Emerson PACMotion VFD Series User Manual page 77

Figure 31: RS-485 Communications Electrical Connections
Connection to the
drive through the
option
OPT-2-BNTSP-IN
Modbus
RTU RS485
Controller
RS485+
RS485-
0 Volt / Common
Ground
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.
GFK-3111A
Direct connection to the drive
through the built-in RJ45 port
RJ45 connector pinout
1 2 3
Pin 3 – 0 Volt / Common
Pin 7 – RS485- (Modbus RTU)
Pin 8 – RS485+ (Modbus RTU)
PACMotion VFD AC Variable Speed Drive User Guide
NOTES
• Use 3 or 4 Conductor Twisted
• RS485+ and RS485- must be
• Ensure the network taps for the drive
1 2 3 4 5 6 7 8
• Terminate the network cable shield at
1 2 3 4
5 6 7 8
• 0 Volt common must be connected
• Do not connect the 0V Common
RS485+
RS485-
0 Volt / Common
Shield
Pair Cable
twisted pair
are kept as short as possible
the controller only. Do not terminate
at the drive!
across all devices and to reference
0 Volt terminal at the controller
of the network to power ground
77