Basics: Cables and wires

The durability of the materials used in our cables and wires in the application environment, the correct installation and the loads applied within the scope of permissible limits (technical data) have a significant influence on the safety and lifespan of our cables. See the accompanying documentation or the warranted characteristics in special processes of our cables and wires for notices on applications and technical data.

The uses of cables and wires are especially diverse, and accordingly regulated by many application standards in various standardization circles (IEC, EN, NEC etc.). One example here is the international standard IEC 60204-1:2009, (Electrical equipment of machines - Part 1: General Requirements) relating to the requirements for cables and wires and their application conditions.

In each case, when satisfying these general requirements the user must check carefully to determine whether a specific product standard with different or further requirements exists that has higher priority.

Conductors, cables and wires must be selected such as to be suitable for the occurring operating conditions (e.g. voltage, current, electric shock protection, bundling of cables and wires) and for external influences (e.g. ambient temperature, presence of water or corrosive materials, mechanical stress including stresses while laying, or risk of fire). For cable developments, we will be happy to advise you on the functional scope and equipping of the cable.

The rated voltage is the reference voltage for which cables and wires are designed and tested. In an alternating current system, the rated voltage of cables and wires must be greater than or equal to the power supply’s rated voltage. In a direct current system, the system’s rated voltage must not be greater than 1.5 times the rated voltage of the wire. The operating voltage of AC and DC systems may continuously exceed their rated voltage by 10%.

The rated voltage of cables and wires is expressed as the ratio U/U0 in volts, where:

• U0 is the RMS (root mean square) voltage between the outer conductor and earth (metal sheathing/shielding of the wire or surrounding medium)
  
• U is the RMS voltage between two outer conductors of a multi-core wire or a system of single-core wires
  

The dielectric strength of conductor, cable and wire insulation must be able to withstand the required test voltage. For cables and wires operated at voltages above 50 V AC or above 120 V DC, the test voltage is at least 2000 V AC for a duration of 5 minutes. For AC voltages of max. 50 V and DC voltages of max. 120 V (typically SELV or PELV systems), the test voltage must be at least 500 V AC for a duration of 5 minutes.

You must know these important principles for using and laying cables. From your cable manufacturer Scherer Kabel.