Contact Physics – Formulas
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
- Path resistance
- 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)
(Rule of thumb with FA in N and l in kA)
- Contact voltage and max. contact temperature
- Contact resistance at higher contact forces (according to Babikow)
For FK between 10 and 200 N
c = material dependent proportionality factor
m = shape dependent exponent of the contact force
Material combination | c |
---|---|
Copper - Copper | (0.08 bis 0.14) x 10-3 |
Aluminum - Aluminum | (3 bis 6,7) x 10-3 |
Brass - Brass | 0.67 x 10-3 |
Steel – Silver | 0.06 x 10-3 |
Steel – Copper | 3.1 x 10-3 |
Steel – Brass | 3.0 x 10-3 |
Contact shapes | m |
---|---|
Flat – Flat | 1 |
Pyramid – Flat | 0.5 |
Sphere – Flat | 0.6 |
Sphere – Sphere | 0.5 |
Multi-strand brush - Flat | 1 |
Current bar (Busbar) contact | 0.5 - 0.7 |