7-2
The 3G3MV Inverter has standard RS-422/485 and optional DeviceNet communica-
tions functions. This section provides information on how to communicate over
RS-422/485. For DeviceNet communications in detail, refer to the 3G3MV-PDRT2 Devi-
ceNet Communications Unit/Card User’s Manual (I539).
It is possible to control the Inverter, give frequency references, monitor the Inverter sta-
tus, and read and write parameters through communications.
A maximum of 32 Inverter Units can be connected to RS422/485 communications and
used as a simple network system.
Note The RS-422/485 communications of the 3G3MV Inverter conform to the MOD-
BUS Communications Protocol and this protocol cannot be used together with
any other communications protocol. Only 3G3MV-Series products can be con-
nected as Slaves. If a DeviceNet Communications Unit is used, RS-422/485 com-
munications will not be possible. Therefore, select which communications method
is to be used.
(The MODBUS Communications Protocol is a trademark of AEG Schneider
Automation.)
7-1 Inverter Settings
7-1-1 Setting the Communications Conditions
H Communications Time-over Detection Selection (n151)
• This parameter is used for monitoring the communications system.
• The set value in the parameter determines whether communications time-over detection will be per-
formed with “CE” displayed if there is an interval of more than 2 s between normal communications.
The method to process the detected communications time-over is also determined according to the
set value in the parameter.
• When a control signal (the RUN command, forward/reverse rotation command, or an external fault
signal) is input into the Inverter through communications, be sure to set n151 to 0, 1, or 2. Then the
system will stop in the case of a time-over detection.
If there is a communications failure, no control input will be operable. It will be, however, impossible to
stop the Inverter if n151 is to 4 or 3.
Use a host program that monitors how the Inverter handles all control input signals, for example, so
that there will be no interval of more than 2 s between communications.
n151
RS-422/485 Communications
Time-over Detection Selection
Register 0197 Hex Changes during
operation
No
Setting
range
0 to 4 Unit of
setting
1 Default setting 0
Communications Chapter 7
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