Danfoss VLT AutomationDrive FC 300 Design Manual page 118

6. How to Install
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Illustration 6.45: Compact IP 21 (NEMA 1) and IP 54 (NEMA 12) enclosure E1
6.5.3. Earthing
The following basic issues need to be considered when installing a frequency converter, so as to obtain electromagnetic compatibility
(EMC).
• Safety earthing: Please note that the frequency converter has a high leakage current and must be earthed appropriately for safety reasons.
Apply local safety regulations.
• High-frequency earthing: Keep the earth wire connections as short as possible.
Connect the different earth systems at the lowest possible conductor impedance. The lowest possible conductor impedance is obtained by keeping the
conductor as short as possible and by using the greatest possible surface area.
The metal cabinets of the different devices are mounted on the cabinet rear plate using the lowest possible HF impedance. This avoids having different
HF voltages for the individual devices and avoids the risk of radio interference currents running in connection cables that may be used between the
devices. The radio interference will have been reduced.
In order to obtain a low HF impedance, use the fastening bolts of the devices as HF connection to the rear plate. It is necessary to remove insulating
paint or similar from the fastening points.
6.5.4. Extra Protection (RCD)
ELCB relays, multiple protective earthing or earthing can be used as extra protection, provided that local safety regulations are complied with.
In the case of an earth fault, a DC content may develop in the faulty current.
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MG.33.BA.02 - VLT ® is a registered Danfoss trademark
FC 300 Design Guide