Glossary · Electrical engineering and control panels
Shielding
Also known as: Screening, Cable shielding
German: Schirmung
In electrical engineering, shielding is the use of conductive layers, such as cable braids, foils or enclosures, to reduce the coupling of electromagnetic fields into or out of cables and equipment.
- Control panels
In one sentence
Shielding uses conductive braids, foils or enclosures to reduce electromagnetic coupling into or out of cables and equipment.
Example
The motor cable of the frequency converter is shielded, and the shield is clamped over its full circumference at the cabinet entry and at the motor terminal box.
How it applies
- Engineering: Shield effectiveness depends on the connection: low-impedance, full-circumference contact (for example with EMC clamps or glands) works far better than twisted "pigtails". Whether to ground at one or both ends depends on frequency range, cable type and the quality of equipotential bonding.
- Installation: Shields must be continuous through connectors and terminals. Separating power and signal cables complements shielding.
- Documentation: Specify cable types with shields in cable lists and describe shield connection with drawings or photos in installation manuals. Many EMC problems in the field trace back to shield connections described only vaguely.
Shielding vs. protective earth
A shield reduces electromagnetic interference. The Protective earth (PE) conductor protects people from electric shock. A cable shield must not replace a protective conductor.