Goodrive350A series high-performance multifunction VFD
Communication
-316-
Baud rate (bps)
Max. transmission
distance
(meter)
Baud rate (bps)
Max. transmission
distance (meter)
2400BPS
1800m
9600BPS
800m
4800BPS
1200m
19200BPS
600m
When RS485 interfaces are used for long-distance communication, it is recommended that you use
shielded cables, and use the shielding layer as the ground wires.
When there are fewer devices and the transmission distance is short, the whole network works well
without terminal load resistors. The performance, however, degrades as the distance increases.
Ther
efore, it is recommended that you use a 120Ω terminal resistor when the transmission distance is
long.
9.3.1.1 When one VFD is used
Figure 9.1 is the Modbus wiring diagram for the network with one VFD and PC. Generally, PCs do not
provide RS485 interfaces, and therefore you need to convert an RS232 or USB interface of a PC to
an RS485 interface through a converter. Then, connect end A of the RS485 interface to the 485+ port
on the terminal block of the VFD, and connect end B to the 485- port. It is recommended that you use
shielded twisted pairs. When an RS232-RS485 converter is used, the cable used to connect the
RS232 interface of the PC and the converter cannot be longer than 15 m. Use a short cable when
possible. It is recommended that you insert the converter directly into the PC. Similarly, when a
USB-RS485 converter is used, use a short cable when possible.
When the wiring is completed, select the correct port (for example, COM1 to connect to the
RS232-RS485 converter) for the upper computer of the PC, and keep the settings of basic
parameters such as communication baud rate and data check bit consistent with those of the VFD.
Computer
VFD
Ground
A
B
B
A
RS485 line
RS232-RS485 converter
Shielded twisted pair
Ground
485+
485-
Figure 9.1 RS485 wiring diagram for the network with one VFD
9.3.1.2 When multiple VFDs are used
In the network with multiple VFDs, chrysanthemum connection and star connection are commonly
used.
According to the requirements of the RS485 industrial bus standards, all the devices need to be
connected in chrysanthemum mode with one 120
Ω terminal resistor on each end, as shown in Figure
9.2. Figure 9.3 is the simplified wiring diagram, and Figure 9.4 is the practical application diagram.