Frequency converters are power control devices that use frequency conversion technology and microelectronics technology to control AC motors by changing the frequency of the motor's working power supply.
Frequency converters are mainly composed of rectification (AC to DC), filtering, inversion (DC to AC), braking units, drive units, detection units, and microprocessing units. The frequency converter adjusts the voltage and frequency of the output power supply by the internal IGBT's disconnection, and provides the required power supply voltage according to the actual needs of the motor, thereby achieving 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 the degree of industrial automation, frequency converters have also been widely used.
Application scenarios
1. Frequency conversion energy saving
Frequency converter energy saving is mainly reflected in the application of fans and water pumps. Fans and pumps use frequency conversion speed regulation to reduce their speed, and the energy saving effect is very obvious.
2. Application in automation system
The inverter has a built-in 32-bit or 16-bit microprocessor, with a variety of arithmetic logic operations and intelligent control functions, an output frequency accuracy of 0.1%~0.01%, and is equipped with a complete detection and protection link. Therefore, it is widely used in automation systems.
3. Application in improving process level and product quality
The inverter can also be widely used in various mechanical equipment control fields such as transmission, lifting, extrusion and machine tools. It can improve process level and product quality, reduce equipment impact and noise, and extend the service life of equipment.
4. Realize motor soft start
The hard start of the motor will not only cause serious impact on the power grid, but also require too high power grid capacity. The large current and vibration generated during startup will cause great damage to the baffle and valve, and are 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, extends the service life of equipment and valves, and also saves equipment maintenance costs.
Variable frequency power supply
Variable frequency power supply converts the AC power in the mains into AC→DC→AC, and outputs a pure sine wave. The output frequency and voltage are adjustable within a certain range. It is different from the variable frequency speed controller used for motor speed regulation, and also different from the ordinary AC voltage regulator.
The characteristics of an ideal AC power supply are stable frequency, stable voltage, zero internal resistance, and a pure sine wave voltage waveform (no distortion). Variable frequency power supply is very close to the ideal AC power supply. Therefore, advanced and developed countries are increasingly using variable frequency power supply as a standard power supply to provide the best power supply environment for electrical appliances and facilitate objective assessment of the technical performance of electrical appliances. There are two main types of variable frequency power supply: linear amplification type and SPWM switching type.
Application scenarios
1. Power supply for precision electronic products
Due to the inconsistency of power grid indicators in various countries around the world, export electrical appliance manufacturers need power supplies to simulate the power grid conditions of different countries, and provide engineers with pure, reliable, low harmonic distortion, high stable frequency and voltage regulation rate sine wave power output in design and development, production line testing and quality assurance product testing, life, over-high voltage/low voltage simulation testing and other applications.
Mainly used for power consumption detection and debugging of electrical products for export by manufacturers or export traders, and for power supply of precision instruments.
2. Industrial automation industry
After the 1970s, the development of large-scale integrated circuits and computer control technology, as well as the application of modern control theory, have gradually enabled AC power traction systems to have good technical performances such as wide speed regulation range, high steady speed range, high steady speed accuracy, fast dynamic response, and reversible operation in four quadrants, which can be comparable to DC power traction in terms of speed regulation performance.
In AC speed regulation technology, variable frequency speed regulation has an absolute advantage, and its speed regulation performance and reliability are constantly improving, and its price is constantly decreasing. In particular, variable frequency speed regulation has obvious power saving effect, and it is easy to realize process automation, which is deeply favored by the industrial industry.
Difference between frequency converter and variable frequency power supply
After-sales
Frequency converter: Because frequency converters are mostly purchased from other manufacturers specializing in frequency converters, once a problem occurs, the power supply manufacturer will dismantle the frequency converter and send it back to the frequency converter manufacturer (some are abroad), the maintenance cycle is long, and the frequency converter manufacturer will not be responsible for the matching of the frequency converter with the transformer and the LC low-pass filter circuit. Even on-site repairs can hardly guarantee a complete solution to the problem.
Variable frequency power supply: The manufacturer develops and produces it by itself and is very familiar with the power supply. Once a problem occurs, the problem will be solved at the power supply site in the shortest time.
Reliability
Frequency converter: The shore power supply assembled by the frequency converter is relatively simple to produce. Because its main part "frequency converter" is purchased, it is difficult to ensure that the parameters of the frequency converter and other components match.
Variable frequency power supply: The overall design of the power supply is coordinated. After years of technical accumulation, the power supply is guaranteed to operate stably and reliably.
Safety
Frequency converter: The frequency converter is designed specifically for variable frequency starting of motors. When starting, the voltage and frequency rise synchronously. The power supply modified with it may affect the electrical equipment, especially the frequency converter, controlled rectifier, communication equipment, etc.
Variable frequency power supply: The frequency is constant during the startup process. Shore power can provide pure, reliable, low harmonic distortion, highly stable voltage and frequency sine wave power output, which is very close to the ideal AC power supply.
Three-phase unbalance
Inverter: The inverter adopts △ inversion. Although the output is converted into Y-type output through the transformer, it has poor adaptability to three-phase unbalanced loads, which may increase the reverse torque in the motor, increase the motor temperature, reduce efficiency, increase energy consumption, cause vibration, and output loss.
Inverter power supply: The inverter part adopts a star type, each phase can be independently loaded, and adapt to three-phase completely unbalanced loads. The unbalance degree can be within 3%.
