Isolating Main Power From Ground; Floating Ground System (It Systems) - Delta MS300 Series User Manual

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Isolating main power from ground:

When the power distribution system of the drive is a floating ground system (IT) or an asymmetric ground
system (TN), the RFI Jumper must be removed. Removing the RFI Jumper disconnects the internal
capacitors from ground to avoid damaging the internal circuits and to reduce the ground leakage current.
Important points regarding ground connection
 To ensure the safety of personnel, proper operation, and to reduce electromagnetic radiation, the
drive must be properly grounded during installation.
 The diameter of the cables must comply with the local safety regulations.
 The shield of shielded cables must be connected to the ground of the drive to meet safety regulations.
 The shield of shielded power cables can only be used as the ground for equipment when the
aforementioned points are met.
 When installing more drives, do not connect the grounds of the drives in series but connect each drive
to ground.
Pay particular attention to the following points:
 Do not remove the RFI jumper while the power is on.
 Removing the RFI jumper will also disconnect the built-in EMC filter capacitors. Compliance with the
EMC specifications is no longer guaranteed.
 The RFI jumper may not be removed if the mains power is a grounded power system.
 The RFI jumper may not be removed while conducting high voltage tests. When conducting a high
voltage test to the entire facility, the mains power and the motor must be disconnected if the leakage
current is too high.

Floating Ground System (IT Systems)

A floating ground system is also called an IT system, an ungrounded system, or a high
impedance/resistance (greater than 30 Ω) grounded system.
Disconnect the RFI Jumper.

Check whether there is excess electromagnetic radiation affecting nearby low-voltage circuits.

In some situations, the transformer and cable naturally provide enough suppression. If in doubt, install

an extra electrostatic shielded cable on the power supply side between the main circuit and the control
terminals to increase security.
Do not install an external EMC filter. The EMC filter is connected to ground through the filter

capacitors, thus connecting power input to ground. This is very dangerous and can easily damage the
drive.
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