Delta MS300 Series User Manual page 16

Isolating main power from ground:
When the power distribution system for the drive is a floating ground system (IT Systems) or an
asymmetric ground system (Corner Grounded TN Systems), you must remove the RFI jumper.
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, you

must properly ground the motor and drive during installation.
 The diameter of the grounding cables must comply with the local safety regulations.
 You must connect the shielded cable to the motor drive's ground to meet safety regulations.
 Only use the shielded cable as the ground for equipment when the aforementioned points are met.
 When installing multiple drives, do not connect the grounds of the drives in series but connect each
drive to ground. The following pictures show the correct and wrong ways to connect the grounds.
Pay particular attention to the following points:
 Do not remove the RFI jumper while the power is on.
 Removing the RFI jumper also cuts the capacitor conductivity of the surge absorber to ground and
the built-in EMC filter capacitors. Compliance with the EMC specifications is no longer guaranteed.
 Do not remove the RFI jumper if the mains power is a symmetrical grounded power system in order
to maintain the efficiency for EMC circuit.
 Remove the RFI jumper when conducting high voltage tests. When conducting a high voltage test
to the entire facility, disconnect the mains power and the motor 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.
 Remove the RFI jumper to disconnect the ground cable from the internal filter capacitor and surge
absorber.
 Do not install an external RFI/EMC filter. The external EMC filter passes through a filter capacitor
and connects power input to the ground. This is very dangerous and damages the motor drive.
In situations where EMC is required, use an EMC filter specifically for IT system if necessary.

Disconnecting the ground cable from the filter prevents damage to the motor drive but compliance
with EMC is no longer guaranteed.
 In situations where EMC is required, check for excess electromagnetic radiation affecting nearby
low-voltage circuits. In some situations, the adapter and cable naturally provide enough
Figure 1-7
7
Chapter 1 IntroductionMS300
Figure 1-8