According to the principle of fluid dynamics, there is a great correlation between the air volume of the centrifugal fan and the rotating speed power of the motor: the air volume of the centrifugal fan is proportional to the speed of the fan, and the wind pressure is proportional to the square of the speed of the fan. The axial power of the fan is equal to the product of the air volume and the wind pressure, so the axial power of the fan is also proportional to the third power of the speed of the fan. With the continuous improvement, development and progress of frequency conversion technology in recent years. Centrifugal fan has been widely used in many fields because of its more and more developed performance of variable frequency speed regulation, which saves energy to a large extent and has been widely used in many fields. The energy-saving benefits obtained by the energy-saving method of fan frequency conversion bring a lot of economic benefits to enterprises in various industries and greatly promote the development process of automation of social industrial production.
1. Principle of Frequency conversion and Energy Saving of centrifugal Fan
At present, most fan equipments are driven directly by asynchronous motor to realize the energy saving of fan. There are some defects and problems in this way, for example, the characteristic of electrical protection is poor, and the starting current is too large. Produce mechanical shock, etc. When the load of the motor is too large, it will affect to a certain extent, reduce the service life of the equipment, and lead to some mechanical faults, such as the burning and burning of the motor, and so on.
Fan variable-frequency governor is a new type of energy-saving product in modern society. Under the condition that the curve of pipeline performance is not changed, variable speed regulation can change the performance curve of fan by changing speed, and then change its working point. Fan variable frequency governor has many advantages, such as easy operation, high control precision, high performance, no maintenance and so on. Under the condition that other conditions are not changed, it is the basic principle of the fan variable frequency speed regulation technology to change the fixed position of the asynchronous motor and input the frequency of the power supply at the sub-end to change the speed of the motor. The relationship between motor speed and input frequency of working power supply is proportional: n / p, n is used to represent rotational speed, f is used to denote input frequency, s is used to denote motor slip rate, and p is used to denote motor pole logarithm. The control of the outlet baffle will increase the wind resistance when the opening degree is reduced, so it is not suitable to adjust the air volume in a wide range. The control of inlet baffle is relatively wider than that of outlet baffle, and the shaft power under the condition of decreasing opening is reduced in proportion to the air volume, but it is still not comparable to the energy saving effect of variable frequency speed regulation.
Normally, it is considered that the running air volume is not the rated air volume of the fan design, if the throttling control is used to adjust, the resistance of the pipe network is changed by reducing the opening of the air door, and the curve of the pipe network characteristics becomes steeper. Increase the pressure by causing the flow rate at the operation point to decrease; In the way of speed control, the resistance of the pipe network is constant when the baffle is fully opened. If the air volume is the same, it is necessary to reduce the speed and pressure of the fan.
2. Problems of Frequency conversion and Energy Saving of centrifugal Fan
In the production process of enterprises in various industries, the application of fan is more common, the traditional throttling mode is mainly carried out by the use of diversion, resulting in the fan has no higher operating efficiency, As a result, a great deal of waste of energy is caused, and the cost of maintenance and maintenance of the fan increases the production cost of the enterprise to a certain extent. The control of air volume of centrifugal fan mainly depends on the baffle of fan inlet, which will not only waste a lot of energy, but also cause the vibration of fan to be bigger, the noise is higher, and the negative pressure in the furnace of equipment is not stable enough. It is easy to appear fever phenomenon and many other bad conditions. The amount of steam used in the actual production process of the enterprise is relatively small. In general, contactors are used to control the blast and draft air of the boiler, frequent start-up and stop cause waste of a lot of energy and instability of operation and so on.www.jnblower.com