Difference between revisions of "Contact Physics – Formulas"

From Electrical Contacts
Jump to: navigation, search
(→‎6.4.2 Contact Physics – Formulas)
(12 intermediate revisions by 3 users not shown)
Line 1: Line 1:
−
===<!--6.4.2-->Contact Physics – Formulas===
+
===6.4.2 Contact Physics – Formulas===
  
 
*'''Constriction resistance'''  
 
*'''Constriction resistance'''  
Line 40: Line 40:
  
  
−
{| class="twocolortable scalable" style="text-align: left; font-size: 12px; width:45%;"
+
{| class="twocolortable" style="text-align: left; font-size: 12px"
 
|-
 
|-
 
!Material combination  
 
!Material combination  
Line 63: Line 63:
 
|3.0 x 10<sup>-3</sup>
 
|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 Guideline Data for Use of Electrical Contact Design#References|References]]
 
[[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]]
−
 
−
[[de:Formeln_aus_der_Kontaktphysik]]
 

Revision as of 12:03, 1 April 2014

6.4.2 Contact Physics – Formulas

  • Constriction resistance
R_e = \rho/2a

(Single spot contact according to Holm; circular touching spot between clean contact surfaces)

R_e = \rho/2Na

(Multi-spot contact according to Holm without influence between the N individual spots)

R_e = \rho/2 x \sum a_i + 3 \pi \rho /32N^2 x \sum \sum (s_ij) i \neq j

(Multi-spot contact according to Greenwood considering the influence between the spots)

  • Contact resistance
R_K = R_e + R_f
  • Path resistance
R_d = R_b + R_K
  • Contact resistance and contact force
R_K = 280\rho \sqrt[3]{E (F_K \cdot r)}

(According to Holm model for film-free spherical contact surfaces with plastic deformation of the contact material; Fk < 1 N for typical contact materials)

R_K = 9000 \rho \sqrt{ H/ F_K}

(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)
F_A \approx 0,8 xl^2

(Rule of thumb with FA in N and l in kA)

  • Contact voltage and max. contact temperature
T_kmax \approx 3200 U_K
  • Contact resistance at higher contact forces (according to Babikow)
R_K = cF_k^{-m}

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

References

References

Retrieved from "https://www.electrical-contacts-wiki.com/index.php?title=Contact_Physics_–_Formulas&oldid=2749"