1 .Introduction
With industrial control levels. Inverter constant pressure water supply device technology has been relatively mature. In the market to be good reflect. from the economical operation of the system is stable and reliable has been recognized by society. Along with the system controller and inverter technology development is continuously updated and developed. Controllers on the run. From the relay logic, microprocessor, PLC, dedicated controller steps. From Frequency Control, its development has undergone a number of speed control, Simulation given exclusive control of the controller. Every step of development mean that newer and better devices replace traditional methods. The system uses more advanced programmable logic control PLC as a controller to complete the frequency constant pressure water system based on the use of water in different Remote control through online pressure transmitter signal input to the PLC, PID automatic adjustment, pump control operations, to maintain pressure on the water supply pipe network. The system uses a more extensive and can be used for living, Fire and water supply industries in many respects. Below constant pressure to district water supply system as an example. Converter Technology in industrial control system applications. 2. Introduction Process
Most of the water supply system prior to using the traditional towers, water tanks, or high-pressure-boosting equipment, But they must pump water higher than the actual height of the pressure referred
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to \power and energy loss disc, and the user is not a constant pressure. pressure over the need for regular inflation. equipment increased the danger. Frequency is used without constant pressure water tower technology, can make up for these shortcomings. Frequency - control system through measurement of the pressure on the pipe network, by the PLC was built PID regulator after the operation. the converter output frequency to achieve the constant pressure of the water supply network, and from the water company for supply to the purification of water inflow of water east district, followed by a transducer control of the two motors and two-frequency pump the water to the district each user's home. According to users within the water pipe network to control the pressure of four pumps work mode. When the user less water consumption, only one pump operating frequency Taiwan to guarantee the constant pressure, when the larger water users, the system automatically activated the rest of the pump and put into operation. Community to ensure that users into the water pressure constant. 38
A motor and the motor from a B inverters to control, Frequency Motor collectively. in the smaller water consumption, According to two inverter pump controller mutual switching time. to extend motor life.
To prevent water users in a very, storage tanks water level is too high and aids out pools, Therefore, the increase in a Level interlock alarm control, to improve system security. 50,000 increase in the bottom of a venting valve, to be able to regularly clean water tanks to ensure that users of water cleanliness. 3 System control theory and composition
This system uses single-loop feedback control loop, The continuous acquisition system pressure pipe network signal and given SP (pressure settings), After Operators will deviation gave PID controller PID controller then signals gave implementing agencies, namely the electrical group, implementing agencies receiving the regulator orders to change their ways of operating, so that the pressure of change. So the cycle implementation. until the pressurepipe network in a constant state of the pressure. from this system from the environment (such as temperature) interference factors more pressure control belongs to lag control, Therefore, using PID control operation, to reduce the environmental interference. improve system stability and speed.
System testing tube pressure, and then judge of the pressure and the low-pressure limit set the difference between, if less than lower limit set pressure. Inverter system will be activated pump. Frequency pump power and the size depends on the size of the pressure signal.
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If the maximum frequency pump Gong the rate had not been run under control so that the pressure to achieve lower limit set value, then a system will be activated # motor, If this time limit has been set to achieve a low value, the system will return to the state at the beginning, Detection of continued pressure. Similarly, when the pump and an inverter frequency # pump running, Tube pressure limit has not yet been reached, low pressure setting, the system will activate the motor # 2. If this time limit has been set to achieve a low value, The system will be returned to the state at the beginning, Detection of continued pressure. If the pipe pressure has been limited to low-pressure setting. System will judge the pressure of a huge in the high-limit values. If there is no limit set to achieve the high pressure values, the system will return to the state at the beginning, Detection of continued pressure, has been set to achieve the high pressure limit value. The system will be parked motor # 2, If the limit is greater than the high-pressure setting value, the system will stop a # motor, If the limit is greater than the high-pressure setting value. Inverter system will regulate the pump power until ceases. With a transducer frequency to control two motors, when only one operating frequency pump at work state, and running for some time, the system will automatically switch to another frequency pump Taiwan,
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In exceptional circumstances or failure of the state, they can manually start each motor. And four motors are equipped with overload protection, short circuit protection, over-voltage protection and phase protection, overheating protection, over-current protection and overvoltage transient power outages automatic restart function restored.
3.2 System components
The system has a programmable logic controller, a converter, a converter, various conventional remote instrument, Motor Group, warning devices and other pipeline equipment, and the completion of major PLC the overall control system, receive the signals, the corresponding calculation the completion of various chain. Flowmeter selection is the instantaneous flow rate and total flow functions of the flowmeter, it is possible to calculate the total amount of water district.
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