Difference between revisions of "Contact Physics – Formulas"

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(→‎6.4.2 Contact Physics – Formulas)
(→‎6.4.2 Contact Physics – Formulas)
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|Brass - Brass  
 
|Brass - Brass  
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|0,67 x 10<sup>-3</sup>
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|0.67 x 10<sup>-3</sup>
 
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|Steel – Silver
 
|Steel – Silver
 
|0.06 x 10<sup>-3</sup>
 
|0.06 x 10<sup>-3</sup>
 
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|-
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|ASTM B 36/B36M-95 || Spec. for Brass Plate, Sheet, Strip, and Rolled Bar
+
|Steel – Copper
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|-
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|3.1 x 10<sup>-3</sup>
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|ASTM B 122/B122M-08 || Spec. for CuNiSn-, CuNiZn-, and CuNi-Alloy
 
−
|-
 
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|ASTM B 465-09 || Spec. for Copper-Iron-Alloy Plate, Sheet, and Strip
 
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|ASTM B 194-08 || Standard Spec. for CuBe-Alloy Plate, Sheet, Strip and Rolled Bar
 
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|ASTM B 534-07 || Sec. for CuCoBe-Alloy and CuNiBe-Alloy Plate, Sheet, Strip, and Rolled Bar
 
 
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|Steel – Brass
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|3.0 x 10<sup>-3</sup>
 
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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 12:03, 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

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