| Electric hoist is an important part of hot dip galvanizing process, the better control of electric hoist is vital. At present, the existing electric hoists of our country are mostly controlled by relay, which has many disadvantages such as low degree of automation, poor security and reliability, high accident rate, more human cost and low industrial efficiency, and is not conducive to the stable operation of the electric hoist. Therefore, it is imperative to design an advanced automatic production line control system which can significantly enhance production efficiency and improve product quality.Based on the hot galvanizing production line of Jiuwang Metals Corporation (Hengshui city, Hubei province) as design object, this paper deeply analyzes the hot dip galvanizing process flow and designs a intersecting three-dimensional variable frequency speed control system for hot-dip galvanizing line based on PLC. Taking Siemens S7-300PLC as the core, the main system structure components including piano style console, frequency conversion box and electric hoists, as well as control circuits for single hoist and multiple hoists, PLC input and output hardware circuits are designed. The console includes multiple functions such as digital tube displaying, equipment alarming and resetting. The automation control system is constructed by using the PROFIBUS bus technology. Using STEP7software as design platform, the main system control program, subroutines for single hoist control and intersecting three-dimensional control between multiple hoists are written. The hot galvanizing production line is monitored by using Kingview software simulation.Under the premise of correct hardware and software designs, the whole system simulation are performed, including the tests of electric hoists, system console and frequency conversion box. Test results indicate that the hardware and software designs meet the control system requirements, and can be used in industrial field. |
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