Abstract : This paper introduces the use of frequency converters to adjust fan speed and change air volume to control humidity. A relative humidity sensor is installed in the workshop using pulse width modulation (PWM) speed control. The measured relative humidity signal is transmitted to a transmitter, which compares the emitted electrical signal with the given relative humidity. The difference is transmitted to the PWM control section of the inverter, which controls the inverter's on/off state via base drive, thus achieving the frequency conversion effect. The fan speed changes with the motor speed, thereby changing the air volume and adjusting the relative humidity in the workshop. Keywords : Textile air conditioning system; frequency converter; relative humidity; speed. With climate changes, the quality of cotton yarn and fabric is greatly affected by the air volume of the textile air conditioning system. The task of textile air conditioning is to maintain a certain temperature, humidity, airflow speed, and cleanliness in the workshop to meet the requirements of textile production and labor protection. The heat in the textile workshop changes with the outdoor climate; only by timely adjusting the quality and quantity of the supplied air can the workshop air maintain a suitable relative humidity. To maintain the yarn in a dehumidified state in the fine spinning workshop, the relative humidity in the coarse spinning workshop should be controlled at a higher level, while the relative humidity in the fine spinning workshop should be controlled at a lower level, ensuring that the yarn core is moist inside and dry outside. This guarantees yarn strength and is beneficial for spinning. 1. Fan Speed ​​Adjustment Method The air volume supplied L = Q₀ (I₀ - I₁), where Q₀ is the heat of the workshop, I₀ is the enthalpy of the air in the workshop, and I₁ is the enthalpy of the air supplied to the workshop. When the heat of the workshop Q₀ changes, the air volume L can be adjusted (quantity adjustment), the enthalpy of the supplied air I₁ can be changed (quality adjustment), or both L and I₁ can be adjusted simultaneously (mixed adjustment). The simplest adjustment method is to change the fan speed accordingly based on the change in workshop heat Q[sub]0[/sub], thereby changing the air volume L. The fan speed range should be appropriate, the initial investment should be economical, the mechanical performance should be good, the energy-saving effect should be good, the operation and management should be convenient, and the power grid interference should be minimal. While cascade speed regulation and frequency conversion speed regulation have better speed range, mechanical performance, and energy-saving effect, cascade speed regulation is only suitable for wound rotor motors and pollutes the power grid. Frequency conversion speed regulation has a higher initial investment, but it has the advantages of a large speed range, good mechanical performance, good energy-saving effect, and high technological content. The air conditioning system in the textile branch of Qiqihar Zhongtian Textile Co., Ltd. uses a dual-speed motor for speed regulation. If a frequency converter could be used for stepless speed regulation, the air volume could be better regulated, and air could be supplied according to the workshop's residual heat. 2. Principle of Frequency Conversion Speed ​​Regulation Speed ​​regulation of synchronous motors can be achieved by changing the power supply frequency and the number of electrode pairs; speed regulation of asynchronous motors is achieved by changing the power supply frequency, the number of motor pairs, and the slip rate. Variable frequency speed control (VFD) is a method of speed regulation that changes the motor speed by altering the frequency of the power supply. It largely retains the inherent characteristics of asynchronous motors, namely high rigidity and small speed difference. Therefore, VFD offers advantages such as high efficiency, wide speed range, high precision, and smooth speed regulation. VFD is divided into three types: voltage-based VFD, current-based VFD, and pulse-width modulation (PWM) VFD. The main circuit of a PWM VFD is shown in Figure 1. [b][align=center]For more details, please click: Application of Variable Frequency Drive in Textile Air Conditioning Systems[/align][/b]