Frequency conversion regulation of the energy of t

  • Detail

Screw this is a loosely structured manipulator designed by NASA engineers. It is a composite part of the variable frequency regulation of the energy of the rod chiller. The working principle of the variable frequency drive device. The VSD (variable speed device) screw chiller with variable frequency drive adopts a unique adaptive cooling control logic to synchronously adjust the motor speed, slide valve opening, slide block position and throttle valve opening according to the changes of working conditions, Make the slide valve position, compressor speed, content product ratio and evaporator liquid supply always maintain the best match, so as to ensure that the unit always operates under the best working conditions. 2. Logic control 2.1 temperature control the basic parameters of VSD control are the deviation between the actual outlet temperature of cold water and the set value, and the motor speed and slide valve position are adjusted according to the temperature difference. When the unit operates at full load, the slide valve is fully closed, and the motor speed logic module is completely controlled by temperature deviation. As the load decreases, adjust the input current frequency through the variable frequency drive device until the motor speed reaches the minimum. If the load continues to decrease, the spool valve gradually opens, and the spool valve control logic module determines the opening of the spool valve according to the actual working conditions; When the unit needs to be loaded, the current frequency is adjusted by the variable frequency drive device to improve the motor speed. At the same time, the pressure protection device always detects the evaporation pressure and condensation pressure of the unit to prevent the system from overload. 2.2 regulation of volume ratio in the process of temperature regulation, the internal and external pressure ratio of the chiller will constantly change. The control system adjusts the position of the slider according to the ratio of condensation pressure and evaporation pressure, so that the internal pressure ratio of the compressor is equal to or close to the external pressure ratio. At the same time, the pressure ratio of the unit limits the change of motor speed and the action of slide valve, and controls the flow of refrigerant into the evaporator. 3. Energy saving analysis of VSD using VSD can make the additional power consumption caused by the imbalance of internal and external pressure ratio of the unit; When the load of the unit is low (less than 60%), the effective length of the slide valve will not be shortened, which avoids the steep drop in efficiency under low load conditions when the slide valve is used for regulation. At the same time, the automatic regulation of the liquid supply makes the refrigerant flow into the evaporator maintain the optimal value. Therefore, the energy-saving effect of using the variable frequency drive device at low load is obvious. Table 1 shows the comparison of energy consumption measured by constant speed slide valve regulation and VSD regulation for the same type of screw chiller under the same working conditions. It can be seen from table 1 that the screw chiller with variable-frequency drive device saves more than 20% energy on average, and the lower the load, the more obvious the energy-saving effect is that its thermal insulation performance can be superior to that of all other types of thermal insulation materials, such as about 30% when the load is 20%. In addition, the variable frequency drive device can automatically correct the power factor, so when the unit is in normal operation, it can ensure that the power factor is not less than 0.95, so as to further improve the utilization of power equipment without damage. 4 conclusion through the above analysis and measurement, it can be found that: a) the screw chiller can achieve economic operation within a large load change range by using VSD regulation method, especially under low load, the energy-saving effect is more significant. b) Through the simulation calculation, it is found that when the outlet water temperature of the refrigerant is required to be lower, the energy-saving effect of the refrigeration unit driven by the frequency converter is more obvious. c) Through the optimization and matching of adjustment methods, the adjustment range of refrigerating unit load is increased and the number of downtime caused by low load is reduced; At the same time, integrating the overload protection function of the unit into the main control module can improve the safety and reliability of the system operation

Copyright © 2011 JIN SHI