The Application Of AC Frequency Control Technology For PE Load

With the higher requirement on speed control for bridge type grab ship unloader, the normal method of speed control e.g. by wound-rotor asynchronous motor connected with resistor in series or by thyristor stator and cascade, has common disadvantages like periodic maintenance on collecting rings and electrical brushed and more relies and contactors and all this obviously not meet the requirement of industrial production.With the development of electric and electrical technology, the alternating current (AC) frequency control technology increasingly showed the excellent performance in speed control, high efficiency and easy maintenance, as well lower price and became the optimized speed control program for lift machinery. If the AC frequency control technology was successfully used for lifting mechanism of bridge type grab ship unloder, the selection of frequency converter and its peripheral accessories must be around the ship unloader to assure of operation in safety and reliability by using special measures of assembly and wiring.This paper, combining theory with practice, studied on frequency control on potential load of lifting mechanism of bridge type grab ship unloader. First, this paper introduced the load characteristics of lifting mechanism of ship unloader, analyzed on the problems in the method of normal speed control and described characteristics of speed control with load in details. Second, this paper studied on AC speed control system, as well the basic control method and its characteristics, basic principle of vector control, calculation method of converter and calculation principle of peripheral accessories of converter and calculation formula. Finally, this paper described the application of frequency control system on potential load for bridge type grab ship unloader(1800t/h) in Zhejiang Zhoushan Laotang Port Project Phase-V.The program and calculation method of AC frequency control on potential load in this paper had been successfully used for the lifting mechanism of bridge type grab ship unloader (1800t/h) in Zhejiang Zhoushan Laotang Port Project Phase-V. It has been found that the lifting mechanism with frequency control had a simplified wiring and optimized performance compared with normal speed control by wound-rotor asynchronous motor connected with resistor in series, together with perfect fault diagnosis and display of converter and PLC, the speed control system substantial improved the reliability and maintainability.The application of AC frequency control in industry provided an entirely new plan of speed control in large range and high quality for lifting mechanism of bridge type grab ship unloader. The AC frequency control had been the mainstream of development for bridge type grab ship unloader owing to its high efficiency, energy saving, simplified wiring, less maintenance, perfect monitoring function and reliable operation.This paper, based on the principle of safety, reliability and availability, made design for the lifting mechanism of bridge type grab ship unloader with AC frequency control and realized the desired object with professional design and multiple functions.