INVT Goodrive 35 Series Operation Manual page 213

Goodrive35 inverters
which is called balance transmission, too. It uses twisted pairs, one of which is defined as A (+) and
the other is defined as B (-). Generally, if the positive electrical level between sending drive A and B is
among +2 – +6 V, it is logic"1", if the electrical level is among -2 V – -6 V, it is logic"0".
485+ on the terminal board corresponds to A and 485- to B.
Communication baud rate means the binary bit number in one second. The unit is bit/s (bps). The higher
the baud rate, the quicker the transmission speed and the weaker the anti-interference. If twisted pair of
0.56mm (24AWG) is used as communication cable, the max transmission distance is as below:
Baud rate Max transmission distance
2400BPS
4800BPS
It is recommended to use shield cables and make the shield layer as the grounding wires during
RS485 remote communication.
In the cases with less devices and shorter distance, it is recommended to use 120Ω terminal resistor
as the performance will be weakened if the distance increases even if the network can perform well
without load resistor.
10.3.1.1 Single application
Figure 1 is the site Modbus connection figure of single inverter and PC. Generally, the computer does
not have RS485 interface, the RS232 or USB interface of the computer should be converted into
RS485 by converter. Connect the A terminal of RS485 to the 485+ terminal of the inverter and B to the
485- terminal. It is recommended to use the shield twisted pairs. When applying RS232-RS485
converter, if the RS232 interface of the computer is connected to the RS232 interface of the converter,
the wire length should be as short as possible within the length of 15m. It is recommended to connect
the RS232-RS485 converter to the computer directly. If using USB-RS485 converter, the wire should
be as short as possible, too.
Select a right interface to the upper monitor of the computer (select the interface of RS232-RS485
converter, such as COM1) after the wiring and set the basic parameters such as communication baud
rate and digital check bit to the same as the inverter.
1800m
1200m
Fig 10-1 RS485 physical connection in single application
Baud rate Max transmission distance
9600BPS
19200BPS
206
Communication protocol
800m
600m