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Precautions for Safe Use

NX-series CPU Unit Hardware User’s Manual (W535)

• Always connect to a ground of 100

Ω

or less when installing the Units.

• If the LG and GR terminals are connected, make sure to connect them firmly. The LG terminal that is

a noise-filtered neutral terminal, has a half electrical potential of the input voltage. Therefore, if you
touch the metallic part of the LG terminal, GR terminal, or Controller, while the GR terminal is not
grounded, it may result in electrical shock even when a normal operation is performed.

• Follow the instructions in this manual to correctly perform wiring.

Double-check all wiring and switch settings before turning ON the power supply.

• Use crimp terminals for wiring.

Do not connect bare stranded wires directly to terminals.

• Do not pull on the cables or bend the cables beyond their natural limit.

Do not place heavy objects on top of the cables or other wiring lines. Doing so may break the cables.

• Mount terminal blocks and connectors only after checking the mounting location carefully.
• Be sure that the terminal blocks, expansion cables, and other items with locking devices are properly

locked into place.

• Before you connect a computer to the CPU Unit, disconnect the power supply plug of the computer

from the AC outlet. Also, if the computer has an FG terminal, make the connections so that the FG
terminal has the same electrical potential as the GR terminal on the Power Supply Unit. A difference
in electrical potential between the computer and Controller may cause failure or malfunction.

• If the external power supply to an Output Unit or slave has polarity, connect it with the correct polarity.

If the polarity is reversed, current may flow in the reverse direction and damage the connected
devices regardless of the operation of the Controller.

• Do not exceed the rated supply capacity of the Power Supply Units in the NX-series Controller. The

rated supply capacities are given in the

NX-series CPU Unit Hardware User’s Manual

(Cat. No.

W535).
If the capacity is exceeded, operation may stop, malfunctions may occur, or data may not be backed
up normally for power interruptions.

• Do not apply voltages or connect loads to the Output Units or slaves in excess of the maximum rat-

ings.

• Surge current occurs when the power supply is turned ON. When selecting fuses or breakers for

external circuits, consider the above precaution and allow sufficient margin in shut-off performance.
Refer to the relevant manuals for surge current specifications. Refer to the

NX-series CPU Unit Hard-

ware User’s Manual

(Cat. No. W535) for surge current specifications.

• If the full dielectric strength voltage is applied or turned OFF using the switch on the tester, the gener-

ated impulse voltage may damage the Power Supply Unit. Use the adjustment on the tester to grad-
ually increase and decrease the voltage.

• Apply the voltage between the Power Supply Unit’s L1 or L2 terminal and the GR terminal when test-

ing insulation and dielectric strength.

• Do not supply AC power from an inverter or other device with a square-wave output. Internal tem-

perature rise may result in smoking or burning. Always input a sinusoidal wave with the frequency
that is given in the

NX-series CPU Unit Hardware User’s Manual

(Cat. No. W535).

• Install external breakers and take other safety measures against short-circuiting in external wiring.