Frequency inverter is a kind of circuit that uses power electronic device to change AC from 50Hz to other frequencies and includes AC/AC and AC/DC/AC types.

• 变频是指利用电力电子器件将50Hz的交流电变换为用户所要求频率的交流电，它分为直接变频(交-交变频)和间接变频(交-直-交变频)。