Schneider M340 PLC and frequency converter guide - the Modbus communication

PLC through the Modbus to monitor the operation of the converter is one of the more common in industrial applications, this paper takes schneider M340 PLC controller and ATV71 inverter as an example, a brief introduction to the process of the Modbus serial communication between PLC and frequency converter, including the hardware connection, inverter parameter Settings, software configuration, such as electricity debugging, realize remote control on the PLC ATV71 converter fault initialization, start/stop, forward/reverse, a given frequency, etc.

1, M340 and ATV71 Modbus connection

only need a standard RJ45 twisted pair as the communication cable, end in a Modbus ATV71 communication port, the other end of the insert M340 CPU serial port, the connection is as follows:

2, M340 hardware configuration

double click on the CPU serial port, open to the Modbus Master configuration

configure a serial port for Modbus Master station, communication parameter setting in the Settings and ATV71 frequency converter, the following table:

set after clicking the confirm button to confirm.

3, program

according to the following instructions to define READ_VAR

after the input respectively in the steps of the 3-2-1 click OK to confirm the input, and inserted in the ladder diagram READ_VAR block

in the same way that you can enter WRITE_VAR block parameters is slightly different, that is as follows:

after the parameter Settings module inserted below:

time token: in order to realize the system scalability, allow with multiple frequency converter, and the best in each PLC controller scan cycle can have eight communication module ( READ_VAR / WRITE_VAR) Active in communication at the same time, to control multiple frequency converter, need to time-sharing control of frequency converter, set the time here is the token is in order to make multiple inverter turns communication description

variable

ladder diagram program

each converter has a unique time makes the brand, only in the current time token is equal to the time the token of the frequency converter, communication will be allowed to activate.

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