Chapter 3 To Connect Power; Power Source; Power Cable Selection - COBHAM EXPLORER 325 Installation Manual

To connect power

3.1 Power source

The 12 or 24 V DC supply of the vehicle provides power for the terminal.
Do not use the cigarette lighter socket in the vehicle to supply power for the
Note
EXPLORER 325. Connect directly to the 12 or 24 V supply instead.
Note that the maximum allowed source impedance is much lower for a 12 V DC supply than
for a 24 V DC supply. Also, the total output power available for Power over Ethernet is limited
when the power supply is 12 V DC.
Be aware of high start-up peak current: 20 A at 24 V, 5 ms.
The terminal is equipped with an internal 20 A Fuse, so no external fuse is necessary in order to
protect the terminal. However, in order to avoid short circuit in the power cable/connector, the
DC outlet of the vehicle should be protected by a 30 A fuse or circuit breaker.

3.2 Power cable selection

3.2.1 Source impedance
The length of the power cable depends on the type of cable used and the source impedance of
the DC power installation in the vehicle.
The maximum allowed source impedance depends on the usage of the power range of the
terminal DC input (10.5 - 32 V DC; 11.5 A - 4 A).
Select a power outlet from the DC system and measure the source impedance of the
installation as described in the next section.
If the total impedance is higher than the limits stated in this section, the terminal
Note
may become unstable and start to on/off oscillate.
The total impedance is made up of the source impedance of the vehicle power
supply plus the impedance of connected cables including connectors and joints
where cables are extended.
For further recommendations on power cable selection, see Power cable recommendations
on page 15.
98-131306-B Power source
Chapter 3
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