Alternating Freight Elevators Controlling Based On PLC

In the wake of utilization in computer technology and the development and improvement of solid power device, elevator controlling technology has become modern technology since the first half of the 20th century, which is constant current speed regulation to alternating current varying frequency speed regulation. As introducing international standard and advanced products and technologies from developed countries, freight elevators as a kind of elevators have been developed and improved in our country.This paper the first chapter introduces the origin and the development of the elevator and the characteristics of the freight elevator with the present situation, and the design of the objectives, contents and significance.Chapter II first gives the definition, types, composition, which hopes to have a preliminary understanding of the lift. This chapter mainly introduces dragging and controlling technology, which frequency conversion and alternating current driving technology is applied in this paper. Elevator control technologies, including the relay control technology and the alternating-current VFVV control technology. Relay control technology in functions regards the PLC control as the equivalent circuit made of many "soft Relays". Frequency conversion and alternating current control technology introduces PWM and SPWM control technology which has one polar and two- polar nature of the two kinds. VVVF elevator is used asynchronous motors, whose power uses advanced technology and SPWM and SVPWM technologies, improving the quality and performance of operations.The third chapter describes the PLC's stage of development, definition, the basic structure and working principle, performance and features, PLC's application and selection, describing the basic composition of the inverter, classification, the vector control principle of the inverter and VVVF elevator control features. The design of the freight elevator control system is the system with random logic control. In addition the chapter also introduces the principle of PLC and hardware design of the VVVF freight elevator.Chapter 4 introduces the VVVF freight elevator'software program designation. It includes the main indicators of running the freight elevator control, and signal's input and layout, action requirements the in-outside controlling buttons in freight elevator cars. In addition, the chapter also adds progressing chart of controlling program and the design of Program of Ladder Diagram.Chapter 5 covers the monitor system and communications of the freight elevator. The communications include the choice of communication protocols and serial communications in two parts. The monitor system explains the need for monitoring, the monitoring characteristics, composition and function of the monitoring system. Finally, the monitoring software and the main progressing chart are designed.In this design, three-store freight elevators can be applied by PLC controlling and activated with variable frequency. Also, the computer communication succeeds to operate on the surveillance of the freight elevator and completes the running controlled indirectly on the computer. Therefore, it is supposed that it is feasible to use PLC to control freight elevators and focus on monitoring them between buildings...