Goodrive20-UL Series VFD
Communication protocol
-114-
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
–+6V, it is logic "1", if the electrical level is among
-2V
–-6V; 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 is, the quicker the transmission speed is and the weaker the
anti-interference is. If the twisted pairs of 0.56mm (24AWG) is applied as the communication
cables, the Max. Transmission distance is as below:
Baud
rate
Max.
transmission
distance
Baud
rate
Max.
transmission
distance
Baud
rate
Max.
transmission
distance
Baud
rate
Max.
transmission
distance
2400
BPS
1800m
4800
BPS
1200m
9600
BPS
800m
19200
BPS
600m
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 120
Ω terminal
resistor as the performance will be weakened if the distance increase even though the network
can perform well without load resistor.
7.2.1.1 When one VFD is used
Figure 7-1 is the site Modbus connection figure of single VFD 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 VFD 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 VFD.
Summary of Contents for GD20-0R4G-2-UL
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