There are many types of inverters, which can be classified according to different methods. First: According to the frequency of the inverter output AC power, it can be divided into power frequency inverter, intermediate frequency inverter and high frequency inverter. The frequency of the power frequency inverter is 50-60 Hz; the frequency of the intermediate frequency inverter is generally 400 Hz to ten kHz; the frequency of the high frequency inverter is generally more than ten kHz to MHz. Second: According to the number of phases of the inverter output, it can be divided into single-phase inverter, three-phase inverter and multi-phase inverter. Third: According to the direction of the output of the inverter, it can be divided into active inverter and passive inverter. The inverter that transmits the electric energy output from the inverter to the industrial power grid is called an active inverter; any inverter that outputs the electric energy output from the inverter to a certain electric load is called a passive inverter. Device. Fourth: According to the form of the main circuit of the inverter, it can be divided into single-ended inverter, push-pull inverter, half-bridge inverter and full-bridge inverter. Fifth: According to the type of inverter main switching device, it can be divided into thyristor inverter, transistor inverter, field effect inverter and insulated gate bipolar transistor (IGBT) inverter. It can be classified into two categories: “half-controlled” inverter and “full control” inverter. The former does not have the self-shutdown capability, and the components lose control after being turned on. Therefore, the “half-controlled” common thyristor belongs to this category; the latter has self-shutdown capability, ie, no device. The turn-on and turn-off can be controlled by the gate, so it is called "full control type", and the power field effect transistor and the insulated gate dual-effect transistor (IGBT) belong to this category. Sixth: According to the DC power supply, it can be divided into voltage source inverter (VSI) and current source inverter (CSI). In the former, the DC voltage is nearly constant, and the output voltage is an alternating square wave; the latter, the DC current is nearly constant, and the input current is an alternating square wave. Seventh: According to the waveform of the inverter output voltage or current, it can be divided into sine wave output inverter and non-sine wave output inverter. Eighth: According to the inverter control method, it can be divided into a frequency modulation (PFM) inverter and a pulse width modulation (PWM) inverter. Ninth: According to the working mode of the inverter switching circuit, it can be divided into a resonant inverter, a fixed frequency hard switching inverter and a fixed frequency soft switching inverter. Tenth: According to the inverter commutation method, it can be divided into load commutating inverter and self-converting inverter.