变频器是应用变频技术与微电子技术，通过改变电机工作电源频率方式来控制交流电动机的电力控制设备。
Frequency converter is the application of frequency conversion technology and microelectronic technology to control the power control equipment of AC motor by changing the frequency mode of motor power supply.
变频器主要由整流（交流变直流）、滤波、逆变（直流变交流）、制动单元、驱动单元、检测单元微处理单元等组成。变频器靠内部IGBT的开断来调整输出电源的电压和频率，根据电机的实际需要来提供其所需要的电源电压，进而达到节能、调速的目的，另外，变频器还有很多的保护功能，如过流、过压、过载保护等等。随着工业自动化程度的不断提高，变频器也得到了非常广泛的应用。
Frequency converter is mainly composed of rectification (AC variable DC), filtering, inverter (DC to AC), brake unit, drive unit, detection unit, micro processing unit and so on. Inverter by internal IGBT drive voltage and frequency off to adjust the output power, the power supply voltage required to provide according to the actual needs of the motor, so as to achieve the purpose of speed, energy saving, in addition, there are a lot of protection drive, such as over-current, over-voltage, overload protection and so on. With the continuous improvement of the degree of industrial automation, the frequency converter has also been widely used.