Difference between revisions of "Contact Physics – Formulas"
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− | ===6.4.2 Contact Physics – Formulas=== | + | ===<!--6.4.2-->Contact Physics – Formulas=== |
− | *'''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''' | |
− | + | : <math>R_K = R_e + R_f</math> | |
− | |||
− | *'''Contact resistance''' < | ||
− | *'''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 < 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 > 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) | ||
+ | : <math>F_A \approx 0,8 xl^2</math> | ||
+ | (Rule of thumb with F<sub>A</sub> in N and l in kA) | ||
− | *''' | + | *'''Contact voltage and max. contact temperature''' |
+ | : <math>T_kmax \approx 3200 U_K</math> | ||
− | + | *'''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/> | ||
+ | c = material dependent proportionality factor<br/> | ||
+ | m = shape dependent exponent of the contact force | ||
− | |||
− | + | {| class="twocolortable scalable" style="text-align: left; font-size: 12px; width:45%;" | |
− | + | |- | |
− | + | !Material combination | |
− | + | !c | |
− | m = | + | |- |
+ | |Copper - Copper | ||
+ | |(0.08 bis 0.14) x 10<sup>-3</sup> | ||
+ | |- | ||
+ | |Aluminum - Aluminum | ||
+ | |(3 bis 6,7) x 10<sup>-3</sup> | ||
+ | |- | ||
+ | |Brass - Brass | ||
+ | |0.67 x 10<sup>-3</sup> | ||
+ | |- | ||
+ | |Steel – Silver | ||
+ | |0.06 x 10<sup>-3</sup> | ||
+ | |- | ||
+ | |Steel – Copper | ||
+ | |3.1 x 10<sup>-3</sup> | ||
+ | |- | ||
+ | |Steel – Brass | ||
+ | |3.0 x 10<sup>-3</sup> | ||
+ | |} | ||
+ | |||
+ | {| class="twocolortable scalable" style="text-align: left; font-size: 12px; width:45%; " | ||
+ | |- | ||
+ | !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 | ||
+ | |} | ||
+ | <div class="clear"></div> | ||
==References== | ==References== | ||
− | [[Application Tables and | + | [[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]] |
+ | |||
+ | [[de:Formeln_aus_der_Kontaktphysik]] |
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 |