
B–62755EN/01
2. HARDWARE
127
The following ground systems are provided for the CNC machined tool:
1. Signal ground system (SG)
The signal ground (SG) supplies the reference voltage (0V ) of the
electrical signal system to the machine.
2. 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
and cases of the units, panels, and shields for the interface cables
between the units are connected.
3. System ground system
The system ground system is used to connect the frame ground
systems connected between devices or units with the ground.
Power
mag-
netics
unit
Servo
amplifi-
er
CNC
control
unit
Machine
tool
Operator’s
panel
Distribution board
Power magnet-
ics cabinet
Signal ground system
Frame ground system
System ground system
Notes on connecting the
ground systems
⋅ Connect the signal gournd with the frame ground (FG) at only one
place in the CNC control unit.
⋅ The grounding resistance of the system gorund shall be 100 ohms or
less (class 3 grounding).
⋅ The system ground cable must have enough cross–sectional area to
safely carry the accidental current flow into the system gound when
an accident such as a short circuit occurs.
(Generally, it must have the cross–sectional area of the AC power
cable or more.)
⋅ Use the cable containing the AC power wire and the system gound
wire so that power is supplied with the ground wire connected.
D Ground