Design Of Frequency Conversion & Velocity Adjustment Elevator System Based On PLC

Along with the development of modern economy and city life, the elevator has become a essential walking tool for people in daily life, and the performance of elevators obviously influences people's lives. The traditional elevator system based on relay largely decreases the reliability and security since the mechanical and electromagnetic inertia of relay is big. In order to ensure the efficiency and reliable securities, the control method of elevator must be changed. The programmable logic controller(PLC), which develops based on sequence logical control, is digital operation electronic device specialized in the industrial application environment. PLC possesses fast process speed and high reliability. Therefore, PLC can be able to ensure the elevator run normally, securely and reliably. In addition, the drive method of elevators has replaced the DC velocity modulation with frequency control due to the development of AC frequency control of motors. The frequency control not only satisfies the comfort sense of passengers and ensures the stable precision, but also decreases the loss of power, saves resources and reduces expenses. The frequency control method based on PLC is applied to the elevator system and further researched.Firstly, the essay respectively presents the characteristics of the elevator system based on relay control and PLC control, specially formulates the defects exposed from relay control system and the advantages of PLC control system, introduces the frequency control of elevators. Secondly, based on reading many domestic and international relative literatures, the development of elevator techniques and elevator devices is overviewed. And then, the relative knowledge of frequency-converter is introduced; the principle of PLC model election and design scheme of PLC control system are introduced as well. On the basis of these, the PLC software of elevator system is developed according to the working states demands of the elevator. A elevator system based on PLC control is designed through combining the characteristics of software development and the rules of PLC control. Finally, the analog examination shows the elevator frequency control based on PLC possesses high operational efficiency and strong system security. The system structure is simple and easily realized, and satisfies the demands of the elevator system expected.