Industrial Communication Guide

COMPONENTS AND STRUCTURE OF AUTOMATION SYSTEMS

of the cable. Typical materials include plastics such as TPE, PUR and PVC.

Wire insulation Wire insulation serves to protect the electrical conductor so as to avoid short circuits, for fixing purposes and to provide protection from contact. The plastics used for insulation have negligible elec- trical conductivity, low water absorption capability, high thermal resilience and high abrasion resistance. Frequently used insulation materials are: PVC, PE, PP, PTFE, rubber and PUR. Shielding At high frequencies, the wires of a cable act like antennas. This means that they emit electromagnetic fields into the environment (e.g. nearby electrical cables), and also absorb electromagnetic fields from the environment. In order to reduce this influence on the environment and on data transmission, the cables are fitted with electrical protection. Typical shielding types and materials include braided shields made of copper wires (mainly coated with tin) and foil shields made of aluminum or copper. While braided shields protect the line primarily against low-frequency interference, foil screens provide protection against high-frequency interference. Cable sheath The cable sheath protects the inner cable structure from chemical impact (acids, alkalies, oils), mechanical stress (abrasion, torsion) and environmental impact (UV radiation). The correct choice of sheath material is therefore essential to the durability and resilience

Criteria for selecting a cable Cables have to be selected in such a way that they are suited to the relevant operating conditions and external influences. The following criteria have to be considered when making the choice: • What is the required purpose: Is the cable to be used for energy transmission or signal transmission? • In which industrial sector is it to be used? (certifications, approv- als) • By means of which components is the cable to be connected? (energy or signal transmission, connection technology) • In which temperature range is the cable to be used? Will the con- nection be exposed to changes in temperature during operation? (electrical conductivity, operating conductivity) • Is the cable to be stationary or non-stationary? (flexibility of the cable) • How is the cable to be installed? (laying method, flexibility, con- nection technology) • In which environment is the cable to be used? (chemical resist- ance, resistance to water and dampness, combustibility, protec- tion from UV radiation)

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