Powering Field Equipment outside the Cabinet Section 3 Configuration
104 3BSE 027 941 R301
To avoid the AC 800M Controller being influenced by field equipment, it is strongly
recommended that separate power supplies be installed (see Figure 24 on page 88
and Figure 25 on page 89).
Sectioning the field equipment
If field equipment connected to an AC 800M Controller is to be sectioned into
groups – thus avoiding a power failure in one group from influencing the power to
other groups – then it is recommended to use separate power supplies for each field
equipment group.
The use of fuses in the 24 V DC distribution system is not a fail-safe measure. If a
short circuit occurs in one group, then voltage will most likely drop before a fuse
blows; consequently all groups will experience a drop in voltage.
Cable protection
24 V DC distribution system cables must be fuse-protected. In order to allow for
overload/short circuit situations, the power supply output current is limited. Allow
the power supply an extra capacity of at least 3-4 times the rated current value of the
largest connected fuse and remember to include long cable resistance in the
calculation.
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