Grounding The Devicenet Communications Unit; Communications Power Supply Noise Prevention; Communications Cable Shielding - Omron 3G3MV-PDRT2 User Manual

Setup and Wiring

Grounding the DeviceNet Communications Unit

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The DeviceNet Communications Unit should be grounded according to DeviceNet recommendations
installing a noise filter as shown in the following diagram. The ground is normally wired to the ground
terminal ( ).
Note If the cable grounded to the Inverter is not sufficient and is receiving noise interference, discon-
nect the grounding cable.

3-3-3 Communications Power Supply Noise Prevention

The communications power supply is the most important power supply in a DeviceNet Network. The
following measures will prevent noise in the communications power supply.
• Use the recommended power supply (S82H/S82J) made by OMRON for communications.
• Use an independent power supply for communications.
• Make sure to install a noise filter on the primary AC input side of the communications power supply.
• Always use a control system power supply for the primary AC side of the communications power
supply that is not shared with power devices, such as Inverters or motors.
If noise interference remains in cables for which noise countermeasures have been implemented, the
following countermeasures may be effective.
●

Communications Cable Shielding

Suspend the communications cable shielding wire without grounding it. This will filter the noise that
flows from the ground to the communications cable and will filter the noise current that flows in the
shielding wire.
● Communications Power Supply
Suspend the communications power supply without grounding it. This will also filter the noise that
flows from the communications power supply ground to the communications cable or the noise cur-
rent that flows in the shielding wire. The switching power supply is usually connected to the case and
the capacitor as shown below. The ground (FG) terminal must be suspended and the control panel
for the power supply itself must be insulated.
Shield
Chapter 3
3-21