Morgensen MSI350 Series, User Manual, Page: 280 / 388

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V, the logic is "0".
The 485+ terminal on the terminal block of the inverter corresponds to A, and 485- corresponds to B.
The communication baud rate (P14.01) indicates the number of bits transmitted in a second, and the
unit is bit/s (bps). A higher baud rate indicates faster transmission and poorer anti-interference
capability. When a twisted pair of 0.56 mm (24 AWG) is used, the maximum transmission distance
varies according to the baud rate, as described in the following table.
Baud rate (bps)
Max. transmission
distance
Baud rate (bps)
Max. transmission
distance
2400 1800 m 9600 800 m
4800 1200 m 19200 600 m
When RS485 interfaces are used for long-distance communication, it is recommended that you use
shielded cables, and use the shield 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.
Therefore, it is recommended that you use a 120
Ω terminal resistor when the transmission distance
is long.
5. Application to one inverter
Fig 9.1 is the Modbus wiring diagram of one inverter 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 inverter, 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.
PC
Inverter
Ground A B
B
A
RS485 line
RS232-RS485 converter
Shielded twisted pair
Ground
485+ 485-
Fig 9.1 Wiring of RS485 applied to one inverter
6. Application to multiple inverters
In practical application to multiple inverters, chrysanthemum connection and star connection are