Application of Sunwoele VFD (Variable-frequency Drive) in boiler fan energy-saving renovation

At present, among all kinds of mechanical and electrical equipment in all walks of life in China, the motors matched with fans and pumps account for about 60% of the country's installed motor capacity, and the power consumption accounts for about one-third of the country's total power generation. It is particularly worth mentioning that most fans and water pumps have the phenomenon of large horses and small carts during use. In addition, due to changes in production and technology, it is necessary to frequently adjust the flow, pressure, and temperature of gases and liquids; In fact, this is to meet the requirements of process and working conditions for gas and liquid flow regulation by artificially increasing resistance, and at the cost of wasting electric energy and money. This backward adjustment method not only wastes precious energy, but also has poor adjustment accuracy, which makes it difficult to meet the requirements of modern industrial production and service, and has serious negative effects.

The appearance of frequency conversion speed controller has brought a revolution to the way of AC speed regulation. With the continuous improvement and development of frequency conversion technology in the past ten years. The performance of frequency conversion speed regulation is becoming more and more perfect, and it has been widely used in AC speed regulation in different fields. It has brought considerable economic benefits to enterprises and promoted the automation process of industrial production.

Frequency conversion speed regulation is used for speed regulation of AC asynchronous motors, and its performance far exceeds any previous AC and DC speed regulation methods. Moreover, the structure is simple, the speed regulation range is wide, the speed regulation precision is high, the installation and commissioning is convenient, the protection function is perfect, the operation is stable and reliable, and the energy saving effect is remarkable. It has become the latest trend of AC motor speed regulation.

1. The principle of frequency conversion energy saving:

1. Fan operating curve

Using VFD (Variable-frequency Drive) to control the fan is a power-saving method to reduce aerodynamic force. Compared with the commonly used method of adjusting the damper to control the air volume, it has an obvious power-saving effect.

The power saving principle can be explained from the diagram:

In the figure, the curve (1) is the wind pressure-air volume (H-Q) characteristic of the fan at a constant speed n1, and the curve (2) is the wind resistance characteristic of the pipe network (the damper is fully opened). Curve (4) is the frequency conversion operating characteristics (throttle fully open)

Assume that the fan works at point A with the highest efficiency. At this time, the wind pressure is H2, the air volume is Q1, and the shaft power N1 is proportional to the product of Q1 and H2, which can be represented by the area AH2OQ1 in the figure. If the production process requires, the air volume needs to be reduced from Q1 to Q2. At this time, the method of adjusting the damper is equivalent to increasing the resistance of the pipe network, so that the resistance characteristic of the pipe network changes to curve (3), and the system changes from the original working point A to the new working point B. It can be seen from the figure that the wind pressure increases instead, and the shaft power is proportional to the area BH1OQ2. Apparently, the shaft power does not drop much. If the VFD (Variable-frequency Drive) speed control method is adopted, the fan speed is reduced from n1 to n2. According to the proportional law of the fan parameters, the air volume (Q—H) characteristics at the speed n2 are drawn, as shown in the curve (4). It can be seen that in the case of satisfying the same air volume Q2, the wind pressure H3 is greatly reduced, and the power N3 is significantly reduced, which is represented by the area CH3OQ2. The saved power △N=(H1-H3)×Q2 is represented by the area BH1H3C. Obviously, the economic effect of energy saving is very obvious.

2. Energy-saving rate of fans at different frequencies

The fan is a mechanical device that transmits gas, and the water pump is a mechanical device that transmits liquid. Both of them are a kind of machinery that converts the shaft power of the motor into the mechanical energy of the fluid. The working principles of the two are basically the same.

According to the principle of fluid mechanics, the air volume of the fan and the water pump