EMC Measures
EMC Measures for Grounding Systems EMC functions of the grounding system The grounding system has the following tasks with regard to EMC: Interference current dissipation Prevent couplings Maintaining shielding at specific potentials The grounding system must fulfill these requirements without interfereing with the device and wiring. NOTE: Green-yellow equipment grounding conductors are not usually suitable for these tasks. Grounding conductors can only dissipate low-frequency signals (50 ...60 Hz), and do not guarantee equipotential bonding for high-frequency signals as their impedance is too high. Effect of grounding The galvanic coupling is affected by the ground connection. Disturbances can spread via the grounding system across the entire plant if the grounding system is poorly configured or bad connections are made. EMC measures for grounding systems The following EMC arrangements are available for grounding systems: Optimal selection and combination of grounding systems (point-to-point or meshed) if necessary Meshed grounding: sufficiently small surface area of the loop between exposed conductive parts Sufficient cross-section of the earth conductors low-resistance and low-inductance lines and therefore an effective equipotential bonding for low and high frequency signals Good chassis connection to decrease the contact resistance Types of grounding systems Two types of grounding systems are used: S Type: Point-to-point M Type: Grid-type Large plants use both grounding types in combination as they have varying effectiveness depending on the application. The advantages and disadvantages of each system are described below.
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