NCSX Peer Review Modular Coil Electrical Joint James

NCSX Peer Review Modular Coil Electrical Joint James Chrzanowski April 24, 2006 Modular Coil Electrical Joint 1

Peer Review Charge • Has adequate testing been performed to proceed with implementation? • Have all credible risks been adequately addressed? • Have special risks to C 1 [already VPI’d] been adequately addressed? • Are the design and procedure revisions adequately documented to proceed with implementation? Modular Coil Electrical Joint 2

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

Photo’s of C 1 Coil Joints Terminal Jumpers G-11 cr Insulators Coil Terminal Lugs Modular Coil Electrical Joint 4

History of Joint Issue • Following the VPI of C 1, 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 5

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

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 7

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 C 1 Modular Coil Electrical Joint 8

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 9

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 10

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 11

Temperature Cycle Tests • Three of the joints were processed through six Nitrogen to room temperature cycles. Their resistances were remeasured 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 whethere 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 12

Joint Test Data Joint no. #1 #2 #3 #4 #5 Pre-solder resistance 2 2 1 7 8 Post-solder resistance 0 0/1 0/1 Joint resistance post N 2 cycle tests - - 0 0 0 191 jumper 181 jumper 240 Lug Temperature on cable 0. 25 inch from connector °C Modular Coil Electrical Joint 13

Additional Tests- G-11 Insulator • During one of the soldering tests, a G-11 cr 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 14

C 1 Lead Repair • All of the modular coil joints can be soldered prior to VPI, except for C 1 that has been already completed. • A test was performed to determine whethere was any risk to the epoxy filled conductors • Results: • C 1: – No charring of the insulation – Surface temperature of the insulation did reach 240 °C – If process is used on C 1, the insulation would be protected with anti-heat paste or chill plate Modular Coil Electrical Joint 15

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 DNCSX-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 16

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 C 1. • Drawings will have to be revised via ECN • Revisit the Belleville washers being used. Lighter weight washers would allow for more motion. Clearance around connector New feed hole Modular Coil Electrical Joint 17

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 C 2 which is nearing readiness for VPI, then would be incorporated into the C 1 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 18