Contact Physics – Formulas
6.4.2 Contact Physics – Formulas
- Constriction resistance
Re = D/2a
(Single spot contact according to Holm; circular touching spot between clean contact surfaces) Re = D/2Na (Multi-spot contact according to Holm without influence between the N individual spots) Re = D/2 x E ai + 3B D/32N² x E E (sij) i = j (Multi-spot contact according to Greenwood considering the influence between the spots)
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- Contact resistance
RK = Re + Rf
- Path resistance
Rd = Rb + RK
- Contact resistance and contact force
R = 280D ³ E(F · r) K K
(According to Holm model for film-free spherical contact surfaces with plastic deformation of the contact material; F < 1 N for typical contact materials) k RK = 9000 D H/ FK (According to Holm model for film-free spherical contact surfaces with plastic deformation of the contact material; F > 5 N for typical contact materials)
- Dynamic contact separation (without considering magnetic fields caused by the current path)
FA 0,8 x I²(Rule of thumb with F in N and I in kA)
- Contact voltage and max. contact temperature
T kmax 3200 UK
- Contact resistance at higher contact forces (according to Babikow)
R = cF -m K K
For F between 10 and 200 N K c = material dependent proportionality factor m = shape dependent exponent of the contact force
