BusBar current carrying capacities Daniel Molnar 1 Physical description Joule heating is implemented Also magnetic effects are taken into consideration SFF Self Field Factor The effective field later ID: 503622
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Slide1
RB and RQ shunted BusBarcurrent carrying capacities
Daniel Molnar
1Slide2
Physical description
Joule heating is implemented Also magnetic effects are taken into considerationSFF: Self Field Factor
The effective field later
Material parameters are all Temperature dependent, exp decaying current, etc. : highly non linear problem
Conservative values for materials, time constants, boundary and initial conditions are used (eg.:T0=10K) and definition of “safe” currentCompletely Adiabatic case, no cooling to HE
2Slide3
Main model descriptions
If possible symmetry is used to speed up the calculationsRectangular elements, with same area as “real” shape for modeling reasons (same results)
Perfect splice between the two cables in the interconnection
Non stabilized length of the cable by default is 15mm(below the “tongue” of BUS)
3Slide4
Symmetries used in the models
4
Type a) :parallel to the length typically in RB simulations, but in some RQ as well
Type b): perpendicular to the lengthSlide5
Material properties
5
Nb
-Ti electrical resistivity
Copper thermal conductivity
Copper electrical resistivity
For metals (Cu(RRR),solders, cable is
mixture
):
(Magnetic effects)Slide6
Comparisons, Validations
The QP3 and Comsol 4.1.0.88 comparisonsVarious cases have been compared, the most interesting ones are mentioned hereFirst a one D model was taken
Then 3D with the half of the length (also “full” length)
And then shunted comparisons
All were fit to each other in order to compare properly6Slide7
Defect types for non shunted
7
15
15
-In the non-shunted case the non stabilized length of the cable “moves” towards the BUS
BUS
wedge
U-profile
BUS
Stabilized cable(i.e. well soldered)
Non soldered cable
Non soldered cable
Y
XSlide8
RQ/RB non shunted8Slide9
RB up shunt9
-Note that the two reservoir holes are always considered to be AIR, with rectangular shape
-The defect of
SnPb
solder is indicated by green lines, different lengths of it
-also non perfect contact betweenwedge and U-profile
Top view for up-shunt
15
Wedge
U-profileSlide10
RQ/RB below shunt
10
15
Bottom view below shunt
-The shunt is the same as for the up one
-The defect of
SnPb
solder is indicated by green lines, different lengths of it
-Also the defect is symmetric with respect to the connection of Bus and U profileSlide11
Description of symmetric shunt defects
11
50
15
Holes
Up shunt
Below shunt
BUS
wedge
U-profile
BUSSlide12
RQ below
shunt:Temperature and current
distribution
12
Temperature distribution in X-Y
Current density Z componentSlide13
RB up shunt13
The minimum detectable voidSlide14
RQ below shunts
14
Symmetric defects
Asymmetric defects
The minimum detectable voidSlide15
Current density Y component
The current “flow”
RQ below
shunts-length of the shunt
15
Length of shunt [mm]
Current density
Y
Current density
Y
Length of shunt [mm]Slide16
RQ Side-shunt16
8
15
zl
zm
zr
xSlide17
RQ sideshunt type_b
17
x
z
y
zb
15
zj
xSlide18
RQ shunts summary18Slide19
Different Time constants(Tau)
19Slide20
The effect of the SnPb thickness
The “standard” is 100 mm but , also the effect of a thicker
SnPb
layer under (or above) the shunt has been investigated
For an RB below shunt with 8mm of GAP in the SnPb -100 mm thickness:16200 A -300 mm thickness:15900 A
20Slide21
Conclusions
QP3 and Comsol 4.1 results are correlating very well (within less than 8 % difference)The main shunts are capable to carry more than 13 kA and no gain with longer shunt
The margin is bigger for
Quadropole
shuntsThe safe current is less than 13 kA for the side shunts with original design parameters, but modified ones could be fineThe safe current also highly depends on the distribution and the size of both defectsWith Comsol it is possible to implement any type of geometry or/and physical effects (cooling etc.)
21Slide22
Acknowledgement
Many thanks to Arjan Verweij and Erwin Bielert
22Slide23
Back up slides
23Slide24
QP3 Comsol difference; shunt RRR 150
24
For RQ shunted calculations(0=0.5)
For RB shunted calculations (0=0.5)
QP3 the shunt’s RRR=150Slide25
Extreme case: full length non stabilized cable
25Slide26
Extreme case II) full length NSC,non symmetric SnPb defect
26Slide27
And a more Extreme:No Cu in the defect for RQ below shunt
27Slide28
Defect look-a-like
28Slide29
Magnetic models, mesh quality
29Slide30
Magnetic effects: First results
30Slide31
Different Time constants-same current
31
The safe current for Tau 30 sec:
16kA
(also a bd case)Slide32
Modeled RQ side shunts
32Slide33
An example of usage beyond Comsol
33
Resistance as a function of time; It could carry14kA without reaching 300 K, shunted version, no void in
SnPb