Abstract : This paper discusses the potential problems arising from the retrofitting and application of high-voltage variable frequency speed control systems in the main blower of the sulfuric acid industry. The energy-saving effect and control operation after use are analyzed. Keywords : High-voltage variable frequency drive, main blower retrofitting and application 1. Introduction AC variable frequency speed control technology is a new type of electric drive speed control technology that developed rapidly in the 1980s. Variable frequency speed control devices are used for speed control of AC asynchronous motors. Their performance surpasses any other AC speed control method (such as voltage reduction speed control, pole changing speed control, slip speed control, series pole speed control, etc.). Due to its significant energy-saving benefits, high speed control accuracy, wide speed range, comprehensive protection functions, and advantages such as easy automatic control, safe and reliable operation, and simple installation, use, and maintenance, it has been widely used in various industries, becoming the latest trend in AC motor speed control. Especially in recent years, the application of high-voltage variable frequency drives has become increasingly widespread, and the energy-saving potential of enterprises will be fully developed. 2. Main Fan Operation Status Specific parameters are as follows: Rated Voltage: 10KV; Rated Power: 630KW; Rated Current: 42A. During normal production, sulfuric acid production is significantly affected by system and conversion temperature variations. Therefore, the air volume required for combustion in the sulfur-burning boiler also varies considerably. Frequent adjustment of the inlet and outlet valve openings is necessary. When system malfunctions necessitate starting and stopping the main fan, the inlet and outlet valves and return valve must also be switched on and off, resulting in a heavy workload for operators. Furthermore, when the converter heats up, low airflow operation of the main fan leads to significant energy loss. During normal operation, the fan opening is approximately 50%, i.e., inlet opening 40 degrees, outlet opening 30 degrees, return 10 degrees; current 32A; actual fan power 500KW; fan flow rate 26000 cubic meters per hour; fan pressure approximately 23Kpa. [Read more : High-Voltage Frequency Converter Speed ​​Regulation Retrofit and Application in Main Fans of the Sulfuric Acid Industry]