A frequency converter (formerly also a frequency converter) is a device that is used to convert an electric current with a certain frequency into an electric current with another frequency. A very common reason for using a frequency converter is the need for continuous speed control of an asynchronous electric motor, but also to save electricity! These converters have undergone rapid development since the late 1960s. In particular, the development of microprocessor and semiconductor technology, as well as the price of these components, have led to great advances in the arrangement and functions of frequency converters. However, the basic principles remained the same. The frequency converter can be divided into four main parts: rectifier, intermediate circuit, inverter and microcomputer control.