RB and RQ shunted BusBar current carrying capacities Daniel Molnar

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

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)

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

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

Comparisons, Validations The QP3 and Comsol 4.1.0.88 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

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

RQ/RB non shunted

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

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

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

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

RB up shunt The minimum detectable void

RQ below shunts The minimum detectable void Symmetric defects Asymmetric defects

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

RQ Side-shunt zl zm zr x 15 8

RQ sideshunt type_b zb 15 zj x x z y

RQ shunts summary

Different Time constants(Tau)

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

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.)

Acknowledgement Many thanks to Arjan Verweij and Erwin Bielert

Back up slides

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

Extreme case: full length non stabilized cable

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

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

Defect look-a-like

Magnetic models, mesh quality

Magnetic effects: First results

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

Modeled RQ side shunts

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