PLC-based application for the control of condensing pressure

WEI Ji-jun， YUAN Zhe， YANG Ming-ling， WANG Kun， CHENG Zhen， TANG Ji-bao
（Hefei General Machinery Research Institute， Hefei 230088， China）

Abstract： The condensing pressure is one of the main parameters of the refrigeration cycle，which has a direct influence on the effect，security reliability and energy consumption level of the refrigeration device. Aiming at such questions as the analysis of the main factors that influence the condensing pressure in refrigeration system not being detailed enough，the method to overcome the interference factor not being explicit，the controlling accuracy not being high，and the control process not being distinct，on the basis of the theory of feedforward-feedback controlling model，a set of control system was designed especially by using the programmable controller （PLC） as the controlling core and taking a touch screen （TP170A） as the monitor screen. Besides，a simulation analysis on the influential factors of condensing pressure was handled，a comparison between their advantages and disadvantages of the classical control model of and feedforward–feedback controlling model in the engineering application was made，and the realization process of controlling system was presented clearly. The results indicate that the designed controlling system can manage the application of every kinds of the controlling model with the great improvement of the condensing pressure control accuracy，the well suppression of the interference factors. Meanwhile，the parameters is managed to be monitored，the faults will be alarmed，and the man-machine dialogue are realized，the whole refrigeration system is to operate stably and reliably.
Key words： feedforward-feedback； PLC； condensing pressure