NSTX TF Flag JointDesign Review
OVERVIEW
C Neumeyer8/7/3
Topics
• Requirements• Forces• Load Paths • Temperatures and Thermal Effects• Contact Resistance• Features of New Design
FIELD AND CURRENT
• Base GRD requirement:
3kG at R0=0.854m with 4.5 sec flat top, once every 300s
35580 Amp with 36 turn coil
• High field GRD requirement:
6kG at R0=0.854m with 0.6 sec flat top, once every 300s
71160 Amp with 36 turn coil
0
10
20
30
40
50
60
70
80
-1 0 1 2 3 4 5 6
6kG Full I2T L/R
108712
3kG Full I2T L/R
CURRENT WAVEFORMS• Engineering design accounts for PS response, inc’l L/R decay in case of fault from Imax
• ∫I2T = 6.0 x 109 A2-s for 3kG-4.5s
• ∫I2T = 6.15 x 109 A2-s for 6kG-0.6s
• Design basis ∫I2T = 6.5 x 109 A2-s which causes adiabatic T of 80oC in Cu
• 6kG pulse is most critical for joint since forces are maximum and time for heat diffusion is minimum
NUMBER OF PULSES & THERMAL CYCLES
• Assume 50,000 pulse requirement at 6kG- 10 yr*20 week*5day*8hr*6pulse/hr = 48,000- Highly conservative- NSTX 5yr plan calls for ≈ 5% 6kG pulses plus…
40% @ 3kG (25% EM load) 40% @ 4kG (44% EM load) 15% @ 5kG (69% EM load)
• Assume 1,000 thermal ratcheting cycles (= number of days)- 10 yr*20 week*5day = 1000- drives flag fastener fatigue cycle requirement- assuming 12 pulse/hr rate to set thermal ratcheting (conservative)
VOLTAGES
• TF PS is 1kV DC no-load – 1012.85 volts DC avg– 1060 volts peak
• High resistance grounded, Vline-ground=500V nominal, 1kV max• CHI can elevate hub assembly and OH tension tube to 1kV• Max design voltages:
– turn-to-turn = 1000/36 ~ 30V for adjacent conductors, 1kV max– turn-to-ground (hub and OH tension tube) = 2kV– base hipot = 2E+1= 5kV– routine hipot ~ 3kV
EM FORCES
• In-Plane-vertical load and momentdue to magnetic pressure from self-field
• Out-of-Plane-lateral due to ItfxBz(oh&pf)
-torsional due to ItfxBr(oh&pf)
IN-PLANE FORCESComponent Force
(lbf)
Moment
(in-lbf)
Outer Layer Flags (24 turns)
9235 31719
Inner Layer Flags (12 turns)
2309 14343
Total All Turns 249325
Notes: 1) Bt=6kG2) Forces include accumulation midway through flex link
OUT-OF-PLANE FORCESComponent Force
(lbf)
Moment
(in-lbf)
Inner Tier Flag/Link 4698 55609
Outer Tier Flag/Link 3039 37174
Total All Turns 149198 1.78e6
Inner Legs below Flags 4.90e5
Notes: 1) Bt=6kG2) OH and all PF at maximum current3) OH contribution is bi-directional
LOAD PATHSSpline JointUmbrellaOuter LegFlexHubFlagVesselAnchorTorque CollarWet Lay-upInner Leg BundleFEMShearShoe
1) Friction2) Shear Shoe3) Torque Collar4) Hub/Spline/VV
TEMPERATURES
• Inner Leg- TSOFT = 29oC- TEOFT = 66oC- TEOP = 95oC (worst case)
• Wet lay-up & collar- negligible T
THERMAL EFFECTS•Vertical length of inner leg bundle from bottom to top increases by up to 0.35” during a pulse
•Vertical length of inner leg from torque collar to top of bundle increases due to inner leg temperature rise, whereas flag and hub remain relatively cool
•Radius of inner leg bundle increases bundle increases by approximately 0.006” during a pulse
•Flag heats modestly during pulse (T ≈ 5oC) but can ratchet to T ≤25oC at rated duty cycle (conservative), r ≈ 0.005” in length
CONTACT PRESSURE & RESISTANCE
Contact Resistivity vs. Pressure, Fit=IF(p<1500, 3.952-2.074e-3*p,14.482*p^-0.392)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 2000 4000 6000 8000
Pressure (psi)
Contact Resistivity (microohm-in^2)
Measured DataFit
CONTACT RESISTANCEFlat Top Time to Limit Max Temperature
at Joint to 120 C 71 KA Waveform, L/R Decay
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 1 2 3 4 5 6 7 8
Contact Resistance, μΩ- 2in
, Flat top sec
120 C Liμit at Joint~80 C Liμit in Turn
Req’d Flat Top Time=0.6 sec
TolerableResistivity≈ 2.5µΩ-in2
(700psi)
Note: assuming constant resistivity along joint
KEY DESIGN FEATURES
Flag
Flag bolt (stud)
Shear Shoe
Flag Box
Box Bolt (stud)Collar
Hub Disk
Probe Tail
TORQUE COLLAR
VOLTAGE PROBES• IDI 100526 Coax Probe terminated in SMB connector
-commercial spring loaded probe used in semiconductor test industry
DESIGN HIGHLIGHTS• Solid flags w/2 half-lapped layers Kapton, glass wrapped, potted in 304SS boxes
• Boxes bolted to the hub disks using 5/8” hardware
• Flags attached via 3/8” Inconel bolts (studs) preloaded to 5000lbf
• Shear shoe on outer edge of flags is bolted to ends of inner leg conductor using Inconel bolts, one vertical and one angled for moment reaction
• 3-segment torque collar w/two 1/2” A286 bolts/6000lbf belleville washers per joint, 0.180” wet lay-up (Hysol E-120HP), 1ksi min. compression
• Collar transmits torque to hub structure at 3 anchor points
• Redundant voltage probes are located on each side of the flag