6-3SectionEmergency Stop
52
6-1 Grounding
The
Line
Ground (LG) terminal is a noise-filtered neutral terminal that does not
normally
require grounding. If electrical noise is a problem, however
, this termi
-
nal should be connected to the Ground (GR) terminal.
To
avoid electrical shock, attach a grounded (earth ground) AWG 14 wire (cross-
sectional
area of at least 2 mm
2
) to the GR terminal. The resistance to ground
must
be
less than 100
W
. Do not use a wire longer than 20 m. Care must be tak
-
en, because ground resistance is af
fected by environmental conditions such as
soil composition, water content, time of year, and the length of time since the
wire was laid underground.
PC
operation may be adversely af
fected if the ground wire is shared with other
equipment,
or if the ground wire is attached to the metal structure of a building.
When
using an Expansion I/O Rack, the Rack must also be grounded to the GR
terminal. The same ground can be used for all connections.
6-2 Insulation
If
a separate ground is being supplied to dif
ferent Racks, Insulating Plates must
be
used to insulate the Racks from each other
. Insulating Plates are supplied
as
an accessory (refer to
Appendix B Specifications
).
6-3 Emergency Stop
An
external relay should be used to form an emergency stop circuit that turns the
power
to the PC OFF in the event of an emergency
. An
emergency stop routine
in
the PC program is not suf
ficient to ensure safety
. The circuit shown below is an
example of an emergency stop circuit.
MCB1
Power
section
Control section
CR1
MCB2
PC RUN
output
CR1
PC
DC
input/output
Surge
suppressor
Twisted
Transformer
or
noise
filter
+
-
DC voltage
regulator
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