Goodrive270 series VFD for fan and pump Communication protocol
-294-
Max. transmission
distance
Max. transmission
distance
In long-distance RS485 communication, it is recommended that you use shielded cables, and use the
shielding layer as the ground wire.
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.
Therefore, it is recommended that you use a 120 Ω terminal resistor when the transmission distance
is long.
9.3.1.1 Application to one VFD
Figure 9-1 is the Modbus wiring diagram of one VFD and a PC. Generally, PCs do not provide RS485
interfaces, so you need to convert an RS232 interface or USB port of a PC to an RS485 interface.
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.
After wiring, select the correct port (such as COM1 to connect the RS232-RS485 converter) on the
upper computer, and set the basic parameters such as baud rate and data bit check consistent with
those of the VFD.
PC
VFD
GroundA B
B
A
RS485 line
RS232-RS485 converter
Shielded twisted pair
Ground
485- 485+
Figure 9-1 Wiring of one RS485 VFD application
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