ABB ACS255 - Compatibility with IT (Ungrounded) and Corner-Grounded TN Systems

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5.4. Compatibility with IT (ungrounded) and corner-grounded TN systems
WARNING! EMC filters should not be used when installing the drive on an IT system (an ungrounded
power system or high-resistance-grounded power system, otherwise the system will be connected to
ground potential through the EMC capacitors. This may cause danger or damage to the EMC filter.
If you have an IT (ungrounded) system or corner-grounded TN system, disconnect the internal Varistor
screw as shown below.