摘要：In order to realize multi-speed control of motor, a control system based on S7-1200 PLC and Siemens MicroMaster420 frequency converter is designed. Through the analysis of the cooling fan control requirements, the hardware system and software programming of the whole control system are designed. The PLC control unit of the control system completes signal acquisition, logic control and communication, etc. The system sets the parameters of the converter by changing the on-off state of the converter digital input, and further realizes the steering change and speed adjustment of the motor. Through experimental comparison, it is concluded that the control system designed in this paper can save more than 30% of the electric energy. The load of the motor is greater, and the energy-saving effect is more obvious. The advantages of the control system are simple circuit structure and convenient operation. The designed control system is simple and effective to realize the multi-stage control of the motor and improve the reliability and stability of the motor.
