Instruction manual

2. Preparation for Installation
54
(4) Requirements for the incoming current to the distribution board
The capacity of the incoming current to the distribution board must be greater than
that of the breaker operating current described in the above (3) Distribution board.
Ensure that the capacity for incoming current to the distribution board
is greater than the operating current of the circuit breaker. If it is not,
the circuit breaker might not operate properly in the event of a failure,
which could result in fire.
NOTE
Generally, the breaker operating current is greater than the rated
current. Check the specifications of the circuit breaker.
In addition, when a Switch is turned on, inrush current shown in the figure below
flows. Consider measures for avoiding a voltage drop in the power supply facility
caused by the inrush current.
Table 2-9 Inrush current
Current Time
30 A 150 ms
CAUTION
When a Switch is turned on, inrush current flows. Consider measures
for avoiding a voltage drop in the power supply facility caused by the
inrush current. Voltage drops affect not only the Switch, but also the
devices connected to the same power supply facility.
NOTE
The inrush current described above is the value for a single power
supply unit.
2.4.3 Power supply facility for −48 V DC
(1) DC power cable
When using a Switch in a −48 V DC environment, use only the power cable
described in Table 2-10 DC power cable specifications.
Use the termi
nals described in Figure 2-8 0 V and −48 V terminals as the 0 V an
d
−48 V terminals of a DC power cable, and use either terminal described in Figure
2-9 Ground terminal as th
e ground terminal.
For information about the distances from the cable clamp to the 0 V terminal, the
-48 V terminal, and the ground terminal, see Figure 2-10 Terminal board of the DC
power suppl
y unit.
Table 2-10 DC power cable specifications
Cable specifications Power supply unit
Number of cores AWG No.
External diameter
of the cable
PS-D11 Three cores 4 30 to 32 mm