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3.3.8 Protective Earth
The earth connection serves several purposes.
•
Safety earth (Protective earth, PE)
The equipment must be properly earthed according to local regulation. This equipment has a leakage current > 3.5 mA AC. It must be connected
to an earth connection complying with the local rules for high leakage current equipment.
Typically, this implies that the PE conductors must be mechanically enhanced (minimum cross section 10 mm
2
) or duplicated
•
Noise “clamping” (high frequencies)
Stable communication between units call for screening of the communication cables (1). Cables must be properly attached to screen clamps
provided for that purpose.
•
Equalisation of voltage potential (low frequencies)
To reduce alignment currents in the screen of the communication cable, always apply a short earthing cable between units that are connected
to the same communication cable (2) or connect to an earthed frame (3).
•
Potential equalization: All metal parts, where the motors are fastened, must be potential equalized
PE connections, voltage equalising cables and the screen of the communication cable should be connected to the same potential (4).
Keep the conductor as short as possible and use the greatest possible surface area.
The numbering refers to the figure.
Illustration 3.5: Proper installation earthing
3 Installation
VLT
®
Decentral FCD 300 Design Guide
42
MG.90.S1.02 - VLT
®
is a registered Danfoss trademark
3