Abstract : This paper introduces the electrical control principle and process parameter settings of the MICROMASTER 440 frequency converter applied to a spinning frame, and conducts comparative experiments. Practice shows that frequency conversion control of the main motor of the spinning frame can improve production efficiency. Keywords : spinning frame; frequency converter; yarn breakage rate; energy consumption. With the increasing degree of mechatronics, AC variable frequency synchronous speed control systems are widely used in the transmission control of textile machinery. Spinning is the last process in the spinning process. In spinning production, yarn breakage is a key factor affecting product quality, output, and energy consumption. The essence of yarn breakage is that when the strength of the yarn in the spinning section between the current roller and the guide hook is less than the tension borne by the spinning section, breakage occurs. Therefore, to reduce yarn breakage, it is necessary to stabilize the spinning tension. Our company uses the Siemens MICROMASTER 440 frequency converter to control the main motor of the spinning frame. During the spinning process, different speeds are set according to different stages of small, medium, and large yarns to stabilize the spinning tension and increase the speed of the spinning machine, thereby improving production efficiency. 1. Control Principle During the spinning process, the tension of the small yarn is high, the tension of the medium yarn is low and stable, while the tension of the large yarn increases. This tension variation pattern determines the distribution pattern of most yarn breakage in the small yarn, least in the medium yarn, and slightly more in the large yarn. High breakage in the small yarn limits the increase in machine speed, while low breakage in the medium yarn prevents the machine from reaching its speed potential, thus affecting machine production efficiency. Therefore, adjusting the machine speed can balance spinning tension and reduce breakage; that is, the machine speed should be reduced when the tension is high and increased when the tension is low. Using a frequency converter to control the speed of the spinning frame achieves the goal of balancing spinning tension. The machine speed is adjusted based on the tension changes and yarn breakage distribution patterns of the small, medium, and large yarn sections. Positioning is determined by the rising and falling position of the steel spool plate in three time periods: the first position is at the bottom of the small yarn tube after forming; the second position is at the medium yarn section; and the third position is at the large yarn section (above 2/3 of the tube length). A proximity switch transmits a signal to the frequency converter based on the steel spool plate's position. After CPU processing and calculation, the frequency is changed according to the set process output parameters, thereby adjusting the main motor speed and controlling the machine speed. The control principle is shown in Figure 1. [b][align=center]For more details, please click: Practice of Frequency Conversion Control for Main Motor of Spinning Frame[/align][/b]