General Rules for Dimensioning of Contacts

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General Rules for Dimensioning of Contacts

  • Recommended Minimum Contact Forces at Slightly Sliding Contact Make:
Gold 0.03 N
Silver 0.1 N
Tungsten 0.5 N
  • Contact Force Recommendations:
Signal relays ≥ 3 cN
AC power relays ≥ 20 cN
Automotive relays ≥ 20 cN
Motor switches (Contactors)
(Silver – Metal oxide contacts)
0.05 - 0.08 N/A
Power switches 0.1 - 0.2 N/A
Connectors
(Gold coating)
≥ 30 cN/contact element
Connectors
(Silver coating)
≥ 50 cN/contact element
Connectors
(Tin coating)
≥ 1 N/contact element


  • General Rules for Dimensioning of Contact Rivets
General Rules for Dimensioning of Contact Rivets
Dimensioning Solid Rivets (1) Composite Rivets (2)
a : d 1.5 : 1 bis 2.5 : 1 2 : 1 bis 2.5 : 1
a : b 2.5 : 1 bis 10 : 1 3 : 1 bis 5 : 1
c : b ≥ 1 : 1 ≥ 1 : 1
b : s ≥ 2 : 1
smin ≈ 0.3 mm


  • Head diameter for electrical loads
For AC currents: approx. 1 – 1.5 A/mm²
For 1 A min. 2 mm head diameter
10 A approx. 3 – 3.5 mm head diameter
20 A approx. 5 mm head diameter
For DC currents: approx. 0.5 – 0.8 A/mm²


  • Head radius R for electrical loads
for I < 1 A R ≈ 1,5 mm
I = 6 A R ≈ 5 mm
I = 10 A R ≈ 10 mm
I = 20 A R ≈ 15 mm


  • Failure Probability of Single and Double (Bifurcated) Contacts (according to Thielecke)
Contact force[N] Single contact
Ag AuNi 5, Pt Ag AuNi 5, Pt
0.04 1 x 10-4 2 x 10-8
0.1 2 x 10-3 4 x 10-5 8 x 10-5 8 x 10-9
0.2 1 x 10-4 8 x 10-6 4 x 10-6 4 x 10-8
0.3 5.5 x 10-6 1.5 x 10-6 1.8 x 10-7 3.2 x 10-10


Failure probability of a contact as a function of the voltage (according to Kirchdorfer); Ag/Ni10; 10 mA
Failure probability of a contact as a function of the current (according to Kirchdorfer); Ag/Ni10; Fk = 0.45 N; U = 24 V

Figure 1 Failure probability of a contact as a function of the voltage (according to Kirchdorfer); Ag/Ni10; 10 mA

Figure 2 Failure probability of a contact as a function of the current (according to Kirchdorfer); Ag/Ni10; F = 0.45 N; U = 24 V

References

References