Toshiba NV Series Hardware Manual page 100

(3) Line filter ground (LG) terminal
The LG terminal is a neutral point of the line filter at the primary power supply.
Grounding the LG terminal is effective in reducing influence of common mode noise
on the power supply line.
Therefore, usually connect the LG terminal with a wire of 1mm
ground bar in the panel.
However, if the power supply is one-side grounding, there may be a problem of
leakage current flowing from the LG to the earth. If this is the case, put an isolated
transformer in the power supply or open the LG terminal.
If the controller unit is installed in isolation, open the LG terminal as well.
Avoid connecting the LG and FG terminals without grounding them.
Remarks
In migration from the T3 series, when using the terminal board of PS361 for BUM7B, there is no
LG terminal on BUM7B, and it is "NC", but there is no problem even if NC and FG are
short-circuited by the short bar.
(4) Frame ground (FG) terminal
This is the ground terminal of the controller unit. The base unit metal also has the
same potential as with the FG terminal.
To prevent electrification by static electricity and security/safety problems, ensure to
ground it at single point.
Unified Controller nv Series type1 light Controller Unit Operating Instructions
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