EMC Basics
Capacitive Coupling Mechanism Capacitive coupling is a coupling via the electric field. It occurs between neighboring circuits - such as between high power current and signal lines. A fluctuating potential difference between the two circuits allows electrical current to flow through the insulation medium, air for example, that lies between them. The two lines that are lying next to one another can be considered as electrodes of a capacitor which is indicated by coupling capacity CK. Well known sources of interference are: Switching off power lines Inductivity switching Lightning discharges Electrostatic discharge The following circuit diagram shows the construction of capacitive coupling. Circuit 1 indicates a high power line for example and circuit 2 an analog measurement line. When the high power line is switched off, the potential difference between the two neighboring lines is changed. Interference current iK flows through the coupling capacity:
Character definitions: Character
Meaning
1
Circuit 1: Interference source (high power cable for example)
2
Circuit 2: Susceptible equipment with impedance Z2
CK
Coupling capacity
iK
Interference current flowing through the coupling capacity
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