Difference between revisions of "Contact Physics – Formulas"

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(Replaced content with "{| |'''Editor''': |DODUCO Holding GmbH<br> Im Altgefäll 12<br> 75181 Pforzheim / Germany<br> Phone +49 (0) 7231 602-0<br> Fax +49 (0) 7231 602-398<br> Mail: inf...")
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===<!--6.4.2-->Contact Physics – Formulas===
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{|
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|'''Editor''':
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|DODUCO Holding GmbH<br>
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Im Altgefäll 12<br>
  
*'''Constriction resistance'''
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75181 Pforzheim / Germany<br>
: <math>R_e = \rho/2a</math>
 
(Single spot contact according to Holm; circular touching spot between clean
 
contact surfaces)
 
: <math>R_e = \rho/2Na</math>
 
(Multi-spot contact according to Holm without influence between the N
 
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
 
the spots)
 
  
*'''Contact resistance'''
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Phone +49 (0) 7231 602-0<br>
: <math>R_K = R_e + R_f</math>
 
  
*'''Path resistance'''
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Fax +49 (0) 7231 602-398<br>
: <math>R_d = R_b + R_K</math>
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*'''Contact resistance and contact force'''
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Mail: info@doduco.net<br>
: <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
 
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
 
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
 
|-
 
|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==
 
[[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]]
 
 
 
[[de:Formeln_aus_der_Kontaktphysik]]
 

Latest revision as of 11:37, 7 February 2019

Editor: DODUCO Holding GmbH

Im Altgefäll 12

75181 Pforzheim / Germany

Phone +49 (0) 7231 602-0

Fax +49 (0) 7231 602-398


Mail: info@doduco.net