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→6.4.2 Contact Physics – Formulas
===6.4.2 Contact Physics – Formulas===
*'''Constriction resistance''' <br />Re R<sub>e</sub> = D/2a
(Single spot contact according to Holm; circular touching spot between clean
contact surfaces)
(Multi-spot contact according to Holm without influence between the N
individual spots)
(Multi-spot contact according to Greenwood considering the influence between
the spots)
*'''Contact resistance and contact force''' <br />R<sub>K</sub> = 280D ³ E(F · r) K
(According to Holm model for film-free spherical contact surfaces with plastic
deformation of the contact material; F <sub>k</sub> < 1 N for typical contact materials) kRK R<sub>K</sub> = 9000 D H/ FK
(According to Holm model for film-free spherical contact surfaces with plastic
deformation of the contact material; F <sub>k</sub> > 5 N for typical contact materials)
*'''Dynamic contact separation''' (without considering magnetic fields caused by the current path) <br />FA F<sub>A</sub> 0,8 x I²I<sup>2</sup>(Rule of thumb with F <sub>A</sub> in N and I in kA)
*'''Contact voltage and max. contact temperature''' <br />T <sub>kmax </sub> 3200 UKU<sub>K</sub>
*'''Contact resistance at higher contact forces (according to Babikow)''' <br />R <sub>K</sub> = cF -m K K
For F between 10 and 200 N K
c = material dependent proportionality factor
