General Rules for Dimensioning of Contacts
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) 0.05 - 0.08 N/A (Silver – Metal oxide contacts) Power switches 0.1 - 0.2 N/A Connectors > 30 cN/contact element (Gold coating) Connectors > 50 cN/contact element (Silver coating) Connectors > 1 N/contact element (Tin coating)
- 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
