A-6
What follows is noise prevention measures for the inverter drive configuration.
(1) Wiring and grounding
As shown in Figure A.7, separate the main circuit wiring from control circuit wiring as far as possible
regardless of being located inside or outside the system control panel containing an inverter. Use shielded
wires and twisted shielded wires that will block out extraneous noises, and minimize the wiring distance.
Also avoid bundled wiring of the main circuit and control circuit or parallel wiring.
Figure A.7 Separate Wiring
For the main circuit wiring, use a metal conduit pipe and connect its wires to the ground to prevent noise
propagation (refer to Figure A.8).
The shield (braided wire) of a shielded wire should be securely connected to the base (common) side of the
signal line at only one point to avoid the loop formation resulting from a multi-point connection (refer to
Figure A.9).
The grounding is effective not only to reduce the risk of electrical shocks due to leakage current, but also
to block noise penetration and radiation. Corresponding to the main circuit voltage, the grounding work
should be No. 3 grounding work (300 VAC or less) and special No. 3 grounding work (300 to 600 VAC).
Each ground wire is to be provided with its own ground or separately wired to a grounding point.
Figure A.8 Grounding of Metal Conduit Pipe Figure A.9 Treatment of Braided Wire of
Shielded Wire
(2) Control panel
The system control panel containing an inverter is generally made of metal, which can shield noise
radiated from the inverter itself.
When installing other electronic devices such as a programmable logic controller in the same control panel,
be careful with the layout of each device. If necessary, arrange shield plates between the inverter and
peripheral devices.
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