Preliminary results of the partial array LCT coil tests Page: 4 of 5
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recorded on multichannel tape recorders, continuously
at first and later only when AE signals were expected.
Two channels (sensor #16 on the outer leg of GD,6
and bobbin at the smallest radius of JA3) were also
observed in real time on a scope. Preliminary results
(1) Large and frequent AE signal bursts were observed
whenever either coil was charged to a new current
level for the first time. Smaller and much leas
frequent bursts were seen on subsequent runs oC GD.
(2) Some bursts coincided with spikes in the compen-
sated voltage, these originated with conductor motion;
more occurred without such coincidence, implicating
(3) Few bursts were seen on GD for current discharge
or dump, more for JA, especially as lower currents
(4) Only a few small bursts were seen when the current
was held steady, unless the other coil was charging;
for JA, spikes in the compensated voltage also appear-
(5) No AE signal was actually observed when one-half
turn of the coil winding was driven normal by heater.
(6) For GD, AE activity seemed to die down after the
current was raised above 7.5 kA, indicating the (un-
bonded) winding was tightly bedded at that load. For
JA, AE activity continued to increase with current,
probably indicating that some glued bonds in the
winding were cracking.
Mechanical Behavior. From an engineering mechanics
viewpoint, three distinct Lorentz force loading condi-
tions occurred during the testing. These were (1) a
single coil at 100% of design current, (2) two coils
simultaneously at 40% of design current, and (3) one
coil at 40% while the other was at 100% of design
current. The first two of these loading conditions
were approximated within a finite element model9 (FEM)
for the originally proposed two-coil test. Calculated
values obtained from this FEM are the basis for the
comparison presented below. For various reasons, this
FEM contained only two coils, both of which were
modeled identically to reflect the gross mechanical
aspects of the GD coil. The third loading condition
was not treated.
When a single coil is energized to 100% of its
design current, the magnetic forces tend to make the
coil become more nearly circular. Changes in bore
dimensions were monitored by specially designed Moving
Coil Displacement Transducers.10 The horizontal bore
increase for the GD coil was 100 to 109 mils compar-
ed to a calculated value of 91. The vertical bore
decrease for the GD coil was 37 to 47 mils compared to
a calculated value of 40. Values for the JA coil were
slightly higher. The winding displacements within the
coil cases were measured. Figure 8, for an unbonded
-2 0 2 4 6
8 10 12
winding (GD), shows outward motion for the bobbin and
toward the OD ring, compaction from the ends, and
significant bedding-down, all as expected. Curves
taken with both coils energized are more complicated,
but also understandable. Similar data from the JA
coil shows much less displacement and bedding-down.
presumably reflecting its turn-to-turn bonding. As
the winding pack model was extremely crude in the FEN,
comparison of calculated values with these data await
an updated and more refined model.
When both coils were simultaneously energized to
40% f their design current, the out-of-plane magnetic
forces towards each other tend to squeeze the torque
rings out from between the two coils. The torque ring
spokes, which hold the torque ring in place, restrain
this motion and thus develop large loads. The torque
ring bending strain for this loading condition was
measured to be 200 1t which compares favorably to a
calculated value of 227 Pc. The spoke strain was
340 tic which compares to a calculated value of 333 pc.
Both calculated values were obtained by applying I2
scaling to the FEM values because the only loading
condition in the FEM that applied was that of 100% of
design current in both coils.
A red-line strain limit of 1500 uc was in effect
during the 40-100 simultaneous coil testing. This
value was nearly reached in the spokes. Comparison
with the FEM awaits completion of an analogous loading
1. P. N. Haubenreich et al., "Startup of Large Coil
Test Facility," to be presented at the 13th
Symposium on Fusion Technology, Varese, Italy,
September 24-28, 1984.
2. J. A. Zichy et al., "Instrumentation and Test of
the Swiss LCT-Coil," this conference.
3. S. Shimamoto et al., IEEE Trans. Man., MAG-19,
4. J. N. Luton, Jr. et al., p. 547 in Proc. 9th
Symp. on Engr. Prob. of Fusion Research, IEEE
H. T. Yeh et al., p. 1802 in Proc. 9th Symo. on
Engr. Prob. of Fusion Research, IEEE (1981).
E. H. Christensen and S. D. Peck, Adv. in Cryo-
genic Engr. 27, 327 (1982).
E. H. Christensen and S. D. Peck, General Dynamics
Report GDC91ZO122, July 10, 1980.
K. Jacob et al., p. 754 in Proc. 10th Symo. on
Fusion Engr. (1983).
W. H. Gray and T. V. Baudry, ASME, AMD-49, 81
J. F. Ellis and P. L. Walstrom, US Pat. 04,030,085
June 14, 1977.
A 4 4 5
Fig. 8. GD winding movement away from the coil case.
START: 8/28/84 18:0.7
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Luton, J.N.; Cogswell, F.D.; Dresner, L.; Friesinger, G.M.; Gray, W.H.; Iwasa, Y. et al. Preliminary results of the partial array LCT coil tests, article, September 10, 1984; United States. (digital.library.unt.edu/ark:/67531/metadc1205208/m1/4/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.