Electrically Conductive Connections
1. Function of Electrically Conductive Connections
Electrically conductive screw connections are specialized electrical connections designed to withstand mechanical stress while also conducting electricity. A characteristic feature of such applications is that insulating layers, such as paint or oxide layers, must be overcome during transfer of current.
Electrically conductive connections are used for transfer of current in low-resistance applications for earthing and equipotential bonding purposes.
A typical example of such an application is an earthing screw connection on a painted control cabinet sheet metal panel.
2. Current Status of Standardization for Electrically Conductive Connections and Design
The design of electrically conductive connections is not clearly regulated by standards. In principle, the number of components used—and thus the number of interface surfaces—should be minimized to counteract settlement effects. At the same time, the overall design must incorporate a spring-like effect to counteract settlement, creeping, and relaxation effects. The design recommended here is as described in the trade journal EP (Elektro-Praktiker) or by Rittal.
3. Recommendations for Earthing and Equipotential Bonding Screw Connections
- The number of components—and thus the number of interface surfaces—should be minimized to reduce settlement effects.
- The use of effective spring-loaded screw locking elements (lock washers or NSK-E or NSK-EL) is recommended in many standards and is beneficial for compensating for creeping, embedding, and relaxation effects.
- Electrical contact glands should also be secured against self-acting loosening by rotation.
- Regulatory framework: There are no uniform standards for the design of electrical contact glands.
- Practical recommendation: Technical publications such as *Elektropraktiker* (EP) or manufacturer recommendations (e.g., Rittal) provide proven assembly concepts.
4. Product recommendations (when insulating layers must be penetrated to establish electrical conductivity)
Contact discs in general. The NSK K contact washer is a multifunctional screw lock that facilitates current flow through its six prongs and additionally offers optimal residual spring characteristics due to its NSK shape, as well as anti-loosening properties thanks to its tried-and-tested coding system.