
B–65192EN/02
7. INSTALLATION CONDITIONS
AND CAUTIONS
39
The following ground systems are provided for CNC machine tool.
(a) Signal ground system (SG)
The signal ground (SG) supplies the refernce voltage (0V) of the
electrical signal system.
(b) Frame ground system (FG)
The frame ground system (FG) is used for safety, and suppressing
external and internal noises. In the frame ground system, the frames,
cases of the units, panels, and shields for the interface cables between
the units are connected.
(c) System ground system
The system ground system is used to connect the frame ground
systems connected between devices or units with the ground.
Other
units
Servo
amplifier
CNC
System ground system
Signal ground system
Frame ground system
Shield
Operation
panel
Machine
Cabinet
Distribution board
WARNING ON CONNECTING THE GROUND SYSTEMS
D The gounding resistance of the system ground shall be 100
ohms or less (class 3 grounding).
D The system ground cable must have enough cross–
sectional area to safely carry the accidental current flow into
the system ground when an accident such as a short circuit
occurs. (Generally, it must have the cross– sectional area
of the AC power cable or more.)
D Use the cable containing the AC power wire and the system
ground wire so that power is supplied with the ground wire
connected. See Sec. 5.3 for details when a power
transformer for an export is used.
7.3.2
Ground