With the continuous improvement of urban water supply quality and reliability of water supply systems, utilizing advanced water pump control technology and supporting high-performance and energy-saving variable frequency control systems has become an inevitable trend in water supply systems.
1. The application of frequency converter in water pumps
According to the speed regulation formula n=60f/p, it is not difficult to see that the change in f (frequency) is directly related to n(speed). Adjusting n (speed) by changing f(frequency) is considered the best speed regulation method currently. The current frequency converters mainly adopt an AC-DC-AC method, which first converts single-phase or three-phase AC voltage into DC voltage through a rectifier (consisting of 6 diodes in a full wave rectifier bridge), and then converts DC voltage into AC voltage with controllable frequency and voltage through an inverter (consisting of 6 IGBTs).
The frequency converter mainly consists of three parts: the main circuit part (rectifier, smoothing circuit, inverter), the control circuit part (calculation circuit, detection circuit, driving circuit, protection circuit), and the power component.
2. The advantages and energy-saving effect of frequency converters
2.1 Soft Start
After using a frequency converter, due to a smooth change in frequency, the speed smoothly increases from 0 to reach the corresponding speed. Therefore, the motor current is smooth and has no impact, reducing the impact of starting current on the motor and power grid, and extending the service life of the equipment.
2.2 Reducing reactive power
Due to the large capacity of filtering capacitors inside the frequency converter, the power factor is close to 1, which increases the active power. After using the frequency converter, reactive power compensation equipment is no longer set, which not only improves the power factor but also reduces equipment investment.
2.3 Simple control and high degree of automation
It can achieve forward and reverse function conversion of the motor, and the frequency is adjustable. It also operates stably and reliably, and can achieve PID closed-loop control. It can be connected to PLC and automatically control the operation of the frequency converter.
2.4 Energy conservation
Set the frequency as needed, and the water pump can generally be adjusted based on parameters such as pressure and flow. When operating below the power frequency and meeting the water supply demand, energy-saving effects can be achieved. When setting the V/F curve as a quadratic curve, energy-saving can also be achieved. When the operating frequency f=25Hz, V1 is much lower than V2, and according to the electricity formula, electricity=UxlxT. When the current l and time T are constant, and U is small, less electricity is used. Therefore, the output voltage of the quadratic V/F curve is low, achieving energy-saving.
Post time: Apr-06-2023