Abstract : This paper discusses the practical significance and principle of using variable frequency speed control (VFD) technology to achieve energy conservation in light of China's current power shortage situation, and introduces the selection method for VFDs. Keywords : Variable frequency speed control technology; VFD; Energy conservation. The motor capacity of fans, pumps, mixers, and compressors used in China's mining, petroleum, metallurgy, and light textile industries accounts for approximately 50% of the total electrical drive capacity nationwide. Most of these motors use asynchronous motors for constant-speed operation, with motor capacity selected based on the maximum load. However, in actual operation, these devices typically regulate flow by adjusting dampers and valves, resulting in significant energy consumption by the motors. Statistics show that in 1995, the total installed capacity of fans and pumps in China reached 160 million kW, with an annual power consumption of 320 billion kWh. If VFD control were applied to all these loads, energy savings could exceed 20%, effectively alleviating the current power supply shortage and significantly improving economic efficiency. [b]1. Principle of Energy Saving Using Variable Frequency Speed ​​Regulation Technology 1.1 Principle of Variable Frequency Speed ​​Regulation[/b] According to the speed formula of an asynchronous motor, n=60f/[P(1-s)], when the slip s does not change much, the speed n of the asynchronous motor is directly proportional to the frequency f of the stator power supply. Therefore, by continuously changing the frequency of the stator power supply, the speed of the asynchronous motor can be smoothly adjusted. In practical applications, in order to obtain good variable frequency speed regulation performance, while changing the frequency, the stator phase voltage U is made to change according to different laws, so as to achieve constant torque or constant power speed regulation to adapt to the requirements of different loads. Common asynchronous motor variable frequency speed regulation systems (i.e., frequency converters) are divided into four types: ① AC-DC-AC variable frequency speed regulation system with open-loop speed regulation, which has a simple structure, low price, and high reliability, but slightly poor speed regulation accuracy and dynamic quality; ② Vector transformation variable frequency speed regulation system with open-loop speed regulation, where the torque can be directly controlled, and the static and dynamic quality is greatly improved; ③ Vector transformation variable frequency speed regulation system with closed-loop speed regulation, which has a wide speed regulation range, high speed regulation accuracy, and excellent dynamic quality. However, the price is high; ④ Open-loop AC-AC variable frequency speed control systems have complex structures, small speed ranges, and low operating speeds. [b][align=center]For more details, please click: Variable Frequency Speed ​​Control Technology and Energy Saving Research[/align][/b]