Hello friends!
Siemens S7-200 PLC and Danfoss FC51 inverter are two extremely popular devices on the market, although they have been around for a long time, they are still trusted by many engineers today.
Today thelivingchristmascompany.com will guide you to use Siemens S7-200 PLC to control Danfoss FC51 through Modbus-RTU communication protocol in the simplest and easiest way to understand.

Siemens S7-200 & Danfoss FC51 “Wiring Diagram”
Both Siemens S7-200 and Danfoss-FC51 have built-in RS485 communication ports, so we can connect them according to the diagram below to serve Modbus-RTU communication.

Danfoss FC51 Modbus Parameters Setting
Below are the Modbus communication parameters that we need to install for the Danfoss FC51 inverter:

Danfoss FC51 Registers Address Mapping


Note: Siemens S7-200 Holding Registers Address =
“VFD Address (Dec) + 400001”
>>> VFD Control Address= 49999 + 400001 = 450000 (dec)
- Set Word 49999 = 1148 (dec) >>> Run Forward
- Set Word 49999 = 33916 (dec) >>> Run Reverse
- Set Word 49999 = 1084 (dec) >>> Stop
- Set Word 49999 = 1212 (dec) >>> VFD Reset
>>> VFD Frequency Setting Address = 50009 + 400001= 450010 (dec)
- Reference Setting = 0 to 16384(dec) ~ (0 to 100%)
>>> Output Voltage Address = 16129 + 400001 = 416120 (dec)
>>> Output Frequency Address = 16139 + 400001 = 416130 (dec)
>>> Output Current Address = 16139 + 400001 = 416140 (dec)
Siemens S7-200 Modbus Example
+ Read / Write Distribution

+ Port.0 Modbus Configuration

+ VFD Frequency Setting

+ VFD Control Command

+ VFD Data Monitoring

Video Tutorial
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References
+ Siemens STEP7 MicroWin V4.0 SP9 Download
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Best Regards!