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Note If the cable grounded to the Inverter is not sufficient and is receiving noise interference, discon-
nect the grounding cable.
Shield
2-4-3 Communications Power Supply Noise Prevention
The communications power supply is the most important power supply in a CompoBus/D Network. The
following measures will prevent noise in the communications power supply.
• Use the recommended power supply (S82H/S82J) 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 sup-
ply 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.
D 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.
D 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 current that
flows in the shielding wire. The switching power supply is usually connected to the case and the capaci-
tor as shown below. The ground (FG) terminal must be suspended and the control panel for the power
supply itself must be insulated.
Switching Power Supply Configuration
Switching power supply
AC power supply AC input
Casing
DC output
Power
supply
circuit
CompoBus/D Communications Line Design Chapter 2