ABB UNITROL 1020 - Page 44

Chapter 3 - Device Overview 
36 3BHS335648 E82 UNITROL 1020 User Manual
RH RL RS
CG
CH CL
-
+
-
+
485
gnd
CAN
X1300
RS-485
X1302
CAN
Shielding
should be
grounded.
Max.
30 mm
CV CS
5V Shield
RS
CH
RH RL CV
CLCS CG
Figure 3-5 Shielding and wiring recommendation when using the RS-485 interface.
The signal line shield must be connected only at one location to PE, typically at the end
of the line.
RS485 for VDC and remote access
When configuring the RS485 interface for VDC or remote access, a jumper bridge must
be placed over the X1300 terminals of each AVR located at the end of the bus; and it
should be removed from those not located at the end (see Figure 3-6). No resistor should
be placed externally, i.e. on the device's terminals, when the jumper bridge of the
UN1020 is already being used.
RL
RS
RH 1
2
RS-485
AVR 1
RL
RS
RH1
2
AVR 2
+
-
1
2
RS-485
RL
RS
RH1
2
AVR 3
1
2
RS-485
RL
RS
RH1
2
AVR 4
+
-
X1300
X1300
X1300X1300
Figure 3-6 RS-485 wiring and jumper settings to use VDC on a set of four AVRs.
As shown in Figure 3-6 the topology of the bus should be as "one line" with two endings,
and not as a "star". The recommendations described in Chapter 3.3.9.3 RS485 Interface
should be strictly followed. The VDC feature operates only over RS485 and could not
work properly if there is any other device incompatibly connected to the same bus.
The VDC software should be configured in each device prior to use. The configuration is
described in Chapter 3.4.3.1 Voltage Droop Compensation (VDC).
3.3.9.4 CAN Interface
A CAN interface is provided for both Double Channel (connection with a second channel)
and UN1000-PM; however both cannot use the bus simultaneously. As will be explained
in Chapter 3.4.4.4 - Double Channel (DCH), the DCH Supervision can be used together
with a UN1000-PM connected to the AVR since the CAN communication is not needed
for the operation of the monitoring functions. However, the remaining functions from
Double Channel are not compatible with the UN1000-PM. For more information see
Chapter 3.4.4.4.9 - DCH Communication: Configuration and Compatibility.