[Asia Pump Network News] User water consumption is generally dynamic, so inadequate water supply or over-supply situations have occurred. The imbalance between water and water supply reflected in the pressure on the water supply, you can install the pump frequency counter, through the control of the inverter to control the water pressure, water and water can be maintained between the balance, thereby increasing the water supply the quality of. Pump frequency conversion cabinet frequency changer in constant pressure water supply application First, the frequency conversion velocity modulation characteristic and the analysis Constant pressure water supply system is very important to the user. In the production of domestic water supply, if tap water supply is under pressure for a short period of time or for a short period of time, the quality of life may be affected. In severe cases, the safety of living will be affected. In case of fire, if water pressure is insufficient or water supply is not available, Cause significant economic losses and casualties. Therefore, the use of water supply area constant pressure water supply system, can produce greater economic and social benefits. With the development of power technology, the frequency control technology is improving day by day, the intelligent water supply control system with frequency conversion speed control as the core replaces the water supply equipment such as high level water tank and pressure tank. The starting is steady and the starting current can be limited within the rated current, Thus avoiding the start-up impact on the grid; as the average pump speed is reduced, which can extend the life of pumps and valves and other things; can eliminate the water hammer effect when starting and stopping. Its stable and safe operation performance, simple and convenient operation mode, and complete and thoughtful functions will enable the water supply to realize water-saving, energy-saving and labor-saving, and finally achieve the high-efficiency operation purpose. Second, the constant pressure water supply frequency conversion applications usually in the same water supply system, set more than one common pump, when the water supply is large more than one pump fully open, one hour or two water supply hours. In the use of frequency control of constant pressure water supply, the use of two ways, one of all pumps equipped with a converter; the second is equipped with a pump for each inverter. After the method according to the pressure feedback signal, through the PID operation automatically adjust the inverter output frequency, change the motor speed, and ultimately reach the goal of constant pressure pipe network, a closed-loop, simple, but high cost. The former method has the advantages of low cost and poor performance than the latter ones, but the control procedure is complicated and is the future development direction. The company developed the BC2100 series constant pressure water supply control system to realize the function of an inverter controlling an arbitrary number of motors. The principle described below is a drive drag multi-motor system. Third, the principle of PID control According to the feedback principle: in order to maintain a constant or substantially unchanged physical quantity, it should lead the physical quantity and constant value, the formation of closed-loop system. We want to keep the water pressure constant, so we must introduce the water pressure feedback value and the given value to form a closed-loop system. However, the system being controlled is characterized by a nonlinear, large inertial system. Nowadays the control and PID methods are combined to use fuzzy control when the pressure fluctuates greatly to speed up the response. PID is adopted to maintain the static accuracy when the pressure is small. This is through the PLC plus smart meters can nowadays the algorithm, while the PLC programming is now between the pump frequency and frequency switching. Practice has proved that using this method is feasible, and the cost is not high. In order to maintain the same pressure on the water supply network, according to the feedback theorem, the pressure transmitter is installed on the management of the pipe network system as a feedback element. Since the water supply system has long pipelines and large pipe diameters, the pressure in the pipelines is relatively slow. System is a big lag system, not easy to use PID regulator to control directly, but using PLC to control the way to achieve the role of control system. Fourth, the principle of frequency control Variable speed control to achieve constant pressure water supply, compared with the use of regulating valve to achieve constant pressure water supply, energy saving effect is very significant (according to the specific circumstances calculated). The advantages are: 1, start the balance, the starting current can be limited to less than the rated current, thus avoiding the impact on the grid when starting; 2, due to reduced average pump speed, which can extend the service life of pumps and valves; 3 , You can eliminate the water hammer effect when starting and stopping. Generally speaking, when a motor is controlled by one inverter, only the motor capacity of the inverter matches the actual motor capacity. When one inverter controls two motors at the same time, in principle, the capacity of the inverter equipped motor should be equal to the sum of the capacities of the two motors. However, if the water consumption at peak load is much different than the full-speed water supply capacity of two pumps, the inverter capacity may be appropriately reduced, but sufficient capacity should be reserved. Although the pump running at low speed, the motor current smaller work. However, when the user's water consumption changes frequently, the motor will be in frequent ascent and descent, and the current of the ascending and descending may slightly exceed the rated current of the motor, causing the motor to overheat. Therefore, motor thermal protection is required. For such a temperature rise caused by frequent ascent and descent speed, the electronic thermal protection function in the inverter is hard to play a protective role, so the thermal relay should be used for thermal protection of the motor. In the main function of presets, the highest frequency should be the motor rated frequency of the inverter maximum operating frequency. Ascending and descending time When using PID regulator, the rise and fall time should be set as short as possible to avoid affecting the dynamic response process decided by PID regulator. For example, if the inverter has PID adjustment function, the set up and down time will be automatically invalidated as long as the PID function is valid during presetting. Further Reading: pump valve pipe fittings Exhibition Water Expo Xiamen exhibition of marine equipment Internet + Forum Yiwu Fair 2016 exhibition mold top ten brands of the Internet information industry (Xiamen) Technology Co., Ltd. Author: Asian pumps Network Editor: Yao Xiaoxia (QQ / WeChat: 2355962924) http://beng.liuti.cn/ (Service Hotline: 400-6030-811)