1. RB and RQ shunted BusBar current carrying capacities
Daniel Molnar

2. Physical description Joule heating is implemented
Also magnetic effects are taken into consideration
SFF: 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” current
Completely Adiabatic case, no cooling to HE

3. Main model descriptions
If possible symmetry is used to speed up the calculations
Rectangular 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)

4. Symmetries used in the models
Type a) :parallel to the length typically in RB simulations, but in some RQ as well
Type b): perpendicular to the length

5. Material properties For metals (Cu(RRR),solders, cable is mixture):
(Magnetic effects)
Nb-Ti electrical resistivity
Copper thermal conductivity
Copper electrical resistivity

6. Comparisons, Validations
The QP3 and Comsol comparisons
Various cases have been compared, the most interesting ones are mentioned here
First 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 properly

7. Defect types for non shunted
Stabilized cable(i.e. well soldered)
wedge 15
BUS
BUS
U-profile
Non soldered cable
-In the non-shunted case the non stabilized length of the cable “moves” towards the BUS Y
Non soldered cable X

8. RQ/RB non shunted

9. RB up shunt Top view for up-shunt 15
-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 between
wedge and U-profile
Wedge
U-profile

10. RQ/RB below shunt Bottom view below shunt 15
-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 profile

11. Description of symmetric shunt defects
Up shunt 50
Holes
wedge
BUS
BUS
U-profile
Below shunt 15

12. RQ below shunt:Temperature and current distribution
Temperature distribution in X-Y
Current density Z component

13. RB up shunt
The minimum detectable void

14. RQ below shunts The minimum detectable void Symmetric defects
Asymmetric defects

15. RQ below shunts-length of the shunt
Length of shunt [mm]
Current density Y
Current density Y
Length of shunt [mm]
The current “flow”
Current density Y component

16. RQ Side-shunt zl zm zr x 15 8

17. RQ sideshunt type_b zb 15 zj x x z y

18. RQ shunts summary

19. Different Time constants(Tau)

20. 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 mm thickness:16200 A
-300 mm thickness:15900 A

21. 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 shunts
The safe current is less than 13 kA for the side shunts with original design parameters, but modified ones could be fine
The safe current also highly depends on the distribution and the size of both defects
With Comsol it is possible to implement any type of geometry or/and physical effects (cooling etc.)

22. Acknowledgement
Many thanks to Arjan Verweij and Erwin Bielert

23. Back up slides

24. QP3 Comsol difference; shunt RRR 150
For RB shunted calculations (0=0.5)
For RQ shunted calculations(0=0.5)
QP3 the shunt’s RRR=150

25. Extreme case: full length non stabilized cable

26. Extreme case II) full length NSC,non symmetric SnPb defect

27. And a more Extreme:No Cu in the defect for RQ below shunt

28. Defect look-a-like

29. Magnetic models, mesh quality

30. Magnetic effects: First results

31. Different Time constants-same current
The safe current for Tau 30 sec:
16kA
(also a bd case)

32. Modeled RQ side shunts

33. An example of usage beyond Comsol
Resistance as a function of time; It could carry14kA without reaching 300 K, shunted version, no void in SnPb