Modular Coil Electrical Joint 1

NCSXPeer Review

Modular Coil Electrical JointJames 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

Conductor connector

Terminal Jumper or Lug

Copper rope conductor

Joint Torqued to 10 ft-lbs

Joint Resistance measured between

these points

Belleville washers

Flat washer

Modular Coil Electrical Joint 4

Photo’s of C1 Coil Joints

Terminal Jumpers

Coil Terminal Lugs

G-11cr Insulators

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

C1- Joint Resistance Data

Side A

Side B

A-878 [3/20]5 [4/7]

A-15 [3/20]2 [4/7]

A-22 [3/20]2 [4/7]

A-32 [3/20]2 [4/7]

A-42 [3/20]2 [4/7]

A-5254 [3/20]2 [4/7]

A-626 [3/20]2 [4/7]

A-723 [3/20]2 [4/7]

B-13 [3/20]2 [4/7]

B-23 [3/20]2 [4/7]

B-33 [3/20]2 [4/7]

B-43 [3/20]2 [4/7]

B-53 [3/20]2 [4/7]

B-64 [3/20]2 [4/7]

B-74 [3/20]2 [4/7]

B-84 [3/20]2 [4/7]

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

Dissected Joint

Modular Coil Electrical Joint 13

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 14

Joint Test Data

Joint no. #1 #2 #3 #4 #5

Pre-solder resistance 2 2 1 7 8

Post-solder resistance 0 0 0 0/1 0/1

Joint resistance post N2 cycle tests

- - 0 0 0

Temperature on cable 0.25 inch from connector °C

191

jumper

181

jumper

181

jumper

240

Lug

240

Lug

Modular Coil Electrical Joint 15

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 16

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 17

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 18

Findings & Recommendations

New feed hole

Clearance around connector

• 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 19

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