1、 外文资料翻译 Water Tower Water Level Control System Research And Design Abstract: The water tower is a water level control system for residential quarters of Chinas extensive use of the water supply system, the existence of the traditional control methods to control the accuracy of the low power consumpt
2、ion of the shortcomings of large, research-based PLC controlled multi-pump cycle frequency constant pressure water supply system, using programmable logic controller, inverter, as well as devices such as pressure transmitter, complete logic control, speed control and data sampling frequency and othe
3、r functions, allowing the system to achieve automatic control, to achieve the purpose of energy conservation, improve the quality of the water supply system. Key words: PLC, inverter,constant pressure water supply 0 Introduction Water tower water level control system is the wider use of residential
4、quarters of Chinas water supply system, water supply systems in most of the traditional use of water towers, water tanks, or high pressure tank pressurization equipment to pump water higher than the actual height of the head to upgrade of water, the the result of increased water pump shaft power and
5、 energy consumption. Research and design of the towers is the water level control system uses a 1 constant pressure water supply system, stepless speed pumps. Automatically based on changes in water-conditioning system operating parameters to maintain a constant pressure to meet the water requiremen
6、ts of todays advanced, energy-saving and reasonable water supply system 1. Pump started, pid controller pressure transmitter to the control point to provide the pressure signal, when the pressure point is not equal to set value, pid controller by adjusting the inverter output frequency to change the
7、 pump speed to regulate the pipeline pressure constitutes a closed-loop feedback control system, water pressure regulator so that users timely, small fluctuations in results. And in the process control system designed to take full account of the principle of load balancing, to take first-in-first ou
8、t strategy of lining up, the way the implementation of the rotating frequency to ensure that the basic balance of the water usage. 1 Frequency Control Constant Pressure Water Supply Principle Frequency Control Constant Pressure Water Supply System by the programmable logic controller (plc), converte
9、r (built-pid), pressure transmitter, low-voltage electrical and pump components, such as Figure 1. Map m1 m3 for water pump motors, p1 p3 for pumps, km1 km6 for motor starting and stopping each of the AC contactor switch. Basic working principle of the system: by the plc a signal to the inverter to
10、control the water cycle work, when the large volume of water consumed by the plc control of all water line installed in the outlet pipe of the pressure transmitter, pressure standard signals into dc 0 v 10 v into the analog signal converter with pid regulator, pressure settings and pressure feedback
11、 values after the implementation of pid calculated values of the output of a frequency converter to set the value for the pump by the inverter to provide variable frequency electrical power to realize stepless speed regulation of electric pumps to regulate the exit of the water supply pipe network p
12、ressure, constant pressure water supply to achieve the purpose. Pressure feedback signal in order to ensure an accurate value, yet the value of feedback signal to set the filter time constant. The scope of the power converter, Figure 1 can increase the number of the motor to achieve a multi-trailers
13、, Optimization of the program. 2 towers of water level control system design Frequency according to the principle of constant pressure water supply system the design water level control system of the water tower block diagram shown in Figure 2, the city water network eq with the water level controll
14、er to control the injection valve yv1, as long as the water level below the high water mark, then to the pool water automatically. Pool of high / low water level signal directly to the plc, as a high / low level alarm. In order to ensure continuity of supply, the water level of the smaller distance
15、between the upper and lower limits. Domestic water and fire water pump three shared 3, usually yv2 solenoid valve in a state of loss, the closure of the fire pipe network, when a fire occurs, the solenoid valve was yv2 electricity, water distribution network with the closure of life, three water pum
16、ps for fire use, and maintain high-pressure fire water value. After the lifting of the fire, three use domestic water pump replaced and the cycle of operation, to maintain constant low water value. Each pump motor can run frequency, and frequency can be run. When the small volume of water consumed,
17、a water pump under the control of the converter stable operation of large quantities of water to the pump when running at full speed there is no guarantee that the pressure on network stability, plc pressure given the lower limit of the inverter signal and high-speed signal at the same time plc was
18、detected, plc automatically work in the original state of the pump frequency into frequency operation, in order to maintain the continuity of pressure at the same time use the next pump put into operation after start-up converter in order to increase the supply pipe network pressure of water to ensu
19、re stability； if running two pumps can not meet the requirements of the pressure, the frequency of work will be followed by a state into the pump-frequency operation, and then pump into a variable frequency operation； when the water consumption reduction, the first performance inverter has been work
20、ing effectively at the lowest speed signals, when the pressure signal, such as the ceiling is still there, plc will be the first first run of the pump frequency to quit in order to reduce the volume of water supplied, when the two signals when there are still, plc and then quit second frequency of t
21、he pump to run until a constant pressure water supply pump with frequency converter. All pump motors start from a stop to and from the start to stop by the inverter to control to achieve soft-start with set, to avoid the start of high-current impact to the pump motor to extend the life of the motor.
22、 At the same time, the use of variable frequency operation of the system pumps water cycle in order to first to open the first gate of the order of related pumps, so that both the water supply system to ensure back-up water pumps, water pumps and the system have the same running time as effective in
23、 preventing back-up pump death occurred not long-term phenomenon of rust and improve the comprehensive utilization rate of equipment, reducing maintenance costs. Electrical control system main circuit see Figure 3. AC contactor km1, km3, km5 were three pump motor control m1, m2, m3 frequency operati
24、on； AC contactor km2, km4, km6 respectively control m1, m2, m3 of Frequency operation； fr1, fr2, fr3 thermal relay for protection of the three pump motor overload； qs1, qs2, qs3, qs4 respectively, and three pump motor inverter main circuit isolation switch； fu1 fu3 mainly The fuse circuit. The syste
25、m works in manual mode, plc alarm detection only by the artificial adoption of panel buttons and switches From water pumps to stop and switch； the system works in automatic mode, all controlled by the plc completed report to the police. 3 towers of water level control system software design The main
26、 function of the automatic control system is achieved through software in light of the foregoing 1 control constant pressure water supply system requirements, water towers of the main process control system shown in Figure 4. Use of the timer interrupt function of the realization of pid control regu
27、lar sampling and output control, three pumps to generate switching signals, the signal contacts of the integrated logic control and alarm handling by the program. In program design to take full account of the principle of load balancing, to take first-in-first out strategy of lining up, the way the
28、implementation of the rotating frequency to ensure that the basic balance of the water usage. Constant pressure of life and fire of the two pairs of constant digital value is used directly in the proceedings set. Life when the water supply system for the full-scale settings of 70%, when the fire wat
29、er supply system for the full-scale settings of 90%. Pid loop gain and time constant is initially set at: gain kc = 0.25, sampling time ts = 0.2 s, integration time ti = 30 min. in accordance with specific conditions need to be further adjusted in order to achieve optimal control. To a constant wate
30、r supply, landing in the water pressure to increase the inverter output frequency, when the maximum frequency converter and a constant pressure pump can not meet the requirements, while running the pump frequency to switch to the running frequency, At the same time need to start a second frequency o
31、r third pump until the water supply to meet the requirements. Need to determine criteria for the launch of a new water pump is the inverter output frequency is set to reach the upper limit. In order to determine the frequency of the inverter limits the accuracy of least squares by chance should be t
32、he frequency of the frequency of fluctuations in the ceiling from the situation. Inverter control motor pumps are activated each time the soft-start, and requires the use of water pumps must turn to serve as a continuous variable frequency pump operation shall not exceed 3 h, each time when the need to launch a new water pump, the pump will run from the existing removal of the inverter, and replace the power-frequency operation, reset the inverter and run the pump for a
