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Nr 4: Peak Field Calculation

Goal

Calculate peak fields in strands, position on the load line, temperature margins, and enthalpy margins to quench.

Description

  • 2D Options:
  • Fields & forces = TRUE makes ROXIE calculate the magnetic field and Lorentz forces in the position of every line current in the model. If N1*N2 in the Block Data 2D widget equals the number of strands, then this is exactly fields and forces in the center of each strand.
  • Margin to Jc-fit = TRUE triggers the calculation of the position of each block on the load line, that is, the position of that strand in the block that is exposed to the highest field. The margins are calculated by bisection w.r.t. the Jc-fit function that is specified in the .cadata file.
  • Margin to linear Jc-approx. = FALSE This option would calculate the margin w.r.t. to a linear approximation of the Jc-fit. This can be useful to speed up optimizations.
  • Enthalpy margins: This option triggers the calculation of enthalpy margins to quench, that is to say, we determine how much energy can be deposited in the coils to raise the temperature above the critical level. Three types of margins are calculated and printed to the output file:
    • Strand-wise: For very fast energy deposits heat conduction is negligible and the enthalpy margin to quench depends only on the heat capacity of the strand materials.
    • Cable-wise without helium: In the case of slower losses the temperature accross the conductor is assumed to be constant due to heat conduction.
    • Cable-wise with helium: If the voids in the cable are partially filled with helium, then the heat capacity differs largely from the cable without helium. How much of the voids is filled with helium needs to be specified by setting a design variable from the 'Quench thermal model' menu. QHELL is a number between 0 and 1, 1 denoting completely filled voids, and 0 completely empty voids. Default is 0. Note that in order to save time you can type the number once, e.g. in the Xs column, and type ctrl+shift+t to set the other two columns to the same value.
  • Block Restriction: This field is a list of those blocks, in which we want to calculate the fields, forces, and margins. No entry is equivalent to selecting all blocks. In our case we select only the two blocks in the first quadrant, since all other blocks feature equivalent data by symmetry. This option is meant to be a time saver in optimizations, as well as in peak field calulations in 3D.
  • Plotting 2D: We visualize the field and all of the above margins in the cross-section. Data is only available in the first two blocks, as defined in the Block Restriction.

Files

use_case_4.zip

  • peakFields.data
  • roxie.bhdata
  • roxie.cadata