Difference between revisions of "Contact Physics – Formulas"
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==References== | ==References== | ||
[[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]] | [[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]] | ||
Revision as of 12:35, 1 April 2014
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
![R_K = 280\rho \sqrt[3]{E (F_K \cdot r)}](/matheasy/bda0b56c91fccaa4c9a75816e15c1815.svg)
(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 |
