Hitachi HSC-2100, Руководство по оборудованию

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1 GENERAL INFORMATION
1-11
(4) Output modules
For each output module, connect a fuse to the power supply to the load for protection against
load short-circuit. The connected fuse must be one that matches the ratings of the load. If
a non-matching fuse is connected, the printed wiring board or casing used may be damaged
when the load is short-circuited.
(5) Grounding points
Each grounding terminal of the programmable controller must be grounded separately from
any other grounding terminals by using Class D grounding or higher (*). The grounding
terminal of an AC panel for distribution, in particular, must be grounded at least 15 meters
away from the grounding points of the aforementioned grounding terminals.
The best way to ground such grounding terminals is to weld the grounding cable from each
grounding terminal to the steel framework of the building (see the figure below). If such
welding cannot be accomplished, bury a grounding bar in the earth and ground the grounding
terminal through the bar.
(*) Class D grounding is defined in the Technical Standard for Electrical Facilities of Japan.
This standard states that the grounding resistance must be 100 ohms or less for
equipment operating on 300 VAC or less, and 500 ohms or less for devices that shut
down automatically within 0.5 seconds when shorting occurs in low tension lines.
Digital
output module
Fuse
Power
supply
Load
Programmable
controller
cubicle
Line grounding (LG)
Frame grounding (FG)
Steel
framework
AC panel
The grounding point for the
programmable controller cubicle
must be at least 15 meters away
from that for the AC panel.