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NCSX Peer Review Modular Coil Electrical Joint. James Chrzanowski April 24, 2006. 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? - PowerPoint PPT Presentation
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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
191jumper
181jumper
181jumper
240Lug
240Lug
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
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