Instruction Manual

Chapter 4 Installation and Wiring
4-13
4.2.3 Grounding
This section describes the precautions for grounding the ST unit.
• When supplying power to the ST unit, be sure to separate the
input/output and power lines, as shown. [diagram (a)]
• If exclusive grounding is not possible, use a common
grounding point. [diagram (b)] A D-type grounding or
equivalent should be used for the grounding point.
4.2.4 I/O Signal Line Placement
• Input and output signal lines must be separated from the power control cables for operating circuits.
• If this is not possible, use a shielded cable and connect the shield to the ST unit’s frame.
Do not use common grounding, since it can lead to an accident or machine breakdown.
• Check that the grounding resistance is
100Ω or less.
• FG and SG terminals are internally
connected in the ST. When connecting
an external device to the ST using the
SG terminal, be sure to check that no
short-circuit loop is created when you
setup the system.
• The grounding wire should have a
cross sectional area greater than
2mm
2
. Create the grounding point as
close to the ST unit as possible, and
make the wire as short as possible.
When using a long grounding wire,
replace the thin wire with a thicker wire,
and place it in a duct.
• If the equipment does not function properly
when grounded, disconnect the ground wire
from the FG terminal.
(a) Exclusive Grounding (BEST)
(b) Exclusive Grounding (OK)
(C) Common Grounding (Not OK)
ST
ST
Other
Equipment
ST
Other
Equipment
Other
Equipment