Function of frequency converter

1. Frequency conversion energy saving

Energy saving of frequency converter is mainly reflected in the application of fans and water pumps. After variable frequency speed regulation is adopted for fan and pump loads, the power saving rate is 20% - 60%, because the actual power consumption of fan and pump loads is basically proportional to the third power of speed. When the average flow required by users is small, fans and pumps adopt variable frequency speed regulation to reduce their speed, and the energy-saving effect is very obvious. The traditional fans and pumps use baffles and valves for flow regulation, the motor speed is basically unchanged, and the power consumption changes little. According to statistics, the power consumption of fan and pump motors accounts for 31% of the national power consumption and 50% of the industrial power consumption. It is of great significance to use variable frequency speed regulation devices on such loads. At present, the more successful applications are constant pressure water supply, various fans, central air conditioning and variable frequency speed regulation of hydraulic pumps.

2. Application in automation system

Because the frequency converter has built-in 32-bit or 16 bit microprocessor, has a variety of arithmetic and logic operations and intelligent control functions, the output frequency accuracy is 0.1%~0.01%, and is equipped with perfect detection and protection links, it is widely used in the automation system. For example: winding, stretching, metering and wire guide in chemical fiber industry; Flat glass annealing furnace, glass kiln mixing, edge drawing machine and bottle making machine in the glass industry; Automatic charging and batching system of electric arc furnace and intelligent control of elevator, etc. The application of frequency converter in CNC machine tool control, automobile production line, papermaking and elevator.

3. Application in improving process level and product quality

Frequency converter can also be widely used in transmission, lifting, extrusion, machine tool and other mechanical equipment control fields. It can improve the process level and product quality, reduce the impact and noise of equipment, and extend the service life of equipment. After adopting frequency conversion speed regulation control, the mechanical system is simplified, and the operation and control are more convenient. Some can even change the original process specifications, thereby improving the function of the whole equipment. For example, in the setting machine used in textile and many industries, the temperature in the machine is adjusted by changing the amount of hot air. The circulating fan is usually used for conveying hot air. As the fan speed remains unchanged, the amount of hot air sent can only be adjusted by the damper. If the damper fails to adjust or is not adjusted properly, the setting machine will be out of control, thus affecting the quality of finished products. When the circulating fan starts at high speed, the wear between the drive belt and the bearing is very severe, making the drive belt a consumable. After adopting frequency conversion speed regulation, the 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, reduce the wear between the drive belt and the bearing, prolong the service life of the equipment, and save 40% energy at the same time.

4. Realize soft start of motor

The hard start of the motor will not only cause serious impact on the power grid, but also have too high requirements on the capacity of the power grid. The large current and vibration generated during the start-up will cause great damage to the baffle and valve, and will be extremely detrimental to the service life of equipment and pipelines. After using the frequency converter, the soft start function of the frequency converter will change the starting current 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, extends the service life of equipment and valves, and saves equipment maintenance costs.

Working principle of frequency converter

Function, principle and application of frequency converter.jpg

The frequency converter is mainly composed of rectifier (AC to DC), filter, inverter (DC to AC), braking unit, driving unit, detection unit, microprocessor unit, etc. The frequency converter adjusts the voltage and frequency of the output power supply by switching off the internal IGBT, and provides the required power supply voltage according to the actual needs of the motor, so as to achieve the purpose of energy saving and speed regulation. In addition, the frequency converter has many protection functions, such as overcurrent, overvoltage, overload protection, etc. With the continuous improvement of industrial automation, frequency converters have also been widely used.

The main circuit is the power conversion part that provides voltage and frequency regulation power supply for asynchronous motor. The main circuit of frequency converter can be divided into two categories: voltage type is the frequency converter that converts the DC of voltage source into AC, and the filter of DC circuit is capacitance. Current mode is a frequency converter that converts the DC of current source into AC, and its DC circuit filter is inductance. It consists of three parts, the "rectifier" that converts the power frequency power supply into DC power, and the smoothing circuit that absorbs the voltage pulsation generated by the converter and inverter.