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Omron CP1H “Modbus RTU” Danfoss FC51 Tutorial

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Danfoss 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.

However, it also supports 1 RS485 port for convenient control by Modbus-RTU Communication. Today will guide you to use the Omron CP1H PLC to control it.

Omron CP1H & Danfoss FC51 “Connection Diagram”

The Omron CP1H PLC does not have an RS485 port available, so we must use an additional expansion module CP1W-CIF11 (or CP1W-CIF12).

Danfoss FC51 Modbus-RTU Configuration

In addition to the basic parameters of the inverter (Frequency, voltage, current…) we need to install the following parameters so that the inverter can be controlled by Modbus RTU

Registers for Control
  • VFD Control Address = C34F (hex)

+ Set Register C34F = 1148 (dec) >>> Forward Run
= 33916 (dec) >>> Reverse Run
= 1084 (dec) >>> Stop
= 1212 (dec) >>> VFD Reset

  • VFD Frequency Setting Address = C359 (dec)
    >>> Reference Setting = 0 to 16384(dec) ~ (0 to 100%)
Registers for Monitoring
Note: Danfoss FC302 Monitoring Address
= “(Table Address*10) – 1

+ Voltage Output Address = 16119 (dec)

+ Frequency Output Address = 16129 (dec)

+ Current Output Address = 16139 (dec)

Omron CP1H Modbus RTU Setting

In order for Omron CP1H to control Danfoss FC51 with Modbus-RTU, we need to set the communication parameters of CP1H to be the same as Danfoss FC51.

PLC Programming

+ Reset Control when Restart PLC

+ Transmission Distribution

+ Frequency Reference Command

+ VFD Control Command

+ VFD Data Monitoring

Detailed Instruction Video


Related Software and Documents

+ PLC Omron Programming Software Download

+ Danfoss FC51 Manual PDF Download (Password Extract:

Please share the article to the community if you find it useful. If you need any help in connecting Omron CP1H with Danfoss FC51, please comment below the article, will reply to you as soon as I read the comment.

Best Regards!

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  • Good afternoon, congratulations for the great tutorial. I don’t understand how to find modbus addresses in Danfoss documentation.
    How did you find these addresses (forward = 1148; reverse = 33916; stop = 1084; Frequency Output Read = #3F01?
    Please help me understand this?

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