Under the premise of meeting the flow and pressure requirements of various irrigation states, the system uses a frequency converter to control two main pumps (1, 2 pumps) with a power of 15kW using a time-sharing control method. Another auxiliary pump (No. 3 pump) with a motor power of 3.7 kW is operated directly under power frequency conditions to supplement the water pipes and valves. The control part of the system control part adopts Matsushita Electric Industrial FP0 series PLC, which is a modular PLC suitable for small control occasions. Its control unit with 8-point input and 6-point output can be expanded up to 110 points; the instruction is rich, there are 83 Basic instructions and 114 advanced instructions can be used. Advanced instructions include pulse output function, position control, PWM output function, PID calculation, etc. FP0 series PLC executes programs faster, each basic instruction only needs 0.9s, which can meet The need for a lot of computing. The FP0 series PLC control unit can use the analog input and output unit as an expansion module. The series of analog input and output units has two analog input channels and one analog output channel. The input and output ranges can be selected by DIP switches. The input range is: thermocouple; 5) J-type thermocouple; 6) T-type thermocouple. The output range is -10+10V and 020mA. Input and output electrical technology and automation Xia Xiaobing, etc., based on the PID control mode of the variable frequency constant pressure water supply system resolution of 1 / 4000. Inverter In this system, the inverter is used to control two 15kW pumps 0016-3. The frequency converter can drive a 15kW motor in the square torque mode. The control terminal of the frequency converter has two programmable analog inputs and a programmable analog output. The man-machine interface uses the PWS500S HMI of Taiwan Delta Company to complete the data input and status display of the system. PWS500S type HMI uses touch screen technology, friendly interface, easy programming, and can communicate with many manufacturers' PLCs. The use of HMI simplifies the design of the operator panel, making it easy to modify and speeding up the design of the system. The switching line switching line is composed of an AC contactor and performs the following functions: 1) controlling the start and stop of the pump with a motor power of 3.7 kW at the power frequency state; 2) the pump with a power of 15 kW at the power frequency state Start and stop; 3) operation of two pumps with a motor power of 15 kW in the inverter state; 4) hardware interlock. Pressure sensor The maximum working pressure of this system is 0.5MPa. The remote pressure gauge with the range of 0-1.0MPa can be used to obtain the voltage signal corresponding to the pressure. Manually run manual operation for system debugging to test whether all parts of the system are normal. That is to say, the main pumps of No. 1 and No. 2 are respectively operated under the control of the inverter, and the main pumps of No. 1 and No. 2 are not operated at the same time. At the same time, the PID control works, and the water pressure does not exceed the set pressure in the manual state. The auxiliary pump No. 3 can be directly connected to the three-phase AC power supply and automatically shut off when the water pipe pressure reaches the set pressure. In the automatic running state, the control system first detects the pressure of the water pipe, and when the pressure is lower than the set value, the auxiliary pump is started to replenish water. Within the set time, when the water pipe pressure can reach the set value, the auxiliary pump operation is stopped. At this time, it is considered that the water pipe pressure drop is caused by the leakage of the pipeline system or a small amount of water, and the main pump does not operate. After the auxiliary pump is started, if the pipeline pressure cannot reach the set value within the set time, the auxiliary pump stops running and the main pump marked as A by the control system is started. After the main pump is marked as A, if the pipeline pressure reaches the set value and the inverter runs below the minimum water output frequency corresponding to the pressure set value, stop the pump operation and mark the other pump. Set to A. After the main pump is marked as A, the inverter runs at 50Hz for a period of time and the pipeline pressure does not reach the set value, then switch A to the power frequency operation, and the inverter starts to be the main pump of B. If the pipeline pressure reaches the set value, electrical technology and automation Xia Xiaobing, etc., based on the PID control mode of the variable frequency constant pressure water supply system machinery manufacturing and automation and the inverter runs below the minimum water output frequency corresponding to the pressure set value, Then stop the pump running at the power frequency, and the original variable frequency pump works according to the above procedure. The two main pumps are marked with A in turn, which avoids one frequent start and the other does not run for a long time when the water consumption is small. Panasonic Electrician FP0 series PLC provides PID calculation function, the instruction is F355, its parameter setting is flexible and easy to use. The calling method of the F355 instruction is: where R0 is the trigger signal for executing the PID instruction. S is the PID address parameter setting and the first address of the memory area required to execute the instruction. The allocation is as follows: control mode set value feedback value output value output upper limit setting output lower limit setting proportional gain constant Kp integral time constant Ti differential time constant Td control The cycle automatic tuning process flag PID processing process provides two types of working mode selections using the FP0 PID command, which are direction selection and integration mode selection. Direction selection is the function of selecting the direction of change of output when the feedback value changes. When the feedback value drops, the reverse mode of operation will cause the output to rise, suitable for heating or a similar process; when the feedback value rises, the forward mode of operation will cause the output to rise, suitable for cooling or a similar process. The integration mode selection can select different working modes of the PID instruction. When the set value (PI-D) changes, the output value changes slowly, and it takes a long time to reach the steady state; the proportional integral type (I-PD) changes rapidly when the set value is changed, and can be stabilized quickly. status. The selection of the working mode is set in the first address S. At the same time, the system can be automatically tuned by setting the flag in S to obtain the PID parameter. This function can speed up the system debugging. The parameters are automatically called in the pump system of variable frequency control operation. The water pump controlled by the frequency converter is limited by the lift head. Under different working pressures, the minimum water output frequency of the water pump is different. Running below the minimum water output frequency will bring disadvantage to the water pump. influences. Through calculation and experiment, the minimum water output frequency under different working pressures is obtained, and the table is stored in the PLC. When the operator changes the working pressure through the man-machine interface, the PLC automatically adjusts the settings to make the system work in good condition. After field experiments, the design requirements can be met under different working conditions. The system meets the design requirements and is put into operation. Quartz fiber Braided Sleeve is a type of protective sleeve made from high-purity quartz fibers. It is commonly used in high-temperature applications where excellent thermal and electrical insulation properties are required. Quartz Fiber Braided Mesh,Quartz Fiber Braided Sleeve,Quartz Fiber Sleeving,Quartz Fiber Cable Sleeve Dongguan Liansi Electronics Co.,Ltd , https://www.liansisleeve.com