Introduction

The Mitsubishi FR-E700 series Variable Frequency Drive (VFD), particularly the FR-E720 model, is renowned globally for its compact size, high quality, and cost-effectiveness. This makes it a popular choice for various industrial applications. In this guide, we will explore how to use the Siemens S7-1200 PLC, combined with the CB 1241 RS485 module, to control the FR-E720 inverter via Modbus-RTU communication.

This tutorial provides a detailed, step-by-step approach, from wiring connections to parameter configurations, ensuring you have all the necessary information to implement this setup effectively.

1. S7-1200 & FR-E720 Wiring Diagram

Before beginning the configuration, it is essential to establish the correct wiring connections between the Siemens S7-1200 PLC and the Mitsubishi FR-E720 VFD. The S7-1200 PLC uses the CB 1241 RS485 module for communication, which interfaces with the FR-E720’s Modbus-RTU communication port.

S7-1200 & FR-E720 Wiring Diagram

Key Wiring Points:

• Power Connections: Ensure that the VFD and PLC are correctly powered according to the manufacturer’s specifications.
• RS485 Communication: Properly connect the RS485 terminals on the CB 1241 module to the corresponding terminals on the FR-E720 VFD.
• Grounding: Ensure that all components are properly grounded to prevent electrical noise and ensure reliable communication.

2. FR-E720 Parameter Configuration

For the FR-E720 to communicate effectively via Modbus-RTU, certain parameters must be configured. Below is a list of essential parameters that need to be set on the FR-E720 inverter.

FR-E720 Modbus-RTU Communication Parameters:

1. Pr117: = 1 (Communication Mode Selection)
2. Pr118: = 3 (Baud Rate Selection)
3. Pr119: = 0 (Parity Bit Selection)
4. Pr120: = 2 (Stop Bit Selection)
5. Pr121: = 9999 (Communication Timeout Setting)
6. Pr122: = 9999 (Retry Count Setting)
7. Pr123: = 9999 (Checksum Error Setting)
8. Pr124: = 1 (Communication Start Bit)
9. Pr340: = 1 (Station Number Setting)
10. Pr549: = 1 (Communication Protocol Selection)
11. Pr79: = 2 (Last Setting Confirmation)

FR-E720 Parameter Configuration Table

These settings ensure that the FR-E720 VFD is correctly configured to communicate via Modbus-RTU, allowing the Siemens S7-1200 PLC to send and receive data.

3. Modbus Register Address Configuration

The FR-E720 VFD uses specific Modbus register addresses to control and monitor its operations. Below are the key register addresses required for basic control functions.

Modbus Register Addresses:

• Setting Frequency: 40014 (dec)
• Motor Control Address: 40009 (dec)

Control Commands:

• Forward Run: Set 40009 = 0000.0000.0000.0010 (Bin) = 2 (dec)
• Reverse Run: Set 40009 = 0000.0000.0000.0100 (Bin) = 4 (dec)
• Stop Command: Set 40009 = 0000.0000.0000.0000 (Bin) = 0 (dec)

Modbus Register Address Table

These register addresses and commands are fundamental for controlling the VFD’s operation, such as starting, stopping, and changing the direction of the motor.

4. Data Output Monitoring

For monitoring purposes, the Siemens S7-1200 PLC can read data from the FR-E720 VFD using Modbus registers. In this example, we will read three consecutive registers that contain essential operational data.

Monitoring Register Addresses:

• Starting Address: 40201 (dec)
• Length: 3 (bits)

Data Output Monitoring Configuration

This configuration allows the PLC to monitor critical parameters such as output frequency, current, and other operational metrics from the VFD.

5. Siemens S7-1200 PLC Configuration

To establish communication between the Siemens S7-1200 PLC and the FR-E720 VFD, the CB1241 RS485 module must be configured correctly. This section outlines the necessary steps for configuring the module and building the Modbus communication blocks.

Steps for Configuration:

• CB1241 RS485 Module Configuration:
  • Set up the communication parameters on the CB1241 to match those configured on the FR-E720 VFD.

Siemens S7-1200 PLC Configuration

• Modbus Block Construction:
• • Build Modbus communication blocks within the Siemens TIA Portal to manage the data exchange between the PLC and the VFD.

Siemens S7-1200 PLC Configuration

Proper configuration of the PLC and RS485 module ensures seamless communication with the VFD, allowing for effective control and monitoring.

6. S7-1200 PLC Programming

The final step involves programming the Siemens S7-1200 PLC to control the FR-E720 VFD. Below are the key programming elements required for successful VFD control.

Programming Steps:

• Distributing Transmission:
  • Set up the initial communication blocks to manage data transmission between the PLC and the VFD.

• Communication Load:
• • Ensure the PLC is continuously polling the VFD for status updates and control signals.

• Setting Frequency Command:
• • Write logic to send frequency setting commands to the VFD, allowing for speed control of the motor.

• Control Motor:
• • Implement logic to send start, stop, forward, and reverse commands to the VFD.

• VFD Status Feedback:
• • Program the PLC to receive and interpret feedback from the VFD, such as motor speed, current, and fault status.

These programming steps are essential for integrating the VFD control into your automation system, ensuring that the motor operates as required.

Conclusion

This comprehensive guide has walked you through the entire process of configuring and programming the Siemens S7-1200 PLC to control the Mitsubishi FR-E720 VFD via Modbus-RTU. By following these steps, you can achieve reliable and efficient control of the FR-E720, leveraging the power of Siemens automation technology in your industrial applications.

With this setup, you can easily integrate the FR-E720 VFD into a wide range of automation systems, ensuring optimal performance and control.