Thrane&Thrane SAILOR 6110, Installation Manual

Page: 45 / 82

Chapter 4: Connecting the system
Connecting power 35
4444
Co
n
n
ec
ti
ng t
h
e
sy
st
em
At the point where the extension cable is to be connected, measure the source
impedance as described in
Measuring the ship source impedance on page 37.
The total impedance is made up of the source impedance of the power supply
plus the impedance of connected cables including connectors and joints
where cables are extended.
Calculating the maximum power cable extension
For 15 V DC operation
(which is used in the GMDSS system), the total
impedance must be max. 800 m

, including the source impedance in the ship
installation.
The total impedance is made up of the following:
• the source impedance in the ship installation
• the cable impedance of the supplied power cables, including the
impedance in the joint of the two cables. In the following example, the
measured source impedance includes the impedance of the supplied
cables.
• the extension cable impedance.
To calculate the maximum cable extension, do as follows:
1. First measure the source impedance in the ship installation, including
supplied cables, as shown in Measuring the ship source impedance on
page 37.
2. Then find the resistance per meter for the cable type you are going to use.
The table below shows typical cable resistance - note that your cable type
may differ from this. Refer to the data sheet for the cable you are using.
Note
If the total impedance is higher than the limits stated in the
beginning of the next section, the system may become unstable.
Cross section (mm
2
) 0.5 1 1.31
(AWG 16) 1.5 2 2.5
Resistance (m

/m) 32.2 16.1 13 10.7 8.05 6.76