General Rules for Dimensioning of Contacts

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6.4.6 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

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  • 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)

Fig. 6.18: Failure probability of a contact as a function of the voltage (according to Kirchdorfer); Ag/Ni10; 10 mA

Fig. 6.19: 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