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Application of HD31 in Constant Pressure Water Supply System
The traditional water supply scheme not only has high initial investment cost, but also high maintenance cost and labor investment in the later stage. In addition, the pressure of water supply is unstable, the power consumption is large, and the waste of water resources is also quite serious.
With the continuous development of society, human beings consume huge amounts of natural resources, and energy conservation and water conservation have become urgent social needs. Therefore, a new water supply scheme is imperative. In recent years, the constant pressure water supply scheme realized by frequency converters is very good. It solves the problems caused by the traditional water supply scheme, and it is believed that this scheme will become the development trend of the water supply industry.
2 Traditional water supply system
1. Water supply system with a single constant speed pump
Water supply mode: the pump directly feeds the water from the reservoir into the water supply pipe network, and the pump runs at a constant speed from the beginning of the system to the stop of the water supply;
Advantages: simple system and low cost;
Disadvantages: Unstable pressure in the pipeline network, high energy consumption, and large waste of water resources.
2. Water supply system with fixed speed pump and water tower
Water supply mode: the water is fed into the water tower by the water pump, and then the water tower supplies water to the pipe network. When the water level in the water tower is lower than a certain position, the water pump starts to work, and when the water level is lower than a certain position, the water pump stops working;
Advantages: Compared with the previous water supply method, the water supply pressure is relatively constant, and the energy consumption is relatively small;
Disadvantages: large equipment investment, large floor space, non-adjustable water pressure, frequent start and stop of water pumps cause high equipment losses.
3. Water supply system with constant speed pump and air pressure tank
Water supply mode: the water is fed into the air pressure tank by the water pump, and then the air pressure tank supplies water to the pipe network. When the air pressure in the air tank is lower than a certain pressure, the water pump starts to work, and when the air pressure in the air tank is higher than a certain pressure, the water pump stops working;
Advantages: lower cost than the water tower method;
Disadvantages: The frequent start and stop of the water pump will cause large losses to the equipment and high energy consumption.
3 Technical Features of HD31
HD31 inverter uses advanced customized design concepts, focuses on the needs of the water supply industry, and perfectly combines advanced motor control technology with constant pressure water supply control logic; rich water supply control logic functions, super overload capacity, perfect fault protection, It can meet the energy-saving transformation and application of various water supply systems.
3.1 Abundant water supply control logic functions
(1) 2 water supply modes
The constant pressure water supply debugging mode is mainly used to detect the wiring of the motor wiring and the wiring of the inverter output terminal;
The constant pressure water supply operation mode is a mode that must be selected during the constant pressure water supply operation.
(2) Water level detection function
The water level detection includes 3 modes: the water level signal is not detected, input by the switch input terminal, and input by the analog input terminal. The water level detection function mainly realizes the monitoring of the water level of the reservoir, and adopts different water supply measures according to different situations. When the water level drops, when the water level drops to the lower limit water level, the system operates according to the standby set pressure. If the water level drops to the water shortage level, the system will stop all currently running pumps; when the water level rises, the system restarts when the water level rises to the lower limit water level. Start the water pump to start water supply and supply water according to the standby pressure at this time. If the water level rises to the upper limit water level, the system will supply water according to the normal pressure.
(3) Water pump rotation function
The water pump rotation function is to solve the situation that some water pumps are in a long-term shutdown state and even rust occurs when the water supply system has a stable water supply pressure for a long time.
(4) Sleep function
The sleep function occurs when the current water supply system monitors that the pressure of the water supply pipe network has been exceeding the expected set pressure, and the variable frequency pump is still in the lower limit frequency and will output zero frequency. If sleep at this time, it will save power. After the network pressure drops, the system will wake up again to continue water supply.
(5) Multi-period setting of water supply pressure
Multi-period set pressure water supply is suitable for residential water supply, for example, where there are obvious differences in water consumption in different periods of time.
(6) PID function
Regarding the set pressure signal input to the water supply system and the feedback pipe network pressure signal, the system's pipe network pressure eventually tends to the set pressure through the PID adjustment characteristics.
3.2 Super overload capacity
150% rated output current for 2 minutes;
180% rated output current for 10 seconds;
3.3 Perfect fault protection
When the inverter reports a fault, the water supply system will deal with it according to the preset processing method. The system contains two processing methods, one is that if the inverter reports a fault, all the pumps in the water supply system are directly stopped, and the other is that the system will switch to the next inverter pump when the inverter reports a fault.
4 Application case of constant pressure water supply
4.1 Site conditions and wiring
Three asynchronous motors, a remote pressure gauge with a DC0-10V range of 1Mpa, a potentiometer with a 0-10v range, and a liquid level sensor are used on site. The desired pipe network pressure is set by the potentiometer signal, and the remote pressure gauge signal The actual pressure of the current pipe network is fed back to the HD31, and the liquid level sensor monitors the current water volume information of the reservoir. The information returned by HD31 through the liquid level sensor determines whether the current system continues to pump water from the reservoir. When the water in the reservoir is sufficient, HD31 uses the built-in PID function to calculate the potentiometer signal and the remote pressure gauge signal to achieve the desired pipe network pressure. The wiring is shown in Figure 1:
1.1 Debugging process
(1) Wiring according to Figure 1 above;
(2) Enable the water supply extension function and enable the water supply extension card;
(3) Set the rated current of water pump 1 according to the motor nameplate;
(4) Set the command given channel;
(5) Set acceleration and deceleration time, analog function, terminal function;
(6) Adjust the two analog signals, and adjust the PID parameters according to the actual performance.
1.2 Parameter setting
1.3 Debugging effect
After setting the desired pipe network pressure, start the constant pressure water supply system. Through the built-in PID function of HD31, the water pump 1 is quickly adjusted from 0Hz to the PID upper limit frequency operation. At this time, the desired pipe network pressure has not been reached. According to the preset deceleration time, the device will immediately reduce the PID upper and lower frequency to the lower limit frequency. At the same time, the pump 2 will be put into use in the power frequency mode, and then the pump 1 will run again at the frequency adjusted by the PID. At this time, observe the feedback from the remote pressure gauge. The signal is basically stable within our pre-set pipe network pressure range.
5 Concluding remarks
A variety of pressure setting methods meet the needs of various projects, the advanced PID adjustment function ensures the stability of the pipe network pressure, and the water level control function ensures that the water supply is suspended when the reservoir water is insufficient. On the one hand, it saves energy and reduces on the other The mechanical loss and dormancy control functions ensure that all pumps are shut down to save energy when the pressure in the pipe network continues to be too high. Practical use shows that HD31 achieves a good constant pressure water supply. Its excellent motor performance, rich control functions, and stable and reliable performance have finally won the recognition of customers. HD31 will continue to make its due contribution to energy saving and emission reduction in the water supply industry. .