전류정보를 이용한 가변속냉동시스템의 열교환기 실시간 고장진단

Abstract

Recently, owing to system integration and automation, refrigeration system has become more complicated one. The refrigeration system is basically consisted of an evaporator, a condenser, a compressor, an expansion valve, and pipes connected to each part. For saving energy and improving efficiency, the use of a variable speed refrigeration system(VSRS)with a compressor driven an inverter and a motor is gradually increasing in the fields of heating, ventilating, and air-conditioning(HVAC) industry. However this tendency also causesdifficulty in finding fault causes when the system is failed. Especially, if faults are not detected immediately and are not treated adequately, even though simple faults of the system, they can cause economically huge damage by inducing whole system shut-down. In addition, energy consumption will be increased. Therefore, an efficient on-line fault detection and diagnosis(FDD) is very important to predict the performance degradation early and to prevent faults in advance1). The conventional studies for FDD have mainly depended on pressure and temperature information. The pressure and temperature information are basically monitored to confirm safety of the refrigeration system. Moreover, the pressure and temperature reflect static characteristics of a refrigeration system. However they are no longer enough for FDD of a VSRS. Because feedback control which is imperative to a VSRS causes compensation effect on the pressure and temperature. Inverters are essential to the VSRS in order to control compressor speed. Current from an inverter is useful for FDD of mechanical faults as well as electrical faults. The current information responds sensitively according to thermal load variation of a VSRSin case of mechanical faults. In addition, the current is hardly influenced by the compensation effect of feedback control. Thus, FDD for a VSRS based on the current information is faster and more precise than the one based on the pressure and temperature information. Also the current information can be utilized without extra cost because it is always measured on purpose to prevent overcurrent in an inverter. In this paper, two no fault model(NFM) is presented. One used current, pressure and temperature as variables of NFM(1). The other used only current as variable of NFM(2). And each FDD system according to two NFM is indicated such as experimental equipment and algorithm of FDD. Next, the experimental results by two FDD systems is shown. We could know that one by NFM(2) is better than the other by NFM(2) because it was faster and more precise FDD system in case of FDD system by NFM(2). And one by NFM(2) had easily reliability than the other. And the used reason of currnet in FDD system in VSRS is indicated and the principle of current as variable of FDD system in VSRS is presented.