Using PLC and frequency converter to realize motor speed regulation, we must first understand that the frequency converter is the one to realize the speed regulation function, and PLC only controls the frequency converter to realize this function, so we only need to control PLC and then control the frequency converter to realize speed regulation. There are the following methods:

1. Use 4-20mA or 0- 10V in the analog input of the frequency converter to change the frequency, that is to say, connect the analog output of PLC to the analog input of the frequency converter, so as to control the PLC to change the frequency.

2. Use communication methods. At present, most PLC and frequency converters support 485, Ethernet or other communication modes. Then communicate with the frequency converter through PLC, and control the frequency of the frequency converter through programming and exchanging data.