Nowadays, entering the 21st century, energy conservation and environmental protection have gradually become the mainstream consciousness of the society. In industrial applications, the implementation of water conservation projects has become a familiar trend of civilization development. However, do we really understand it? Accelerate the construction of water pollution control projects and promote the treatment of sulfur dioxide in coal-fired power plants. Raise funds for energy conservation and emission reduction through multiple channels. At this time, the inverter has come in handy.
First, the characteristics and analysis of frequency conversion speed regulation
User water usage is generally dynamic, so insufficient water supply or excess water supply can occur. The imbalance between water and water supply is concentrated in the pressure of water supply, that is, water is used more and water supply is less, the pressure is low; if water is used less and water supply is more, the pressure is high. Keeping the water supply pressure constant will balance the water supply and water consumption, that is, the water supply will be more when the water is used for a long time, and the water supply will be less when the water consumption is small, thereby improving the quality of the water supply.
Constant pressure water supply systems are very important to users. In the production of domestic water supply, if the tap water supply is insufficient or short-term water supply, it may affect the quality of life. In severe cases, it will affect the survival safety. In the event of a fire, if the water supply pressure is insufficient or the water supply is not available, it may not be extinguished quickly. Caused major economic losses and casualties. Therefore, the use of constant pressure water supply system in the water area can produce greater economic and social benefits.
With the development of power technology, the frequency conversion speed control technology is improving day by day. The intelligent water supply control system with the frequency conversion speed regulation as the core replaces the water supply equipment such as the high water tank and the pressure tank. The starting speed is stable and the starting current can be limited to the rated current. Thereby, the impact on the grid during starting is avoided; since the average speed of the pump is reduced, the service life of the pump and the valve can be prolonged; the water hammer effect at the time of starting and stopping can be eliminated. Its stable and safe running performance, simple and convenient operation mode, and complete and thoughtful functions will enable water supply to save water, save electricity, save manpower, and finally achieve high-efficiency operation.
Second, constant voltage water supply frequency conversion application
Usually, in the same water supply system, multiple common pumps are installed. When the water supply is large, multiple pumps are fully opened, and one or two water supply units are opened every hour. When using variable frequency speed regulation for constant pressure water supply, two methods are used. One is that all pumps are equipped with one inverter; the other is that each pump is equipped with one inverter. The latter method is based on the pressure feedback signal, automatically adjusts the inverter output frequency through PID calculation, changes the motor speed, and finally achieves the purpose of constant pressure of the pipe network, which is a simple closed loop, but the cost is high. The former method has low cost and the performance is not worse than the latter kind, but the control program is more complicated and is the future development direction. Our company developed the BC2100 series constant pressure water supply control system to realize the function of one inverter to control any number of motors. The principle described below is a system in which a frequency converter drives a multi-motor.
Third, the principle of PID control
According to the feedback principle: in order to maintain a physical quantity unchanged or substantially unchanged, this physical quantity should be compared with a constant value to form a closed-loop system. We want to keep the water pressure constant, so we must introduce the water pressure feedback value to compare with the given value to form a closed loop system. However, the system being controlled is characterized by a nonlinear, large inertia system. Now, the combination of control and PID uses fuzzy control when the pressure fluctuation is large to speed up the response; PID is used to maintain the static accuracy when the pressure range is small. This can be achieved by PLC plus smart meter, and the PLC is programmed to switch between the power frequency and frequency conversion of the pump. Practice has proved that using this method is feasible and the cost is not high.
In order to maintain the pressure of the water supply network, a pressure transmitter is installed as a feedback component in the management of the pipe network system according to the feedback theorem. Since the water supply system has a long pipe length and a large pipe diameter, the pipe network is relatively slow in charging. The system is a large lag system, it is not easy to directly use the PID regulator for control, and the PLC participates in the control to achieve the control system regulation.
Fourth, the principle of frequency conversion control
The use of variable frequency speed regulation to achieve constant pressure water supply, compared with the use of regulating valves to achieve constant pressure water supply, energy saving effect is very significant (can be calculated according to specific circumstances). The advantages are:
1. Starting balance, the starting current can be limited to the rated current, thus avoiding the impact on the grid during starting;
2, because the average speed of the pump is reduced, which can extend the service life of pumps and valves;
3. It can eliminate the water hammer effect during starting and stopping;
Generally speaking, when one motor is controlled by one inverter, it is only necessary to match the capacity of the inverter with the actual motor capacity. When one inverter controls two motors at the same time, in principle, the capacity of the inverter 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 of the two pumps, consider reducing the capacity of the inverter appropriately, but be careful to leave enough capacity.
Although the pump operates at low speeds, the operating current of the motor is small. However, when the user's water consumption changes frequently, the motor will be in a frequent rising and falling state, and the current of the rising and falling speed may slightly exceed the rated current of the motor, causing the motor to overheat. Therefore, thermal protection of the motor is required. For such temperature rise due to frequent rise and fall, the electronic thermal protection function in the inverter is difficult to protect, so thermal relays should be used for thermal protection of the motor.
In terms of main function presets, the highest frequency should be the highest operating frequency of the inverter with the rated frequency of the motor. When using the PID regulator, the rise and fall times should be set as short as possible to avoid affecting the dynamic response process determined by the PID regulator. If the inverter itself has the PID adjustment function, the set speed and deceleration time will be automatically invalidated as long as the PID function is set at the preset time.
Five, constant pressure water supply system features
1. Power saving: Optimized energy-saving control software to make the pump achieve maximum energy-saving operation;
2. Water saving: set the pressure of the pipe network according to the actual water consumption, automatically control the water output of the water pump, and reduce the running and leakage of water;
3. Reliable operation: The soft start of the pump is realized by the frequency converter, so that the pump can realize the non-impact switching from the power frequency to the frequency conversion, prevent the pipe network from impacting, avoid the pipe network pressure exceeding the limit, and the pipe is broken.
4, networking function: the use of all Chinese industrial control configuration software, real-time monitoring of various sites, such as motor voltage, current, operating frequency, pipe network pressure and flow. And it is able to accumulate the electricity consumption of each site, accumulate the water output of each pump, and provide various forms of printed reports for analysis and statistics.
5, flexible control: segmented water supply, regular water supply, manual selection of work methods.
6. Self-protection function is perfect: If a pump fails, it will send an alarm message to the upper machine and start the backup pump to maintain the water supply balance. In case of failure of the automatic control system, the user can directly operate the manual system to protect the water supply.
Sixth, the scope of application of the system
1, water plant, pressurized pump room
2. Residential areas, hotels and other buildings
3. Production water for enterprises
4, boiler circulating water system
5. Farmland irrigation system
The energy saving of the inverter is mainly reflected in the application of fans and pumps. In order to ensure the reliability of production, all kinds of production machinery have a certain margin when designing with power drive. When the motor can't run under full load, in addition to meeting the power drive requirements, the excess torque increases the consumption of active power, resulting in wasted power.
First, the characteristics and analysis of frequency conversion speed regulation
User water usage is generally dynamic, so insufficient water supply or excess water supply can occur. The imbalance between water and water supply is concentrated in the pressure of water supply, that is, water is used more and water supply is less, the pressure is low; if water is used less and water supply is more, the pressure is high. Keeping the water supply pressure constant will balance the water supply and water consumption, that is, the water supply will be more when the water is used for a long time, and the water supply will be less when the water consumption is small, thereby improving the quality of the water supply.
Constant pressure water supply systems are very important to users. In the production of domestic water supply, if the tap water supply is insufficient or short-term water supply, it may affect the quality of life. In severe cases, it will affect the survival safety. In the event of a fire, if the water supply pressure is insufficient or the water supply is not available, it may not be extinguished quickly. Caused major economic losses and casualties. Therefore, the use of constant pressure water supply system in the water area can produce greater economic and social benefits.
With the development of power technology, the frequency conversion speed control technology is improving day by day. The intelligent water supply control system with the frequency conversion speed regulation as the core replaces the water supply equipment such as the high water tank and the pressure tank. The starting speed is stable and the starting current can be limited to the rated current. Thereby, the impact on the grid during starting is avoided; since the average speed of the pump is reduced, the service life of the pump and the valve can be prolonged; the water hammer effect at the time of starting and stopping can be eliminated. Its stable and safe running performance, simple and convenient operation mode, and complete and thoughtful functions will enable water supply to save water, save electricity, save manpower, and finally achieve high-efficiency operation.
Second, constant voltage water supply frequency conversion application
Usually, in the same water supply system, multiple common pumps are installed. When the water supply is large, multiple pumps are fully opened, and one or two water supply units are opened every hour. When using variable frequency speed regulation for constant pressure water supply, two methods are used. One is that all pumps are equipped with one inverter; the other is that each pump is equipped with one inverter. The latter method is based on the pressure feedback signal, automatically adjusts the inverter output frequency through PID calculation, changes the motor speed, and finally achieves the purpose of constant pressure of the pipe network, which is a simple closed loop, but the cost is high. The former method has low cost and the performance is not worse than the latter kind, but the control program is more complicated and is the future development direction. Our company developed the BC2100 series constant pressure water supply control system to realize the function of one inverter to control any number of motors. The principle described below is a system in which a frequency converter drives a multi-motor.
Third, the principle of PID control
According to the feedback principle: in order to maintain a physical quantity unchanged or substantially unchanged, this physical quantity should be compared with a constant value to form a closed-loop system. We want to keep the water pressure constant, so we must introduce the water pressure feedback value to compare with the given value to form a closed loop system. However, the system being controlled is characterized by a nonlinear, large inertia system. Now, the combination of control and PID uses fuzzy control when the pressure fluctuation is large to speed up the response; PID is used to maintain the static accuracy when the pressure range is small. This can be achieved by PLC plus smart meter, and the PLC is programmed to switch between the power frequency and frequency conversion of the pump. Practice has proved that using this method is feasible and the cost is not high.
In order to maintain the pressure of the water supply network, a pressure transmitter is installed as a feedback component in the management of the pipe network system according to the feedback theorem. Since the water supply system has a long pipe length and a large pipe diameter, the pipe network is relatively slow in charging. The system is a large lag system, it is not easy to directly use the PID regulator for control, and the PLC participates in the control to achieve the control system regulation.
Fourth, the principle of frequency conversion control
The use of variable frequency speed regulation to achieve constant pressure water supply, compared with the use of regulating valves to achieve constant pressure water supply, energy saving effect is very significant (can be calculated according to specific circumstances). The advantages are:
1. Starting balance, the starting current can be limited to the rated current, thus avoiding the impact on the grid during starting;
2, because the average speed of the pump is reduced, which can extend the service life of pumps and valves;
3. It can eliminate the water hammer effect during starting and stopping;
Generally speaking, when one motor is controlled by one inverter, it is only necessary to match the capacity of the inverter with the actual motor capacity. When one inverter controls two motors at the same time, in principle, the capacity of the inverter 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 of the two pumps, consider reducing the capacity of the inverter appropriately, but be careful to leave enough capacity.
Although the pump operates at low speeds, the operating current of the motor is small. However, when the user's water consumption changes frequently, the motor will be in a frequent rising and falling state, and the current of the rising and falling speed may slightly exceed the rated current of the motor, causing the motor to overheat. Therefore, thermal protection of the motor is required. For such temperature rise due to frequent rise and fall, the electronic thermal protection function in the inverter is difficult to protect, so thermal relays should be used for thermal protection of the motor.
In terms of main function presets, the highest frequency should be the highest operating frequency of the inverter with the rated frequency of the motor. When using the PID regulator, the rise and fall times should be set as short as possible to avoid affecting the dynamic response process determined by the PID regulator. If the inverter itself has the PID adjustment function, the set speed and deceleration time will be automatically invalidated as long as the PID function is set at the preset time.
Five, constant pressure water supply system features
1. Power saving: Optimized energy-saving control software to make the pump achieve maximum energy-saving operation;
2. Water saving: set the pressure of the pipe network according to the actual water consumption, automatically control the water output of the water pump, and reduce the running and leakage of water;
3. Reliable operation: The soft start of the pump is realized by the frequency converter, so that the pump can realize the non-impact switching from the power frequency to the frequency conversion, prevent the pipe network from impacting, avoid the pipe network pressure exceeding the limit, and the pipe is broken.
4, networking function: the use of all Chinese industrial control configuration software, real-time monitoring of various sites, such as motor voltage, current, operating frequency, pipe network pressure and flow. And it is able to accumulate the electricity consumption of each site, accumulate the water output of each pump, and provide various forms of printed reports for analysis and statistics.
5, flexible control: segmented water supply, regular water supply, manual selection of work methods.
6. Self-protection function is perfect: If a pump fails, it will send an alarm message to the upper machine and start the backup pump to maintain the water supply balance. In case of failure of the automatic control system, the user can directly operate the manual system to protect the water supply.
Sixth, the scope of application of the system
1, water plant, pressurized pump room
2. Residential areas, hotels and other buildings
3. Production water for enterprises
4, boiler circulating water system
5. Farmland irrigation system
The energy saving of the inverter is mainly reflected in the application of fans and pumps. In order to ensure the reliability of production, all kinds of production machinery have a certain margin when designing with power drive. When the motor can't run under full load, in addition to meeting the power drive requirements, the excess torque increases the consumption of active power, resulting in wasted power.
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