Research On Electromagnetic Heating System For Agricultural Film Unit

China is a large agricultural nation, whether the use amount or the produc-tion amount of agricultural plastic film ranks among prostate in the world. With the wide use of agricultural plastic film, the plastic processing technology com-monly used has attracted more and more attention, but the traditional cast alu-minium heating method exists many faults such as large heat loss, low heat effi-ciency, high working environment temperature of injection molding machine, short service life, great maintenance amount and high waster rate, causing ex-tremely serious energy waste in the entire plastic processing industry.Aiming at the agricultural film unit exiting in the present market, we intro-duce electromagnetic induction heating technology to processing technology and develop a digital frequency- tracking electromagnetic induction heating system changing the traditional way of cast aluminum heating method. Electromagnetic induction heating technology is internal heating mode and has low surface tem-perature, high heat efficiency and small heat dissipation, shortening the unit pre-heating time and greatly saving electric energy. As agricultural plastic film unit heating process has strong nonlinearity, large time-delay and time-varying char-acteristics,we design an predictive identification-free adaptive temperature con-troller based on combining predictive control algorithm with identification-free adaptive control algorithm, accomplishing accurate temperature control, avoiding temperature overshoot, reducing debugging cycle and improving production quality. We adopt water-cooling method controlled by two bit two pass electro-magnetic valves with small water flow and direct water-cooling way, improving cooling efficiency and also reducing environmental noise. When heat tempera-ture exceeds the highest temperature pre-set, temperature control instrument con-trol relay close to open water control electromagnetic valve for cooling treatment. Experiments show that production energy saving rate can reach 54% and electricity saving quantity about 150kwh/t after using the agricultural film unit electromagnetic heating system designed in this paper. Electromagnetic heating system has remarkable characteristics such as quick heating, even, high heat utilization ratio, no pollution, good labor conditions and high reliability, effec-tively improving enterprise production efficiency and automation level. The sys-tem can remarkably save energy, effectively reduce the production and enhance the competitiveness of enterprises, providing a solution of energy saving devel-opment for plastic processing industry.