GBK60027 DX-SLM Installation Manual Issue 5
DX modules normally have one or two DX BUS sockets for system interconnections.
Smaller DX modules may have a permanently mounted cable terminated in a DX BUS
plug, rather than DX sockets.
The star and mixed topologies both require the use of one or more DX BUS Expanders
(DX-SKT-X3). The DX-SKT-X3 may be purchased from Dynamic Controls or a Dealer.
For lowest cost and simplicity the in-line topology is generally preferred, provided the
DX BUS length and voltage drop requirements described below can be met.
Warning:
If the SLM is between the Power Module and the Battery Charger:
1.
Have as few as possible DX BUS cables between the SLM and the Power
Module.
2.
The DX BUS cables between the SLM and the Power Module must not
total more than 1 metre.
This will avoid unintended interaction between the SLM and the Battery
Charger.
5.3.3
DX BUS Length and Voltage Drop Restrictions
Due to signal distortion that increases with increasing DX BUS length, the total length
of all DX BUS cables must not exceed 15 metres in any topology.
Two of the DX BUS's four cores (DXB+ and DXB-) are used to supply power to the
modules and to the loads connected to them. A Positive Temperature Coefficient
(PTC) device in the Power Module limits the total DX BUS current to 12 A, this protects
the DX BUS wiring and connectors. The topology and cable lengths used may reduce
the DX BUS's upper limit to below 12 A.
For correct DX System operation the voltage drop on the DX BUS's DXB- wire due to
return currents, must not exceed 1.0 V between any two modules within the DX
System. Use a topology and module placement that reduces this voltage drop as low
as reasonably possible.
Voltage drops occur along the DX BUS due to the return of current to the battery
through the small but finite resistance of the DX BUS cable and connectors.
A DX BUS connector can be modelled as:
DX BUS Cable Model
R
ct
= contact resistance
= 5 mOhm
R
ca
= cable resistance (B-) = 8.5 mOhm / metre
R
c
t
R
c
t
R
c
a (B-)
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T
