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MicroLogix 1400 “Modbus RTU” Danfoss FC51 Tutorial

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Danfoss VLT® Micro Drive FC 51 inverter is a popular inverter series, very compact in size, suitable for all common applications such as pumps, fans, conveyors, cooling towers, … the maximum capacity is 22kw, the biggest advantage of this inverter line is its low cost.

Although the price is cheap, Danfoss FC51 has quite good quality and fully supports the basic control types of the inverter. Today will guide you to use PLC MicroLogix 1400 to control Danfoss FC51 through Modbus RTU (RS485)

MicroLogix 1400 & Danfoss FC51 “Wiring Diagram”

+ Both Danfoss FC51 and MicroLogix have built-in RS485 Ports

+ Module 1763-NC01 for MicroLogix 1400 can be used for easy wiring
(If you don’t have it, you can connect it directly to the RS485 port of the PLC)

Danfoss FC51 “Modbus RTU” Configuration

In order for the Danfoss FC51 inverter to be controlled via Modbus-RTU, in addition to the basic parameters we need to install additional communication parameters as shown in the table below

Danfoss FC51 Registers Address for Control
Note: MicroLogix 1400 Address = “VFD Address (Dec) + 1

>>> VFD Control Address = 49999 + 1 = 50000 (dec)

  • Set Register 50000 = 1148 (dec) >>> Forward Run
    = 33916 (dec) >>> Reverse Run
    = 1084 (dec) >>> Stop
    = 1212 (dec) >>> VFD Reset

>>> VFD Frequency Setting Address = 50009 + 1 = 50010 (dec)

  • Speed Reference Setting: (0 to 16384) = (0 to 100%)
Danfoss FC51 Registers Address for Monitoring
  • Output Voltage Address = 16120 (dec)
  • Output Frequency Address = 16130 (dec)
  • Output Current Address = 16140 (dec)

MicroLogix 1400 “Modbus RTU” Setting Parameters

We need to set the same communication parameters between PLC MicroLogix 1400 and Danfoss FC51 VFD

MicroLogix 1400 “PLC Programming”

+ Read/Write Automatic Distribution

+ VFD Control Command

+ VFD Write Frequency Command

+ VFD Data Monitoring

Project Video Tutorial

Below is a video on setting parameters for Danfoss FC51 inverter and testing the program with real inverter and motor.


Required Documentation

+ Allen-Bradley MicroLogix 1400 Manual PDF Download
+ Danfoss FC51 Modbus RTU Manual PDF Download

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So has finished instructing you to use MicroLogix PLC to control Danfoss FC51 VFD through “Modbus RTU”, if you have any questions, please comment below the article, will reply as soon as I read comments.

Best Regards!

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