Introduction to frequency converter

The principle of the frequency converter is the principle of applying frequency conversion technology and microelectronics technology to control the power control equipment of the AC motor by changing the frequency of the working power of the motor.

The power supply we use is divided into AC power supply and DC power supply. The general DC power supply is mostly obtained by the AC power supply through transformer transformer, rectification and filtering. AC power accounts for about 95% of the total power used by people.
Whether it is used in homes or factories, the voltage and frequency of single-phase AC power and three-phase AC power have certain standards according to the regulations of various countries. For example, according to the regulations of mainland China, the direct user single-phase AC voltage is 220V, three-phase The AC line voltage is 380V and the frequency is 50Hz. The power supply voltage and frequency of other countries may be different from our country. For example, single-phase 100V / 60Hz, three-phase 200V / 60Hz, etc., standard voltage and frequency AC power supply The power supply is called industrial frequency AC.

Generally, a device that converts a fixed-frequency and constant-frequency AC power into an AC power with a variable voltage or frequency is called an “inverter.”

In order to generate variable voltage and frequency, the device must first convert the alternating current of the power supply to direct current (DC), a process called rectification.
The general inverter is an inverter power supply that inverts the DC power supply to a certain frequency and a certain voltage. We call inverters with adjustable inverter power frequency and voltage.

The output waveform of the frequency converter is a simulated sine wave, which is mainly used in the speed regulation of three-phase asynchronous motor, also called frequency converter.

For variable frequency inverters that require waveforms that are mainly used in instrumentation and testing equipment, the waveforms must be organized to output standard sine waves, called variable frequency power supplies. The frequency conversion power supply is 15–20 times the price of the inverter.

Inverters can also be used in home appliances. Among home appliances that use inverters, not only motors (such as air conditioners, etc.), but also fluorescent lamps and other products.

The frequency converter used for motor control can change both voltage and frequency. However, the frequency converter used for fluorescent lamps is mainly used to adjust the frequency of power supply.
The working principle of the inverter is widely used in various fields. For example, the power supply of the computer power supply. In this application, the inverter is used to suppress reverse voltage, frequency fluctuations and instantaneous power failure.

The frequency converter mainly adopts the AC-DC-AC method (VVVF frequency conversion or vector control frequency conversion). First, the power frequency AC power is converted into a DC power through a rectifier, and then the DC power is converted into an AC power with frequency and voltage control to supply electric motor.

The frequency converter is mainly composed of rectification (AC to DC), filtering, inverter (DC to AC), braking unit, drive unit, detection unit micro-processing unit, etc.