Toshiba Vm Series Instruction Manual page 48

Chapter1 On Installing typeS Controller
(2) Ground wiring between bases
(3) Line filter ground (LG) terminal
(4) Frame ground (FG) terminal
30
6F8C1645
On-board ground bus
Dedicated D class ground for the control device
Figure.1.16.
 Connect the FG terminal and the base fixing screw of the power module, and wire
the panel in the shortest distance to the in-panel grounding bus with 2mm
wire (recommend).
 Separate the control unit grounding from the grounding cable of the high voltage
circuit, as class D grounding.
The LG terminal is the neutral point of the primary power line filter. Grounding the LG
terminal can affect to reducing effects of common mode noises in the power line.
Therefore, connect the LG terminal to the grounding bus in the panel with a wire of
2mm 2 or more(recommended). However, if the power supply is a single-sided
grounding system, leakage current will flow from LG to ground, and causes a
problem. In such a case, insert an insulation transformer in the power supply or open
the LG terminal. Also open the LG terminal when the controller unit is insulated.
Avoid connecting LG and FG without grounding LG and FG.
This is the grounding terminal of the controller unit. The base unit metal part is also
the same electric potential as that of the FG terminal.
Be sure to ground them at a single point to prevent static electricity, and for security
and safety reasons.
Controller unit
Power
supply
FG
Base unit
FG FG
I/O unit I/O unit
Ground wiring between bases
FG
I/O unit
2 or more