6.4.2 Contact Physics – Formulas
- Constriction resistance
(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
RK = Re + Rf
- Path resistance
Rd = Rb + RK
- Contact resistance and contact force
(According to Holm model for film-free spherical contact surfaces with plastic deformation of the contact material; Fk < 1 N for typical contact materials) (According to Holm model for film-free spherical contact surfaces with plastic deformation of the contact material; Fk > 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 FA in N and I in kA)
- Contact voltage and max. contact temperature
Tkmax 3200 UK
- Contact resistance at higher contact forces (according to Babikow)
RK = cF -m K
For FK between 10 and 200 N c = material dependent proportionality factor m = shape dependent exponent of the contact force