Abstract : This paper introduces the working principle, selection, and specific application and role of frequency converters in rotary kiln drive systems. Keywords : Frequency converter, rotary kiln Currently, all major frequency converter manufacturers worldwide have adopted digital technology, resulting in simpler main circuits and more complete control circuits. In particular, the application of vector control technology in frequency converters has decoupled the stator current and excitation current of AC motors, allowing independent control of each component of the AC motor, similar to controlling a DC motor. Since the 1990s, frequency converters have been widely used in various industries, achieving significant economic benefits in cement plants and yielding many successful examples and experiences. 1. Working Principle and Capacity Selection of Frequency Converters The working principle of a frequency converter is to convert the industrial frequency AC power into DC power through a rectifier, and then convert the DC power into AC power with a controllable frequency through an inverter. Regarding the speed regulation of electric motors, we know that the synchronous speed expression of an AC motor is: n = 60f(1-s)/p (1) where n is the speed of the asynchronous motor; f is the frequency of the asynchronous motor; s is the slip of the motor; and P is the number of pole pairs of the motor. From equation (1), we can see that there are three ways to change the speed of an electric motor: changing the frequency of the rotating magnetic field f, changing the slip, and changing the number of pole pairs P. A frequency converter utilizes the direct proportionality between speed and frequency, and achieves motor speed regulation by changing the power supply frequency. When the frequency changes within the range of 0-50Hz, the motor speed regulation range is very wide. Therefore, a frequency converter is an ideal high-efficiency, high-performance speed regulation method. [b][align=center]For more details, please click: Application of Variable Frequency Speed ​​Regulation Technology in Rotary Kiln Drive System[/align][/b]