把工频电源(50Hz或60Hz)变换成各种频率的交流电源，以实现电机的变速运行的设备。其中控制电路完成对主电路的控制，整流电路将交流电变换成直流电，直流中间电路对整流电路的输出进行平滑滤波，逆变电路将直流电再逆变成交流电。对于如矢量控制变频器这种需要大量运算的变频器来说，有时还需要一个进行转矩计算的CPU以及一些相应的电路。

Convert the power supply (50Hz or 60Hz) to the ac power of various frequencies to realize the operating speed of the motor. The control circuit to complete the control of the main circuit, rectifier circuit will be alternating current into direct current, dc intermediate circuit to smooth filtering of the output of the rectifier circuit, inverter circuit dc inverter again into alternating current. For a converter that requires a large amount of computation, such as vector control, sometimes a cpus and corresponding circuits are required for torque calculations. 

The rectifier, which is connected to a single phase or three-phase ac power supply, produces a pulsating dc voltage. 

2、中间电路，有以下三种作用：

Intermediate circuits have the following three functions: 

a、使脉动的直流电压变得稳定或平滑，供逆变器使用。

A, to make the pulsating dc voltage stable or smooth for use by inverters. 

b、通过开关电源为各个控制线路供电。

B, power supply for each control circuit by switching power supply. 

c、可以配置滤波或制动装置以提高变频器性能。

C, can configure filter or brake device to improve the performance of frequency converter. 

3、逆变器，将固定的直流电压变换成可变电压和频率的交流电压。

Inverter, which transforms fixed dc voltage to variable voltage and frequency voltage. 

4、控制电路，它将信号传送给整流器、中间电路和逆变器，同时它也接收来自这些部分的信号。其主要组成部分是：输出驱动电路、操作控制电路。主要功能是：

The control circuit, which sends the signal to the rectifier, the intermediate circuit and the inverter, and also receives the signal from these parts. Its main components are: output drive circuit, operation control circuit. The main features are: 

a、利用信号来开关逆变器的半导体器件。

A, the semiconductor devices that use signals to switch inverters. 

b、提供操作变频器的各种控制信号。

B, provide various control signals for operating the frequency converter. 

c、监视变频器的工作状态，提供保护功能。

C, monitor the working condition of the frequency converter, provide protection function.