Publish Time: 2022-07-06 Origin: Site
The AC motor cannot realize speed regulation by changing the voltage, it must realize the speed regulation by changing the frequency. A frequency converter is an adjustable frequency device that uses an adjustable frequency to change the speed of an AC motor.
A frequency converter is a power control device that converts a power frequency power supply into another frequency by using the on-off function of a power semiconductor device. First, the power frequency AC power is converted into DC power through the rectifier, and then the DC power is converted into AC power with controllable frequency and voltage to supply the motor.
1. Frequency conversion energy saving
The energy saving of the frequency converter is mainly manifested in the application of fans and water pumps. After the fan and pump load adopts frequency conversion speed regulation, the power saving rate is 20% to 60%. This is because the actual power consumption of the fan and pump load is basically proportional to the cube of the rotation speed. When the average flow required by the user is small, the fan and pump use frequency conversion speed regulation to reduce the speed, and the energy saving effect is very obvious. The traditional fans and pumps use baffles and valves to adjust the flow, the motor speed is basically unchanged, and the power consumption does not change much. According to statistics, the electricity consumption of fans and pump motors accounts for 31% of the national electricity consumption and 50% of the industrial electricity consumption. It is very important to use the variable frequency speed control device on such loads. At present, the more successful applications are the variable frequency speed regulation of constant pressure water supply, various types of fans, central air conditioners and hydraulic pumps.
2. Realize motor soft start
The hard start of the motor will not only cause a serious impact on the power grid, but also require too much capacity of the power grid. The large current and vibration generated during startup will greatly damage the damper and valve, and it will be extremely detrimental to the service life of equipment and pipelines. After using the inverter, the soft start function of the inverter will make the starting current change from zero, and the maximum value will not exceed the rated current, which reduces the impact on the power grid and the requirements for power supply capacity, and prolongs the service life of equipment and valves. , and also save the maintenance cost of the equipment.
3. Application in improving process level and product quality
The frequency converter can also be widely used in various mechanical equipment control fields such as conveying, lifting, extrusion and machine tools. It can improve the technological level and product quality, reduce the impact and noise of the equipment, and prolong the service life of the equipment. After adopting the frequency conversion speed control, the mechanical system is simplified, the operation and control are more convenient, and some can even change the original process specification, thus improving the function of the whole equipment. For example, in the setting machine used in textiles and many industries, the temperature inside the machine is adjusted by changing the amount of hot air fed into it. The circulating fan is usually used to convey the hot air. Since the speed of the fan remains unchanged, the amount of hot air sent can only be adjusted by the damper. If the damper adjustment fails or is adjusted improperly, the setting machine will be out of control, thus affecting the quality of the finished product. When the circulating fan starts at high speed, the wear between the transmission belt and the bearing is very serious, making the transmission belt a consumable item. After adopting variable frequency speed regulation, temperature regulation can be realized by automatically adjusting the speed of the fan through the frequency converter, which solves the problem of product quality. In addition, the frequency converter can easily start the fan at low frequency and low speed and reduce the wear between the transmission belt and the bearing, which can also prolong the service life of the equipment and save energy by 40%.
4. Application in automation system
Since the inverter has a built-in 32-bit or 16-bit microprocessor, it has a variety of arithmetic logic operations and intelligent control functions, the output frequency accuracy is 0.1%-0.01%, and it is equipped with perfect detection and protection links. Therefore, in automation widely used in the system. For example: winding, drawing, metering and wire guide in chemical fiber industry; flat glass annealing furnace, glass kiln stirring, edge drawing machine, bottle making machine in glass industry; automatic feeding and batching system of electric arc furnace and intelligent control of elevator Wait. The application of frequency converters in CNC machine tool control, automobile production lines, papermaking and elevators has changed to improve the technological level and product quality.
5. Easy to control and remote control
The operating system of the inverter is simple and the selectivity is high. The user can control the inverter to start from zero to increase the speed evenly, and can also choose different acceleration modes (such as straight line, S-shaped line, automatic, etc.). During the operation of the motor, the speed can be adjusted at any time as needed, and the response speed is fast, and it can also be connected to the PLC system to achieve remote control.
6. Protect motor components when stopped
The inverter can not only protect the motor when it starts, but also has a good protective effect when the motor stops running. When the motor is stopped, the internal components will vibrate violently, which will increase the friction between the bearings or gears, waste energy and reduce the service life. The inverter has various shutdown control methods, such as uniform deceleration stop, automatic stop, DC braking and other methods can be selected at will, which can greatly reduce the loss between the various parts of the motor and improve the service life. In addition, because the damage to the motor components is small, the stability factor of the entire system is greatly increased.