Frequency converter main circuit is to provide asynchronous motor power transform part of the power supply, inverter main circuit can be roughly divided into two categories:
1: voltage is the voltage source converter for AC inverter, DC filter is the capacitance of the circuit.
2, the current type is a DC into AC current source inverter, DC loop filter is inductive.

Frequency converter can be divided into four main parts:

1, Rectifier: it is connected with a single-phase or three-phase AC power, generate a pulsating DC voltage. Rectifier—there are two basic types of controllable and uncontrollable.
2, intermediate circuit: it has the following three types:
1.rectifier voltage into DC current.
2.The pulsating DC voltage becomes stable or smooth, for use by the inverter.
3.Fixed the rectified DC voltage into DC voltage variable
3, the inverter: it produces motor voltage frequency, in addition, some fixed DC voltage inverter can also be transformed into a variable AC voltage.
4, control circuit: it transmits signals to a rectifier, intermediate circuit and inverter, it also receives signals from this part.