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