PLC恒压供水英文简介

Converter in the application of constant pressure water supply

I. Frequency analysis of the characteristics and
The number of water users is constantly changing, so the water supply shortage or excess supply occur from time to time. Water supply and water and reflects the imbalance between the pressure in the water, that is more water and less water, the pressure is low; less water and more water, then pressure. To maintain a constant pressure water supply, water supply and water can maintain a balance between, that is, supply of water for a long time also, water is also less water is low, resulting in improved water quality.
Constant Pressure Water Supply System for certain industries or special user is very important. For example, in some of the production process, if for some reason the pressure of water supply is inadequate or short-term water, which may affect product quality and serious end-of-life products and equipment damage. Another example is case of fire, if the water pressure or inadequate or no water supply, fire can not be quickly, may lead to substantial economic losses and casualties. Therefore, the use of certain areas of constant pressure water supply system, with great economic and social significance.
With the power and technology, VVVF technology is getting more sophisticated in order to Frequency of water supply as the core of the intelligent control system replaces the previous high pressure tanks such as water tanks and water supply equipment, a smooth start-up, may limit the starting current at rated current within the start-up so as to avoid the impact on the power grid; as a result of the average pump speed is reduced, which may be extended for things such as pumps and valves of life; can be eliminated at the time of start-up and shutdown of water hammer effect. Stable and secure operation of its performance, simple operation, as well as the complete and thoughtful features, will allow water to achieve water-saving, energy-saving, labor-saving, and ultimately to achieve the purpose of efficient operation.
Second, the frequency constant pressure water supply applications
Usually in the same way the water supply system, set up more than one commonly used pumps, large water pumps at more than full, the amount of water an hour to open one or two. Frequency Control for the introduction of constant pressure water supply when used in two ways, first, all from a single pump with frequency converter; pumps with each other is to use a converter. Methods based on the pressure after the feedback signal, through the PID operation automatically adjusts output frequency converter to change the motor speed, and ultimately to achieve the purpose of constant pressure pipe network, on a closed-loop circuit, relatively simple, but its high cost. Methods before the low-cost, performance worse than the latter, but more complex control procedures, is the future direction of development, I developed NKL-A series of constant pressure water supply control system can achieve an arbitrary number of inverter motor control function. Following the principles mentioned are more than a drag motor inverter systems.
Third, PID control principle
According to the feedback principle: in order to maintain a physical change or will remain basically unchanged, it should be cited in this physical and constant comparison, the formation of the closed-loop system. If we want to maintain a constant water pressure, so water pressure should be introduced and given the value of feedback value to form the closed-loop system. However, the characteristics of the control system is nonlinear, large inertia of the system, PID control and is now a combination of methods, the pressure fluctuation in the use of large fuzzy control, to speed up the response time; in the pressure range used in smaller PID to maintain static accuracy . This intelligent instrument through the PLC can be added when the algorithm is, at the same time when the PLC is programmed to pump-frequency and frequency switch between. Practice has proved that the use of this method is feasible and cost is not high.
Water supply networks in order to maintain the pressure constant, based on feedback control theorem in the management system of the pressure transmitter is installed as a feedback component, due to the water supply system pipe length, diameter, and pipe network will slow the filling pressure Therefore, large time delay system is a system, not directly control the PID regulator, and the use of PLC to participate in a controlled manner to achieve the regulatory role of the control system.
Fourth, the principle of variable frequency control
Frequency Control with constant pressure to achieve the water supply, and with constant pressure regulating valve to achieve the water supply as compared to significant energy savings (which can be calculated in accordance with the specific situation). Its advantages are:
   1, starting balance and starting current less than rated current limit in order to avoid the starting grid at the time of impact;
   2, as a result of the average pump speed is reduced, in order to extend the pump and valve service life, etc.;
   3, can be eliminated at the time of start-up and shutdown of water hammer effect;
Generally speaking, when a frequency converter controlled by a motor, just to make use of the motor with the inverter capacity in line with the actual capacity of your motor. When a frequency converter to control two motors at the same time, the principle of allocation by inverter motor capacity should be equal to two electric motors and the capacity. However, if the peak load in the water than the volume of two water pumps at full speed when a lot of difference,

Could be considered appropriate to reduce the capacity of inverter, it should be noted that sufficient capacity.
Although the pump is running in low speed, the smaller motor operating current. However, when users change the water frequently, the motor will be in frequent or, deceleration state, and the rise of the current deceleration can be slightly more than the motor rated current, leading to motor overheating. Therefore, the motor thermal protection is necessary. Such or as a result of frequent, deceleration and the accumulated temperature rise, inverter electronic thermal protection function is difficult to play a protective effect, it should be used for motor thermal relay thermal protection.
Preset in the main function, the maximum frequency should be based on the rated motor frequency of the maximum operating frequency inverter. Or, deceleration time in the use of PID regulator, the rise, deceleration time should be set shorter as far as possible, so as not to affect the decision by the PID regulator of the dynamic response of the process. Such as the inverter itself is PID regulator function, as long as the PID in the pre-set function effectively, then set the deceleration time or speed and will automatically lapse.
Fifth, the characteristics of constant pressure water supply system
   1, power: energy-saving control software optimized to achieve maximum pump energy-saving operation;
   2, water-saving: the situation in accordance with the actual water pressure pipe network settings, automatic control of water pumps, reducing water run, missed the phenomenon;
   3, reliable operation: from frequency converter to achieve soft-start pump to pump frequency from the frequency of non-impact of switching to prevent the impact of pipe network, pipeline network to avoid the pressure gauge, pipe rupture.
   4, network function: the use of the entire Chinese industrial configuration software, real-time monitoring of various sites, such as the motor voltage, current, frequency, pipe network pressure and flow. And to build up the power consumption of each site, each pump out the accumulated water, while providing various forms of print statements in order to analyze the statistics.
   5, flexible control: sub-water supply, regular water supply, manually select the work.
   6, self-protection function: if a failure of pumps and take the initiative to issue a report to the police drive up digital information, at the same time start the standby pump to maintain water balance. The event of failure of automatic control system, the user can directly operate the system manually in order to protect the water supply.
Sixth, the scope of system
   1, water plant, pressure pumping station
   2, the residents living area, guest houses and other construction
   3, production of water
   4, boiler circulating water system
   5, farmland irrigation system

Frequency analysis of the characteristics

The number of water users is constantly changing, so the water supply shortage or excess supply occur from time to time. Water supply and water and reflects the imbalance between the pressure in the water, that is more water and less water, the pressure is low; less water and more water, then pressure. To maintain a constant pressure water supply, water supply and water can maintain a balance between, that is, supply of water for a long time also, water is also less water is low, resulting in improved water quality.
Constant Pressure Water Supply System for certain industries or special user is very important. For example, in some of the production process, if for some reason the pressure of water supply is inadequate or short-term water, which may affect product quality and serious end-of-life products and equipment damage. Another example is case of fire, if the water pressure or inadequate or no water supply, fire can not be quickly, may lead to substantial economic losses and casualties. Therefore, the use of certain areas of constant pressure water supply system, with great economic and social significance.
With the power and technology, VVVF technology is getting more sophisticated in order to Frequency of water supply as the core of the intelligent control system replaces the previous high pressure tanks such as water tanks and water supply equipment, a smooth start-up, may limit the starting current at rated current within the start-up so as to avoid the impact on the power grid; as a result of the average pump speed is reduced, which may be extended for things such as pumps and valves of life; can be eliminated at the time of start-up and shutdown of water hammer effect. Stable and secure operation of its performance, simple operation, as well as the complete and thoughtful features, will allow water to achieve water-saving, energy-saving, labor-saving, and ultimately to achieve the purpose of efficient operation.

Constant pressure water supply of the inverter application

Usually in the same way the water supply system, set up more than one commonly used pumps, large water pumps at more than full, the amount of water an hour to open one or two. Frequency Control for the introduction of constant pressure water supply when used in two ways, first, all from a single pump with frequency converter; pumps with each other is to use a converter. Methods based on the pressure after the feedback signal, through the PID operation automatically adjusts output frequency converter to change the motor speed, and ultimately to achieve the purpose of constant pressure pipe network, on a closed-loop circuit, relatively simple, but its high cost. Methods before the low-cost, performance worse than the latter, but more complex control procedures, is the future direction of development, I developed NKL-A series of constant pressure water supply control system can achieve an arbitrary number of inverter motor control function. Following the principles mentioned are more than a drag motor inverter systems.

PID control principle

According to the feedback principle: in order to maintain a physical change or will remain basically unchanged, it should be cited in this physical and constant comparison, the formation of the closed-loop system. If we want to maintain a constant water pressure, so water pressure should be introduced and given the value of feedback value to form the closed-loop system. However, the characteristics of the control system is nonlinear, large inertia of the system, PID control and is now a combination of methods, the pressure fluctuation in the use of large fuzzy control, to speed up the response time; in the pressure range used in smaller PID to maintain static accuracy . This intelligent instrument through the PLC can be added when the algorithm is, at the same time when the PLC is programmed to pump-frequency and frequency switch between. Practice has proved that the use of this method is feasible and cost is not high.
Water supply networks in order to maintain the pressure constant, based on feedback control theorem in the management system of the pressure transmitter is installed as a feedback component, due to the water supply system pipe length, diameter, and pipe network will slow the filling pressure Therefore, large time delay system is a system, not directly control the PID regulator, and the use of PLC to participate in a controlled manner to achieve the regulatory role of the control system.
Frequency Control Principle

Frequency Control with constant pressure to achieve the water supply, and with constant pressure regulating valve to achieve the water supply as compared to significant energy savings (which can be calculated in accordance with the specific situation). Its advantages are:
   1, starting balance and starting current less than rated current limit in order to avoid the starting grid at the time of impact;
   2, as a result of the average pump speed is reduced, in order to extend the pump and valve service life, etc.;
   3, can be eliminated at the time of start-up and shutdown of water hammer effect;
Generally speaking, when a frequency converter controlled by a motor, just to make use of the motor with the inverter capacity in line with the actual capacity of your motor. When a frequency converter to control two motors at the same time, the principle of allocation by inverter motor capacity should be equal to two electric motors and the capacity. However, if the peak load in the water than the volume of two water pumps at full speed when a lot of difference,

Could be considered appropriate to reduce the capacity of inverter, it should be noted that sufficient capacity.
Although the pump is running in low speed, the smaller motor operating current. However, when users change the water frequently, the motor will be in frequent or, deceleration state, and the rise of the current deceleration can be slightly more than the motor rated current, leading to motor overheating. Therefore, the motor thermal protection is necessary. Such or as a result of frequent, deceleration and the accumulated temperature rise, inverter electronic thermal protection function is difficult to play a protective effect, it should be used for motor thermal relay thermal protection.
Preset in the main function, the maximum frequency should be based on the rated motor frequency of the maximum operating frequency inverter. Or, deceleration time in the use of PID regulator, the rise, deceleration time should be set shorter as far as possible, so as not to affect the decision by the PID regulator of the dynamic response of the process. Such as the inverter itself is PID regulator function, as long as the PID in the pre-set function effectively, then set the deceleration time or speed and will automatically lapse.

Characteristics of Water Supply System

   1, power: energy-saving control software optimized to achieve maximum pump energy-saving operation;
   2, water-saving: the situation in accordance with the actual water pressure pipe network settings, automatic control of water pumps, reducing water run, missed the phenomenon;
   3, reliable operation: from frequency converter to achieve soft-start pump to pump frequency from the frequency of non-impact of switching to prevent the impact of pipe network, pipeline network to avoid the pressure gauge, pipe rupture.
   4, network function: the use of the entire Chinese industrial configuration software, real-time monitoring of various sites, such as the motor voltage, current, frequency, pipe network pressure and flow. And to build up the power consumption of each site, each pump out the accumulated water, while providing various forms of print statements in order to analyze the statistics.
   5, flexible control: sub-water supply, regular water supply, manually select the work.
   6, self-protection function: if a failure of pumps and take the initiative to issue a report to the police drive up digital information, at the same time start the standby pump to maintain water balance. The event of failure of automatic control system, the user can directly operate the system manually in order to protect water supply

System applications

   1, water plant, pressure pumping station
   2, the residents living area, guest houses and other construction
   3, production of water
   4, boiler circulating water system
   5, farmland irrigation system


Residential, commercial, residential quarters and (lower) the original of the supply of such general use of roof water tank means, ceiling water pump will hit the roof of the reservoir water storage tanks, roof water tanks in the use of their own re-pressed to water pipes. Water model is very simple, it is the most important issue of control of water above the working hours, and just the beginning, who specialized scheduling of duty by switching pumps, no open water pumps, water filled out on the pump clearance. This is not only troublesome, but also a waste of manpower, time to consider the relay to control the start and stop pumps to start better, but the seasonal changes and time changes, the relay set-up time will be re-adjusted, very troublesome. With the development of electronic technology to the present, a variety of pump start and stop the emergence of the controller, making the roof water tanks formed mainly as follows:
1, controlled electrical contact pressure gauge, the outlet pipe at the pump to install electric contact pressure gauge, roof water tanks Intake Department to install a floating ball valve, water filled up, the float valve shut down gradually, so that the water pressure pump gradually increased, reached a certain set value, the pressure gauge output signal will stop the pump.
2, Level-controlled, in the rooftop water tanks down the loading of a liquid level sensor, (such as the reed switch, float, etc.), the water level to a high level, water pumps stop, the water level dropped to under water level, water pumps stop.
3, the use of single-chip programmability make good pump operation control circuit board, combined with the above advantages in two ways, but also developed a good system.
The early 90s, emerging as a transducer electronic products enter the Chinese mainland manufacturers and engineering applications have taken place on its keen interest in it without the head of the motor speed control and motor does not change the mechanical properties inherent in in the water above the application has been the most perfect embodiment. In addition, the balance of the soft-start features, it has opened up a new field of frequency conversion constant pressure water supply. By the late 90's, many parts of the provisions of the new housing can not be above water tanks, water tanks cancel the original way. Thus, the frequency constant pressure water supply system has been fully mature and has been used in various construction developers.
This means the water supply up-to-date with the inverter technology is gradually improving, after a process.
Has only just started simple inverter speed control function, but constant pressure on the closed-loop must be done, it needs PID regulator. Also need to PLC (programmable logic controller) on the number of pumps used to control, in this case, the first, PLC programming needs of professionals, and the second, PID regulator parameters are not well adjusted, PID results are always unsatisfactory, so the beginning of a journey that many designers think that the system is enigmatic, it is difficult to grasp, do not simply give up, which is caused by the way the water is not pre-rapid development of the main reasons for good.
Inverters then begin to resolve these problems, the PID regulator built into the inverter, and a good adjustment, many of the parameters of the PI did not have to do to adjust the value of direct use of the factory can be a very good stability of the effect, and then put PLC functionality built into a variety of ways through the inverter, and some pieces of card manufacturers to make alternative model, some manufacturers supply directly to launch a special converter models, the design staff as long as a few simple settings parameter control can be achieved, by now referred to constant pressure water supply systems are beginning to express their views is very simple and very good use.
However, people began to put forward, and now the system is very simple, as long as the operation panel on the inverter to set several parameters can not solve the problem, but there are still some users are even not sure what is the frequency converter, but also the training for this user. Teach them how to operate. Problems can occur when operating parameters of failure to the trouble of setting the wrong people after a headache, so there have been using touch screen (HMI) + PLC formed a more advanced system, the use of staff as the Chinese use of small computer which can facilitate the visual input and want to read out the data, this point, the frequency constant pressure water supply system to the peak of development.
 
Frequency constant pressure water supply system

Frequency constant pressure water supply system is mainly composed of the following areas:
1, the inverter water
2, external and water pumps with electric control电控柜
3, pressure transmitter
4, PLC (Programmable Logic Controller)
5, HMI (touch screen, man-machine interface)