Difference between revisions of "Contact Physics – Formulas"
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*'''Constriction resistance''' | *'''Constriction resistance''' | ||
− | : | + | : <math>R_e = \rho/2a</math> |
(Single spot contact according to Holm; circular touching spot between clean | (Single spot contact according to Holm; circular touching spot between clean | ||
contact surfaces) | contact surfaces) | ||
− | : | + | : <math>R_e = \rho/2Na</math> |
(Multi-spot contact according to Holm without influence between the N | (Multi-spot contact according to Holm without influence between the N | ||
individual spots) | individual spots) | ||
− | : | + | : <math>R_e = \rho/2 x \sum a_i + 3 \pi \rho /32N^2 x \sum \sum (s_ij) i \neq j</math> |
(Multi-spot contact according to Greenwood considering the influence between | (Multi-spot contact according to Greenwood considering the influence between | ||
the spots) | the spots) | ||
*'''Contact resistance''' | *'''Contact resistance''' | ||
− | : | + | : <math>R_K = R_e + R_f</math> |
*'''Path resistance''' | *'''Path resistance''' | ||
− | : | + | : <math>R_d = R_b + R_K</math> |
*'''Contact resistance and contact force''' | *'''Contact resistance and contact force''' | ||
− | : | + | : <math>R_K = 280\rho \sqrt[3]{E (F_K \cdot r)} </math> |
(According to Holm model for film-free spherical contact surfaces with plastic | (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) | deformation of the contact material; F<sub>k</sub> < 1 N for typical contact materials) | ||
− | : | + | : <math>R_K = 9000 \rho \sqrt{ H/ F_K}</math> |
(According to Holm model for film-free spherical contact surfaces with plastic | (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) | 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) | *'''Dynamic contact separation''' (without considering magnetic fields caused by the current path) | ||
− | : | + | : <math>F_A \approx 0,8 xl^2</math> |
(Rule of thumb with F<sub>A</sub> in N and l in kA) | (Rule of thumb with F<sub>A</sub> in N and l in kA) | ||
*'''Contact voltage and max. contact temperature''' | *'''Contact voltage and max. contact temperature''' | ||
− | : | + | : <math>T_kmax \approx 3200 U_K</math> |
*'''Contact resistance at higher contact forces (according to Babikow)''' | *'''Contact resistance at higher contact forces (according to Babikow)''' | ||
− | : | + | : <math>R_K = cF_k^{-m}</math> |
For F<sub>K</sub> between 10 and 200 N<br/> | For F<sub>K</sub> between 10 and 200 N<br/> | ||
c = material dependent proportionality factor<br/> | c = material dependent proportionality factor<br/> |
Revision as of 12:33, 7 February 2019
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 |