TF Coil Preload Design Iteration 2/23/05

1

NCSX

TF Coil Radial PreloadRequired for Structural Stability

• A. Brooks has identified some time points in the reference current scenarios which produce an unstable force distribution on the TF coils (positive net radial force and torque about major radius).

• This occurs when MC currents are high and the TF coil current is relatively low.

TF Coil Preload Design Iteration 2/23/05

2

NCSX

Comparison of Deformations fromSlipped and Stuck TF Coils

Zero Radial Preload Allows Coils to Slip at Interface

(old 2x6 WP)

Radial Preload Sufficient to “Stick” Coils at Interface

(new 3x4 WP)

TF Coil Preload Design Iteration 2/23/05

3

NCSX

Wedge-to-Wedge Friction Coefficient ()as a Function of Radial Preload

• A 4000 lb preload will produce a “stuck” coil set if >0.1.• This is a factor of 2 below the 0.2 value which is expected

to be easily achieved.

Fig. 4.1-6 Average Surface Friction Coeffieint as a Function of Radial Preload

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 1000 2000 3000 4000 5000

Radial Preload, lbf/bracket

Av

e. F

ric

tio

n C

oe

ffic

ien

t

TF Coil Preload Design Iteration 2/23/05

4

NCSX

Radial Preload Applied to Back Leg

• Radial pre-load required to ensure wedging

Wedging

Radial Pre-load

SS WedgeCastings

Back SS Strap

TF Coil Preload Design Iteration 2/23/05

5

NCSX

Breakout of Reaction Structures, Radial Preload

• Radial preload applied with jack screw device top and bottom.

• 4,000 LBF per pusher provides twice the required pre-load to prevent any movement as TF Fields ramp up or down

• Bellville washers in parallel provide relatively constant force over required thermal excursions

TF Coil Preload Design Iteration 2/23/05

6

NCSX

Breakout of Reaction Structures, Wedging

Wedging Extends 50 degrees around the upper and lower TF

Castings extend as High as the Upper TF Support Castings

Wedging fixes location while shim bags lock coil in case with respect to supports

Locking Pins add redundancy to wedging design

TF Coil Preload Design Iteration 2/23/05

7

NCSX

Centering Forces for TF Only

• Centering forces concentrate on inner leg

• Moving preload to inner leg removes unnecessary stress

TF Coil Preload Design Iteration 2/23/05

8

NCSX

Jack Screw Device Added Pulls Coil Forward

Bellville washers ensure constant 4000 lbf load

• Use available space for preload jacking screws instead of pins

TF Coil Preload Design Iteration 2/23/05

9

NCSX

Jack Screw Device Added Pulls Coil Forward

TF Coil Preload Design Iteration 2/23/05

10

NCSX

Top Down View, Center Stack

• Nuts accessible for maintenance from top of vessel

TF Coil Preload Design Iteration 2/23/05

11

NCSX

Access Holes In Top Hat Structure

• Removal of PF4 allows for access to bracket hardware

TF Coil Preload Design Iteration 2/23/05

12

NCSX

Jack Screw Device Added Pulls Coil Forward

TF Coil Preload Design Iteration 2/23/05

13

NCSX

TF Coil Bonded to Casting With Front Preload

• Model updated to reflect preload application at front of coil directly to wedge castings

TF Coil Preload Design Iteration 2/23/05

14

NCSX

Deflections With Front Preload and Cool Down

• Preload contributes little or no deflection before application of operating load

TF Coil Preload Design Iteration 2/23/05

15

NCSX

Stresses Due to Preload + .5Tesla TF Only Operation

• Compares to 195 MPa for unbonded back leg preload run

• Bonded Bending Stress at 127 MPa

• Early results show about 177 MPa for unbonded front preload

TF Coil Preload Design Iteration 2/23/05

16

NCSX

New TF Flag Design

TF Coil Preload Design Iteration 2/23/05

17

NCSX

Breakout of Reaction Structures, Vertical Support

• Lower Support reacts gravity load and fixes vertical position.

• Allows for Outward radial motion

• Upper Support allows for application of upward or downward load.

• Allows for Outward radial motion