GFK-3111A PACMotion VFD AC Variable Speed Drive User Guide 77
Figure 31: RS-485 Communications Electrical Connections
Modbus
RTU RS485
Controller
RS485+
RS485-
0 Volt / Common
Ground
NOTES
• Use 3 or 4 Conductor Twisted
Pair Cable
•RS485+ and RS485- must be
twisted pair
• Ensure the network taps for the drive
are kept as short as possible
•Terminate the network cable shield at
the controller only. Do not terminate
at
the drive!
•
0 Volt common must be connected
across all devices and to reference
0 Volt terminal at the controller
• Do not connect the 0V Common
of the network to power ground
OPT-2-BNTSP- IN
12 3
RS485+
0 Volt / Common
Connection to the
drive through the
option
RS485-
Pin 3 –
0 Volt / Common
Pin 7 – RS485- (Modbus RTU)
Pin 8 – RS485+ (Modbus RTU)
RJ45 connector pinout
Direct connection to the drive
through the built-in RJ45 port
1 2 3 4 5 6 7 8
1
2
3
4
5
6
7
8
RS485+
RS485-
0 Volt / Common
Shield
Modbus RTU and CANbus connection should be made via the RJ45 connector. The pin assignments are as
shown above, in section RS-485 Communications.
• Modbus RTU and CANbus networks require three conductors for best operation and to eliminate
common mode voltages on the drive terminals:
o RS485+
o RS485-
o 0 Volt Common
• Connection should be made using a suitable dual twisted pair, shielded cable, with a wave impedance of
120 Ohms.
• Use one of the twisted pairs to connect to the RS485+ and RS485- of each drive.
• Use one conductor of the remaining pair to connect together all the 0 volt common connection
terminals.
• The cable shield should be connected to a suitable clean ground point to prevent interference with the
screen maintained as close as possible to the cable terminations.
• Do not connect the 0 Volt Common, RS485- or RS485+ to ground at any point.
• Network terminating resistor (120 Ohms) should be used at the end of the network to reduce noise.
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