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22 Guidelines for planning electrical installation
Defining the rating for the DC feeder unit
In the instructions below, the DC feeder unit rating is defined for a battery. The
instructions are also applicable to other energy storage types.
1.
Specify the continuous load current ( I
charging current ( I
I
_
= continuous load current of the DC feeder unit
n
bat
I
= load current of the DC feeder unit while charging the battery
C
I
= C × I
_
C
n
bat
C: C rating for the battery. Typical values: 0.7 / 1 / 2 / 3.
2.
Make sure that the nominal current ( I
continuous load current ( I
3.
For the DC feeder unit of frame size 2×ST or 3×ST (parallel strings of the DC feeder
unit), split the battery pack to equal parts. Observe that the nominal current I
each DC feeder string is higher or same as the continuous load current ( I
and the charging current ( I
unit string. You can connect several battery sections to one DC feeder unit string.
You must not connect a battery section to several DC feeder unit strings.
4.
For each DC feeder unit string: Define the short circuit current provided by the
battery connected to the string. Observe that the current does not exceed the
short circuit current rating. Refer to
5.
Observe that the sum short circuit current of the DC feeder unit strings does not
exceed the allowed maximum summary peak current for the DC feeder unit. Refer
to
Short circuit current ratings (page
6.
Make sure that the selected cables are protected by the DC feeder unit fuses
against a fault at the end of cable on the battery side.
If this is not the case, splitting the battery in smaller sections and connecting
those via DC feeder unit strings with lower current ratings can improve the
situation. The fuse rating changes according to the nominal current I
string.
7.
Make sure that the selected cables are protected by the battery fuses against a
fault at the end of the cable on the DC feeder unit side.
Equipping the DC feeder unit with a charging circuit
If you equip the DC feeder unit with a DC switch/disconnector (option +F290), it is
also possible to equip it with a charging circuit (option +F272) . The charging circuit
is intended for charging a capacitor. It is not intended for charging a battery.
The maximum capacitances for each DC feeder unit frame size are:
•
1×ST: 9 mF
•
2×ST: 18 mF
•
3×ST: 27 mF.
n
) for the battery.
C
n
_
) and the charging current ( I
n
bat
) of the battery section connected to that DC feeder
C
Short circuit current ratings (page
_
) of the DC feeder unit and the required
bat
) of the DC feeder unit is higher than the
60).
).
C
1
_
n
bat
60).
of each
1
of
)
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