hole Modular Coil Electrical Joint

  11. High Resistant Joint • Five test joints were made up with resistances varying between 2 and 8  • Several of these joints purposely had irregular surfaces and did not fit well. • It should be noted that during the preparation of these tests, some of the joints that measured 2  only had line contact where the lug and female connector met • Following the soldering operation all of the soldered joints were re-measured and had improved resistances between 0 to 1  Modular Coil Electrical Joint

  12. Temperature Cycle Tests • Three of the joints were processed through six Nitrogen to room temperature cycles. Their resistances were re-measured at 20 °C. • There was no change in the resistances [0 ] • Several of the joints were then cooled again to Nitrogen temperature. Once at temperature, they were hit with a soft face hammer to determine whether there was an evidence of the solder cracking as a result of physical shock. • There was no evidence of cracking or physical change in the solder. Modular Coil Electrical Joint

  13. Joint Test Data Modular Coil Electrical Joint

  14. Additional Tests- G-11 Insulator • During one of the soldering tests, a G-11cr insulator was positioned under the jumper to determine whether the operation would effect the pre-positioned insulators. • There was no physical change in color or appearance Jumper Modular Coil Electrical Joint

  15. C1 Lead Repair • All of the modular coil joints can be soldered prior to VPI, except for C1 that has been already completed. • A test was performed to determine whether there was any risk to the epoxy filled conductors • Results: • No charring of the insulation • Surface temperature of the insulation did reach 240 °C • C1: • If process is used on C1, the insulation would be protected with anti-heat paste or chill plate Modular Coil Electrical Joint

  16. Findings & Recommendations • The joint resistance of a typical modular coil joint can be greatly improved to 0 to 1  [Goal] • The solder operation does not effect the insulators or brazed connections • The soldering procedure would be incorporated in the D-NCSX-MCF-002 coil winding procedure as part of the present revision • Verification that the silver-solder being proposed can successfully be operated at liquid nitrogen temperatures [Dick Reed?] Modular Coil Electrical Joint

  17. Clearance around connector New feed hole Findings & Recommendations • The front taper of the conductor connectors will be modified to minimize the possible interference with the washers and joint hardware • A 3/32 inch solder feed hole would be added to each of the female jumpers and lugs, including C1. • Drawings will have to be revised via ECN • Revisit the Belleville washers being used. Lighter weight washers would allow for more motion. Modular Coil Electrical Joint

  18. Summary • The present joint design does not allow for future disassembly of all of the joints if required during maintenance periods. Solder joint will minimize these risks • This process if adopted would first be performed on C2 which is nearing readiness for VPI, then would be incorporated into the C1 joint assembly • The quality and integrity of the modular coil joints can be greatly improved by soldering the connectors to the jumpers and lugs after assembly Modular Coil Electrical Joint

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