Learn how to set up a constant pressure water supply inverter at a glance

As the country's investment in the water supply industry increases, the level of automation in water plant operations continues to improve, and the application of PLC in the water supply industry is gradually increasing.

The constant pressure water supply inverter uses PLC as the central control unit, and uses the inverter and PID to quickly adjust the working pressure of the water supply system according to the system status to achieve the purpose of constant pressure water supply, improve the working stability of the system, and obtain good results.

control effect and obvious energy saving effect.

Some special constant pressure water supply inverters also have certain waterproof and dustproof capabilities.

Let the editor introduce to you the relevant knowledge of constant pressure water supply inverter and the setting method of constant pressure water supply inverter.

1. The working principle of the constant pressure water supply inverter is based on the user's requirements. The water supply pressure value is first set, and then powered on. The pressure sensor monitors the pipe network pressure and converts it into an electrical signal and sends it to the programmable controller or microcomputer controller for analysis and processing.

, transmit the signal to the frequency converter to control the operation of the water pump. When the water consumption increases, the output voltage and frequency increase, the pump revolutions increase, and the water output increases. When the water volume decreases, the water pump revolutions decrease, reducing the water output.

, so that the pressure of the pipe network is maintained at the set pressure value. When multiple pumps are running, the soft start is performed one by one, from the variable frequency to the power frequency until the pressure and flow rate are satisfied, thus realizing the circulation control of the water pump. When running with a small flow rate at night, it can

The frequency conversion water pump is used to maintain work, and the frequency conversion water pump can be shut down to maintain pressure.

2. Control principle of constant pressure water supply inverter 1. Principle of speed regulation AC motor speed characteristics: n=60f(1-s)/p, where n is the motor speed, f is the AC frequency, s is the slip rate, and p is the pole

logarithm.

After the motor is selected, s and p are fixed values, and the motor speed n is proportional to the alternating current frequency f. Using a frequency converter to change the alternating current frequency can achieve variable frequency stepless speed regulation of the motor.

2. According to the load working principle of the centrifugal pump, it can be seen that the flow rate is proportional to the rotational speed: Q∝N The torque is proportional to the square of the rotational speed: T∝N2 The power is proportional to the cube of the rotational speed: P∝N3 And the frequency conversion speed regulation itself

The energy loss is extremely low. At various speeds, the input power of the frequency converter is almost equal to the motor shaft power. From this, it can be seen that when using variable frequency speed regulation technology to supply water, the relationship between flow changes and power in the system: P variable = N3P amount = Q3P amount is adopted.

The way the outlet valve controls the flow, when the motor is running at industrial frequency, the relationship between the flow change and the power in the system: P valve = (0.4+0.6Q) P amount, where P is the power, N is the rotation speed, Q is the flow rate, for example, set the current flow rate

is 60% of the rated flow of the water pump, then when using variable frequency speed regulation, P variable = Q3P amount = 0.216P amount, and when using valve control, P valve = (0.4 + 0.6Q) P amount = 0.76P amount, power saving = (P

Valve-P change)/P valve*100%=71.6%.

It can be seen from the theoretical calculation results that the energy saving effect is very significant, and in actual operation, the variable frequency constant pressure water supply technology in the community has obvious advantages such as automatic control of constant pressure and no pollution compared with the traditional pressurized water supply system.

Flow%100%90%80%70%60%50%Power saving rate%0%22.5%41.8%61.5%71.6%82.1% Moreover, the new residential frequency conversion constant pressure water supply system can automatically control one or more main pumps and one

operation of the dormant pump.

When the water consumption in the pipe network is reduced to about 1/6-1/8 of the flow rate of a single main pump, the system automatically stops the main pump and starts the low-power dormant pump to ensure the system's low-flow water supply and solve the problem of low-flow or even zero-flow water supply.

This solves the problem of wasting a large amount of electric energy and further saves energy from operation control.

According to the feedback principle: If you want to maintain a physical quantity unchanged or basically unchanged, you should compare this physical quantity with a constant value to form a closed-loop system.

If we want to keep the water pressure constant, we must introduce the water pressure feedback value to compare with the given value to form a closed-loop system.

However, the characteristics of the controlled system are nonlinear and large inertia systems. In the method of combining control and PID, fuzzy control is used to speed up the response when the pressure fluctuation is large; PID is used to maintain static accuracy when the pressure range is small.

This algorithm can be realized through PLC and intelligent instruments, and at the same time, the PLC can be programmed to switch between the power frequency and variable frequency of the pump.

Practice has proved that this method is feasible and the cost is not high.

In order to maintain the pressure of the water supply network unchanged, a pressure transmitter is installed as a feedback element in the management of the pipe network system according to the feedback theorem. Since the water supply system has long pipes and large diameters, the pressure filling of the pipe network is slow, so

The system is a large lag system, which is not easy to be controlled directly by the PID regulator. Instead, the PLC is used to participate in the control to achieve the adjustment effect on the control system.

3. Characteristics of constant-pressure water supply inverter 1. Power saving: The most significant advantage of the variable-frequency constant-pressure water supply system is energy saving, which is usually 10-40%.

From the perspective of energy saving of a single water pump, the smaller the flow rate, the greater the energy saving.

Optimized energy-saving control software enables the water pump to achieve maximum energy-saving operation.